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91.
Silvia Pede Luciano Galantini Camillo La Mesa Donatella Capitani Anna Laura Segre 《Colloid and polymer science》2007,285(10):1067-1075
Solutions containing a polyoxy-ethylene/polyoxy-propylene/polyoxy-ethylene (PEO–PPO–PEO) block copolymer, indicated as F68,
in water were investigated as a function of composition and temperature. Hydrogen nuclear magnetic resonance (1H NMR) line width, chemical shift, self-diffusion, spin-lattice relaxation times, laser light scattering and rheological methods
were used. The monomer–micelle equilibrium and the micelle–liquid crystalline phase transitions depend on the F68 content
in the mixture and temperature. Significant changes in light scattering intensity and apparent hydrodynamic radius are associated
to micelle formation above the critical micellar temperature (CMT). According to a Contin analysis, this behaviour is reflected
in the presence of two populations in the intensity–intensity autocorrelation functions. The contributions due to molecules
and micelles can be evaluated separately. No such effects are observed below the CMT. Micelle onset is also associated to
variations in 1H NMR spectra, affecting the chemical shift, line width and spin-lattice relaxation time of the PPO methyl protons and self-diffusion,
as well. Spin-lattice relaxation times of PEO chains, conversely, change significantly at temperatures close to the micelle–liquid
crystalline thermal transition. Similar results were obtained from the line width of 2H NMR spectra as a function of T. Significant changes in both viscous and elastic modulus were also observed and ascribed to PPO dehydration, at the CMT,
as well as to squeezing and dehydration of PEO units in liquid crystal formation, respectively. 相似文献
92.
93.
Mediterranean Journal of Mathematics - Given a Lattice of Hilbert spaces V J and a symmetric operator A in V J , in the sense of partial inner product spaces, we define a generalized resolvent for... 相似文献
94.
Dynamics of DNA adsorption on and release from SDS-DDAB cat-anionic vesicles: a multitechnique study
Bonincontro A Falivene M Mesa CL Risuleo G Peña MR 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):1973-1978
DNA adsorption and release from cat-anionic vesicles made of sodium dodecylsulfate-dodecyldimethylammonium bromide (SDS-DDAB) in nonstoichiometric amounts was investigated by different electrochemical, spectroscopic, and biomolecular strategies. The characterization of the vesicular system was performed by dynamic light scattering, which allowed estimating both its size and distribution function(s). The interaction dynamics was followed by dielectric spectroscopy and zeta-potential, as well as by agarose gel electrophoresis, AGE. Also, circular dichroism, CD, measurements were carried out, to ascertain possible structural rearrangements of DNA, consequent to the interactions with the cat-anionic vesicles. CD demonstrates that vesicle-bound DNA retains its native conformation. The results obtained by the aforementioned techniques are consistent and indicate that binding saturation is obtained at a [DNA/vesicles] charge ratio close to 0.8, considering only the excess surface charges on the vesicles. This result is apparently in contradiction with a purely electrostatic approach and is tentatively ascribed to the distance between charges on the biopolymer and the vesicle surface, respectively. A possible interpretation is discussed. The nucleic acid can be completely retrieved from the vesicles upon addition of adequate amounts of SDS, which is the defective surfactant in the vesicular system. Precipitation of the poorly soluble SD-DDA salt results in an almost complete release of DNA. 相似文献
95.
We show the existence of continuous periodic solutions of the 3D incompressible Euler equations which dissipate the total kinetic energy. 相似文献
96.
In this article we partially answer two open questions concerning clean rings. First, we demonstrate that if a quasi-continuous module is strongly clean then it is Dedekind-finite. Second, we prove a partial converse. We also prove that all clean decompositions on submodules of continuous modules extend to the entire module. 相似文献
97.
We propose to determine the displacement field u: I?R→R of a 1-D bar extended in a hard device by minimizing a non-local energy functional of the type $$[u]: = \int_\mathcal{I} {U\;} \left( {u'(x) + \frac{1}{K}\sum\limits_{x_i \in J_u } {[u](x_i )} \;\rho (x - x_i )} \right)\;{\text{d}}x + \sum\limits_{x_i \in J_u } {\varphi ([u](x_i )),} $$ where K is a material parameter, [u](x i ) denotes the jump of u at x i and J u ? I the set of all jump points. For appropriate choices of the bulk energy U(?), of the surface energy ?(?) and of the weight function ρ(?), we prove an existence theorem for minimizers in the space SBV(I) of special bounded variation functions and we qualitatively discuss their form by investigating the corresponding Euler–Lagrange equations. We show that for sufficiently large values of the bar elongation, minimizers of the energy are discontinuous and, most of all, the non-local term [u](x i )ρ(x?x i ) influences the relative position among the jump points, a finding that is of crucial importance to reproduce the experimental evidence. 相似文献
98.
Stefano Bianchini Camillo De Lellis Roger Robyr 《Archive for Rational Mechanics and Analysis》2011,200(3):1003-1021
In this paper we study the regularity of viscosity solutions to the following Hamilton–Jacobi equations In particular, under the assumption that the Hamiltonian \({H\in C^2({\mathbb R}^n)}\) is uniformly convex, we prove that D x u and ? t u belong to the class SBV loc (Ω).
相似文献
$\partial_{t}u+H(D_{x}u)=0\quad\hbox{in }\Omega\subset{\mathbb R}\times{\mathbb R}^{n}.$
99.
Ilaria Giuseppina Occhiuto Roberto Zagami Mariachiara Trapani Maria Angela Castriciano Andrea Romeo Luigi Mons Scolaro 《Molecules (Basel, Switzerland)》2020,25(23)
Under mild acidic conditions, various metal derivatives of tetrakis(4-N-methylpyridinium)porphyrin (gold(III), AuT4; cobalt(III), CoT4; manganese(III), MnT4 and zinc(II), ZnT4) catalytically promote the supramolecular assembling process of the diacid 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4) into J-aggregates. The aggregation kinetics have been treated according to a well-established model that involves the initial formation of a critical nucleus containing m porphyrin units, followed by autocatalytic growth, in which the rate evolves as a power of time. An analysis of the extinction time traces allows to obtain the rate constants for the auto-catalyzed pathway, kc, and the number of porphyrins involved in the initial seeding. The aggregation kinetics have been investigated at fixed H2TPPS4 concentration as a function of the added metal derivatives MT4. The derived rate constants, kc, obey a rate law that is first order in [MT4] and depend on the specific nature of the catalyst in the order AuT4 > CoT4 > MnT4 > ZnT4. Both resonance light scattering (RLS) intensity and extinction in the aggregated samples increase on increasing [MT4]. With the exception of AuT4, the final aggregated samples obtained at the highest catalyst concentration exhibit a negative Cotton effect in the J-band region, evidencing the occurrence of spontaneous symmetry breaking. The role of the nature of the metal derivative in terms of overall charge and presence of axial groups will be discussed. 相似文献
100.
Fluorinated block copolymers composed of a polystyrene (Sx) first block and a polyacrylate second block carrying hydrophobic/lipophobic perfluorohexyl side chains (AF) were prepared by atom transfer radical polymerization (ATRP). Fluorescence emission properties were imparted to the copolymers by incorporation in the second block of a julolidine-based fluorescent molecular rotor (JCBF). The synthesized block copolymers were used as the fluorescent low-surface energy thin top-layer onto a polystyrene bottom-layer to produce novel two-layer film vapochromic sensors. Contact angle and X-ray photoelectron spectroscopy (XPS) measurements revealed that the two-layer film surfaces were hydrophobic and lipophobic at the same time and highly enriched in fluorine content as a result of the effective segregation of the perfluorinated tails to the polymer-air interface. The fluorescence intensity of the two-layer films decreased significantly when they were exposed to vapours of organic solvents, including tetrahydrofurane, chloroform, and trifluorotoluene. However, an AF content-dependent sensing behaviour was also observed, with the two-layer films containing the copolymer with the shorter fluorinated block giving a more rapid and almost quantitative decrease in fluorescence variation. Fluorescence emission of the films was also proved to vary with temperature. Both the vapochromic and thermochromic responses were reversible after successive solicitation cycles. The fluorescence variation of the two-layer films was much more marked than that of the corresponding PS/JCBF blend, thus providing a system potentially applicable as highly sensitive volatile organic compound (VOC) sensor, thanks to the active role of the fluorinated block in promoting the migration of the fluorophore to the outermost surface layers. 相似文献