In situ and frontal polymerization for the consolidation of porous stones: a unilateral NMR and magnetic resonance imaging study

Consolidation treatment of porous materials was performed by in situ and frontal polymerization of acrylic monomers inside a porous stone. To study the penetration of the polymer inside the stone and its consolidating effects we used water as a contrast agent, detecting its penetration using unilateral NMR and magnetic resonance imaging. All data obtained on differently treated stones were compared with corresponding ones obtained analyzing both untreated stones and stones simply painted with a well-known polymeric protective agent. In situ polymerization of acrylic monomers inside porous stones has been demonstrated to be an extremely powerful consolidating method, whereas thermally initiated frontal polymerization seems less efficient. In both cases the optimal choice of monomers is still open and requires further study. Our data indicate that unilateral NMR represents an inexpensive and simple technique for the non-invasive observation of the water uptake and of the effect of consolidation procedures in porous materials.     

Twisted sums with spaces

If is a separable Banach space, we consider the existence of non-trivial twisted sums , where or For the case we show that there exists a twisted sum whose quotient map is strictly singular if and only if contains no copy of . If we prove an analogue of a theorem of Johnson and Zippin (for ) by showing that all such twisted sums are trivial if is the dual of a space with summable Szlenk index (e.g., could be Tsirelson's space); a converse is established under the assumption that has an unconditional finite-dimensional decomposition. We also give conditions for the existence of a twisted sum with with strictly singular quotient map.

     

Solution- and solid-phase synthesis of 4-hydroxy-4,5-dihydroisoxazole derivatives from enantiomerically pure N-tosyl-2,3-aziridine alcohols

[reaction: see text] Enantiomerically pure N-tosyl-2,3-aziridine alcohols are directly converted into 4-hydroxy-4,5-dihydroisoxazole 2-oxides through oxidation to the corresponding aldehydes followed by in situ tandem nitroaldol-intramolecular cyclization. This study was concerned with (i) the selection of a suitable aziridine activation, (ii) the preparation of the target 4-hydroxy-4,5-dihydroisoxazole derivatives in solution, and (iii) the elaboration of a solid-phase process using hydroxy Merrifield-supported nitroacetic acid ester.     

Monitoring the Evolution of Asynchrony between Mean Arterial Pressure and Mean Cerebral Blood Flow via Cross-Entropy Methods

Cerebrovascular control is carried out by multiple nonlinear mechanisms imposing a certain degree of coupling between mean arterial pressure (MAP) and mean cerebral blood flow (MCBF). We explored the ability of two nonlinear tools in the information domain, namely cross-approximate entropy (CApEn) and cross-sample entropy (CSampEn), to assess the degree of asynchrony between the spontaneous fluctuations of MAP and MCBF. CApEn and CSampEn were computed as a function of the translation time. The analysis was carried out in 23 subjects undergoing recordings at rest in supine position (REST) and during active standing (STAND), before and after surgical aortic valve replacement (SAVR). We found that at REST the degree of asynchrony raised, and the rate of increase in asynchrony with the translation time decreased after SAVR. These results are likely the consequence of the limited variability of MAP observed after surgery at REST, more than the consequence of a modified cerebrovascular control, given that the observed differences disappeared during STAND. CApEn and CSampEn can be utilized fruitfully in the context of the evaluation of cerebrovascular control via the noninvasive acquisition of the spontaneous MAP and MCBF variability.     

Physical and Chemical Characterization of Cellulose Based Textiles Modified by Periodate Oxidation

Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state ¹³C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method.     

Testing Homotopy for Paths in the Plane

In this paper we present an efficient algorithm to test if two given paths are homotopic; that is, whether they wind around obstacles in the plane in the same way. For paths specified by n line segments with obstacles described by n points, several standard ways achieve quadratic running time. For simple paths, our algorithm runs in O(n log n) time, which we show is tight. For self-intersecting paths the problem is related to Hopcrofts problem; our algorithm runs in O(n ^3/2log n) time.     

Mathematical justification of a nonlinear integro-differential equation for the propagation of spherical flames

This paper is devoted to the justification of an asymptotic model for quasisteady three-dimensional spherical flames proposed by G. Joulin [17]. The paper [17] derives, by means of a three-scale matched asymptotics, starting from the classical thermo-diffusive model with high activation energies, an integro-differential equation for the flame radius. In the derivation, it is essential for the Lewis Number – i.e. the ratio between thermal and molecular diffusion – to be strictly less than unity. If is the inverse of the – reduced – activation energy, the idea underlying the construction of [17] is that (i) the time scale of the radius motion is ^-2, and that (ii) at each time step, the solution is -close to a steady solution.In this paper, we give a rigorous proof of the validity of this model under the restriction that the Lewis number is close to 1 – independently of the order of magnitude of the activation energy. The method used comprises three steps: (i) a linear stability analysis near a steady – or quasi-steady – solution, which justifies the fact that the relevant time scale is ^-2; (ii) the rigorous construction of an approximate solution; (iii) a nonlinear stability argument. Mathematics Subject Classification (2000) Primary 80A25, Secondary 35K57, 47G20     

Structural insights on nanoparticles containing gadolinium complexes as potential theranostic

Nanostructures are gaining interest in drug release applications. Amphiphilic molecules can give, in water solution, a variety of nanostructures as well as thermodynamically stable mesophases three-dimensional inverse cubic structures. These mesophases are attractive candidates for biomedical applications containing extensive water channel networks and could act as very efficient delivery systems of drugs or contrast agents. In order to discover, optimize, and develop these systems, we have performed a deep physicochemical characterization by dynamic light scattering and small-angle neutron scattering of nanoparticles of monoolein (MO) and Pluronic PF127, containing different amounts (1, 5, 10, and 20 %) of the synthetic amphiphilic gadolinium complex (C18)₂DTPA(Gd). Nanoparticle size is found in the 70–400 nm range for all investigated systems; the morphology of the aggregates is driven by the main constituents MO/PF127 and is a mixture of multilayer vesicles and bicontinuous aggregates. Nanostructures are also able to encapsulate doxorubicin (drug-loading content between 70 and 90 % for the different systems) acting as a potential theranostic for simultaneous cancer therapy and MRI visualization.     

Proposal of a two-qutrit contextuality test free of the finite precision and compatibility loopholes

It has been argued that any test of quantum contextuality is nullified by the fact that perfect orthogonality and perfect compatibility cannot be achieved in finite precision experiments. We introduce experimentally testable two-qutrit violations of inequalities for noncontextual theories in which compatibility is guaranteed by the fact that measurements are performed on separated qutrits. The inequalities are inspired by the basic building block of the Kochen-Specker proof of quantum contextuality for a qutrit, despite the fact that their proof is completely independent of it.