Green Synthesis of Poly(aminomethylenephosphonic) Acids

The reaction of polyamines with phosphorous acid and formaldehyde in water under focused microwave irradiation provides a facile and rapid synthesis of poly(aminomethylenephosphonic) acids.     

Constant Mean Curvature Foliations of Globally Hyperbolic Spacetimes Locally Modelled on <Emphasis Type="Italic">AdS</Emphasis><Subscript>3</Subscript>

We prove that every three-dimensional maximal globally hyperbolic spacetime, locally modelled on the anti-de Sitter space AdS ₃, with closed orientable Cauchy surfaces, admits a unique CMC time function.     

Fabrication and Properties of Doped Porous Polysiloxane Sol-Gel Layers on Optical Fibers

Polysiloxane porous layers doped with TiO- and phenyl-groups were fabricated by the sol-gel method. Starting sols were prepared from alkoxides using catalysis by HCl or HF. Stable SiO-TiO-sols were obtained by using HF. Porous gel layers with thicknesses of 0.3–1.1 m were coated on fiber surfaces or silicon wafers. Layers with the refractive index of 1.38–1.48 were prepared. The fractional porosity of the layers was estimated to be 0.1–0.35. The interactions of the layers with vapor or liquid chlorinated hydrocarbons, alcohols or aromatic hydrocarbons have been studied in immersing experiments by measuring the output light intensity from the fibers. The observed changes of the output intensity could be correlated to changes of the refractive index of the layer caused by the penetration of the tested chemicals into the layer pores.     

On rigidity of generalized conformal structures

The classical Liouville Theorem on conformal transformations determines local conformal transformations on the Euclidean space of dimension \({\ge }3\) . Its natural adaptation to the general framework of Riemannian structures is the 2-rigidity of conformal transformations, that is such a transformation is fully determined by its 2-jet at any point. We prove here a similar rigidity for generalized conformal structures defined by giving a one parameter family of metrics (instead of scalar multiples of a given one) on each tangent space.     

A comparison of the role of boehmite (AlOOH) and alumina (Al2O3) in the thermal stability and flammability of poly(methyl methacrylate)

In this paper, a comparison of the role of boehmite (AlOOH) and alumina (Al₂O₃) in the thermal stability and flame retardant behaviour of poly(methyl methacrylate) (PMMA) is presented. PMMA–AlOOH and PMMA–Al₂O₃ nanocomposites were prepared by melt blending with different filler contents. These nanocomposites were studied by thermogravimetric analysis (TGA) and cone calorimetry. In the presence of the filler (alumina or boehmite), the thermal stability of the polymer appeared to be significantly improved. An increase of the decomposition temperature of between about 19 and 35 °C was demonstrated by TGA. Cone calorimeter measurements showed that the peak of heat release rate is lowered in the presence of AlOOH or Al₂O₃ in comparison to pure PMMA and that this decrease is higher when the filler content increases. When loading rate is higher (15 wt%), a significant improvement in fire resistance of PMMA was observed in both systems but with two different modes of action.     

Effects of Fine Particles on the Suffusion of Cohesionless Soils. Experiments and Modeling

Internal erosion has long been a major problem associated with earthen structures, and its field investigation has been limited because of its complexity. Laboratory experiments provide a potential insight into the induced processes. Soils suitable to suffusion involve an easy movement of fine particles between the coarse ones. In this study, suffusion experiments were performed on a laboratory column packed with different sand–fines mixtures and subjected to controlled flow conditions. The mixtures are made of Fontainebleau sand (NE34) and fines (kaolinite or illite or silt). The initiation and the progression of soil suffusion were investigated for soil mixtures, and the hydraulic conductivity variation was derived from pressure measurements. Attempts are made to assess the influence of the type and content of fine particles on mixtures suffusion. The results show that among the tested fine particles, illite exhibits a great resistance against suffusion. Fine content increase involves less suitability to suffusion till a threshold value. Recorded pressures indicate that detachment of fines may be followed by clogging in the soil matrix, leading to a decrease of hydraulic conductivity. Furthermore, analytical solutions of simplified mathematical model based on the mass conservation of eroded particles (Govindaraju et al., J Hydrol 172:331–350, 1995) were used to simulate the recorded soil suffusion curves, and the model performance was evaluated. Comparisons between numerical and experimental results indicated a quite good agreement, and allowed the estimation of the model parameters.     

On the Relativistic BGK-Boltzmann Model: Asymptotics and Hydrodynamics

The generalization of the BGK relaxation model to the special relativity setting is revisited here. We deal with several issues related to this relativistic kinetic model which seem to have been overlooked in the previous physical literature, including the unique determination of associated physical parameters, classical, ultra-relativistic and hydrodynamical limits, maximum entropy principles and the analysis of the linearized operator.     

Influence of the nature of the polycation on the adsorption kinetics and on exchange processes in polyelectrolyte multilayer films

The deposition of polyelectrolyte multilayer films (PEMs) appears more and more as a versatile tool to functionalize a broad range of materials with coatings having controlled thicknesses and properties. To increase the control over the properties of such coatings, a good knowledge of their deposition mechanism is required. Since Cohen Stuart et al. (Langmuir 18 (2002) 5607-5612) showed that the adsorption of one polyelectrolyte could induce desorption of polyelectrolyte complexes instead of regular deposition, more and more findings highlight peculiarities in the deposition of such films. Herein we demonstrate that the association of sodium polyphosphate (PSP) as the polyanion and either poly(-L-lysine hydrobromide) (PLL) or poly(allylamine chloride) (PAH) as the polycations may lead to non-monotonous film deposition as a function of time. Complementary, films containing PSP and PLL can be obtained from a (PLL-HA)(n) template films after the exchange of HA (hyaluronic acid) from the sacrificial template by PSP from the solution. This exchange is accompanied by pronounced film erosion. However, when starting from a (PAH-HA)(n) template, the film erosion and exchange due to the contact with PSP is by far less pronounced, nevertheless the film morphology changes. These findings show that the nature of the polycation used to deposit the PEM film may have a profound influence of the film's response to a competing polyanion.     

Kinetic models of chemotaxis towards the diffusive limit: asymptotic analysis

The paper is devoted to the study of the asymptotic behavior of the solutions of a kinetic model describing chemotaxis phenomena. Our interest focuses on the case, where the diffusion part dominates the chemotaxis part in the limit. More in detail, we prove that the solution of kinetic model exists globally and converges to a solution of diffusive limit. Copyright © 2015 John Wiley & Sons, Ltd.