N-Alkylamines-Based Micelles Aggregation Number Determination by Fluorescence Techniques

Aggregation numbers of micelles based on N-alkylamines and mixed systems CTACl/N-alkylamines have been determined using fluorescence techniques. The values of aggregation number are compared as a function of hydrocarbon chain length and as a function of the molar fraction in the mixed systems.     

Measurements of the trapped-carriers nonlinearity of commercial semiconductor doped glasses

Interband absorption change dispersions due to the filling of the trapping states are measured in commercial semiconductor doped glasses. The corresponding refractive index changes are obtained through the Kramers-Kronig transformation. Our results indicate a large deep-trapping-states nonlinearity in this material.     

Diffusion of moisture in deformable porous media. Anisotropic fibrous materials

This paper presents a study on the deformation of anisotropic fibrous porous media subjected to moistening by water in the liquid phase. The deformation of the medium is studied by applying the concept of effective stress. Given the structure of the medium, the displacement of the solid matrix is not taken into account with respect to the displacement of the liquid phase. The transport equations are derived from the model proposed by Narasimhan. The transport coefficients and the relation between the variation in apparent density and effective stress are obtained by test measurements. A numerical model has been established and applied for studying drip moistening of mineral wool samples capable or incapable of deformation.Nomenclature D mass diffusion coefficient [L²t^–1] - e void fraction - g gravity acceleration [Lt^–2] - J mass transfer density [ML^–2t^–1] - K hydraulic conductivity [Lt^–1] - K _s hydraulic conductivity of the solid phase [Lt^–1] - K ^* hydraulic conductivity of the deformable porous medium [Lt^–1] - P pressure of moistening liquid [ML^–1 t^–2] - S degree of saturation - t time [t] - V speed [Lt^–1] - X horizontal coordinate [L] - Z vertical coordinate measured from the bottom of porous medium [L] - z z-coordinate [L] Greek Letters porosity - ₁ total hydric potential [L] - _g gas density [ML^–3] - ₁ liquid density [ML^–3] - ₀ apparent density [ML^–3] - _s density of the solid phase [ML^–3] - density of the moist porous medium [ML^–3] - external load [ML^–1t^–2] - effective stress [ML^–1t^–2] - bishop's parameter - matrix potential or capillary suction [L] Indices g gas - 1 moistening liquid - p direction perpendicular to fiber planes - s solid matrix - t direction parallel to fiber planes - v pore Exponent * movement of solid particles taken into account     

An organocatalytic approach to enantiomerically enriched α-arylcyclohexenones and cyclohexanones

The presence of a p-nitrophenyl group converts acetone into an excellent and versatile nucleophile in organocatalytic processes, able to react with α,β-unsaturated aldehydes affording β-substituted α-arylcyclohexenones via a Michael reaction/aldol reaction/dehydration sequence, which occurs in good yields, ee up to 96% and complete diastereoselectivity. The resulting compounds are excellent synthons for the diastereoselective preparation of a variety of synthetically useful polysubstituted cyclohexanones and derivatives.     

Enantioselective organocatalytic formal allylation of α-branched aldehydes

Heteroarylvinyl sulfone 1 has been successfully used as a new sulfonyl Michael acceptor in aminocatalytic reactions with branched aldehydes. Subsequent one-pot Julia-Kocienski olefination allows the challenging preparation of enantiomerically pure α-allylated aldehydes bearing C-α quaternary carbons.     

Giant enhancement of the Raman scattering by local magnon modes in FeF2:Mn2+

A study of the local magnon mode in FeF₂ crystals with Mn²⁺ impurities by inelastic Raman light scattering is presented. Though the interaction between the radiation and the Mn spins is negligible the scattering by the s₀ local mode is very strong. The data of the frequency and the scattering intensity are analyzed in terms of a magnetization coupled mode approach.     

A simple method to find out when an ordinary differential equation is separable

In many statistical discussions, especially in data analysis, the idea of polynomials plays a key role. For example, Dwyer [1] employed polynomials to express factorial moments of discrete distribution in terms of cumulative totals. Traditionally, polynomials are derived using the difference operator method (see [2], p. 134]). In this article, using the differential equation approach as an alternative method, we obtain generalized exponential and logarithmic polynomials, and find their special cases appearing in statistical signal‐noise models.