Generalized double involutive geometry of the triangle

We study a generalized geometry of the triangle, based on the idea of letting two arbitrary points play the role that the centroid and the orthocenter play classically. We thus generalize some of the classical results and constructions and also prove some new results in ordinary metric geometry.     

Mass spectral fragmentation studies in usnic acid and related compounds

A study of the fragmentation patterns of the naturally occurring lichen substance, usnic acid (I) and various other chemically and biochemically derived compounds is reported and discussed. From these results it is demonstrated that the characteristic fragmentation patterns observed are of considerable utility in determining not only the substitution patterns on these highly oxygenated molecules, but also the structural elucidation of new compounds within the series.     

Kinetics and mechanism of the decomposition of N-bromoalcoholamines in aqueous solution

The decomposition reactions of N-bromodiethanolamine, N-bromoethylethanolamine, and N-bromomethylethanolamine in aqueous solution have been studied kinetically under various experimental conditions. The results support a proposed reaction mechanism in which the rate controlling step is assumed to be the formation of an imine which is then hydrolyzed to the final decomposition products.     

Influence of dispersion procedure on rheological properties of aqueous solutions of high molecular weight PEO

The linear and nonlinear viscoelastic behaviors of poly(ethylene oxide) (PEO) in aqueous media have been investigated as a function of concentration and molecular weight. A particular interest has been paid to study the effect of turbulent flow under stirring, inducing both shear and elongational stresses, on the rheological behavior of the polymer solutions. The comparison of intrinsic viscosity and viscoelastic properties between shaken and stirred PEO solutions is discussed at the molecular scale in terms of chain scission and aggregation. Results point out that the effect of the mechanical history on the rheological response of PEO solutions depends also on the concentration regime and molecular weight. Indeed, the influence of the dispersion procedure vanishes by decreasing both the concentration and the molecular weight.     

2‐Hydroxyphenyl 2‐methylpyrazolo[1,5‐a]pyrimidin‐6‐yl ketone

The mol­ecules of the title compound, C₁₄H₁₁N₃O₂, form a three‐dimensional soft hydrogen‐bonded network involving C—H?N hydrogen bonds.     

General model for a multimode Nd-doped fiber laser. II: Steady-state analysis of length-dependent polarization effects

We present a steady-state analysis of a general model for a bipolarized Nd-doped fiber laser including the slow longitudinal variations of the dynamical variables. The combined effects of pump-induced, distributed, and localized anisotropies are studied versus the fiber length. In particular, the evolution of the thresholds versus the pump-input polarization angle, for different fiber lengths, is investigated in depth. Approximate analytical results are derived for the thresholds and the output intensities. A good agreement with the numerical simulations is achieved in a large range of parameters.     

Pressure-induced magnetic phase transitions in Yb Kondo lattice systems

In this paper we give a brief overview of the effect of pressure on the magnetic and electronic properties of Yb Kondo lattices using the ¹⁷⁰Yb Mössbauer technique, electrical resistance and X-ray diffraction. The selected materials were either nonmagnetic (YbCu₂Si₂ and Yb₂Ni₂Al) or ferromagnetic (YbNiSn). We show that pressure induces a first order transition to a magnetic ground state in both YbCu₂Si₂ and Yb₂Ni₂Al. In the former compound, the transition is accompanied by a valence change towards Yb³⁺ state. The behavior of both YbCu₂Si₂ and Yb₂Ni₂Al can be understood as resulting from a pressure enhancement of the RKKY interaction which finally dominates the Kondo effect. We demonstrate that the ground state properties of YbNiSn are governed by a volume dependent competition between anisotropic exchange interactions and crystal field anisotropy rather than by a direct competition between Kondo and RKKY interactions.