47th Session of the ISI: Gastronomie et Paris

Abstract

The Skeptical Environmentalist: Measuring the Real State of the World, by Bjorn Lomborg. Cambridge University Press, 2001. Reviewed by Thomas Wonnacott     

Adsorption and molecular dynamics of low-molecular substances on modified montmorillonite nanoparticles

The effect of the structure of stable nitroxyl radicals on their adsorption from organic solvents on montmorillonite modified with cationic surfactants is examined. The influence of the nature and content of the modifier and solvent, as well as additional modification with cationic dyes, on the adsorption is considered. The kinetic parameters of the adsorption of decane, toluene, and ethanol from the gas phase are determined. The spin probe method is used to determine the phase state and distribution of adsorbed additives, as well as the influence of an additional adsorption of hydrocarbons on the molecular dynamics at the surface of nanoparticles of montmorillonite and nanopigments based on cationic dyes.     

Local dynamics of micelles of new long-chain surfactants in aqueous media

The molecular dynamics, organization, and phase state of aqueous solutions of new long-chain cationic surfactants with saturated hydrocarbon radicals (from C₁₆ to C₂₂) containing one or two hydroxyl groups in their polar heads are studied by the spin-probe EPR spectroscopy. In the region of micellar solutions, local mobility of surfactant molecules slightly changes with an increase in the length of hydrocarbon radical, whereas the order parameter of micelles increases notably. The addition of two hydroxyl groups to the polar part of long-chain (C ₂₂) surfactant molecule considerably decreases local mobility and increases the ordering of micellar system compared to the micelles of analogous surfactant with one hydroxyl group. Phase transition from micellar to a solid state is observed in this system with a decrease in temperature. The addition of KCl to aqueous surfactant solution lowers the local mobility, increases the order parameter of micelles, and can cause changes in the phase state of a system. In the presence of salt, the correlation time of probe rotation and its order parameter depend on surfactant concentration. Apparently, this is explained by changes in the shape of micelles upon variations in surfactant concentration.     

Possible mediators of the "living" radical polymerization

The stable radicals derived from different compounds were detected in process of styrene autopolymerization. The nitroxide radicals are produced from nitrosocompound, hindered hydroxylamine, nitrophenols and nitroanisoles. The phenoxyl radicals are formed from quinine methides, and naphtoxyl radicals are generated from 2-nitro-1-naphtol. The radicals are identified, the kinetics of their formation and follow-up evolution are studied. These radicals can participate in process of living radical polymerization as the mediators and can effect significantly on kinetics of polymerization and structure of the resulting polymer.     

On Hardness and Electronegativity Equalization in Chemical Reactivity Theory

Chemical Reactivity Theory (CRT) contains reactivity indices defined as first and second derivatives of ground-state properties with respect to electron number such as the electronegativity and the hardness. This necessitates use of the Perdew, Parr, Levy, and Balduz (PPLB) version of noninteger density-functional theory (NIDFT) to provide a basis for CRT in DFT. However, the PPLB NIDFT yields ground-state properties which are piecewise linear continuous functions of number, yielding vanishing hardness and staircase electronegativities which do not admit electronegativity equalization. To overcome these difficulties, in the present paper we modify the relationship between CRT and DFT, basing the former on our previously formulated “atoms” in “molecules” theory (AIMT) but retaining the PPLB NIDFT. We recapture electronegativity equalization through the agency of a uniquely defined reactivity potential. We demonstrate that a positive definite hardness matrix can be defined which controls the minimum cost to the AIMT energy functional of internal fluctuations of the electron numbers of the parts of a system.     

On Existence of Mini-Boson Stars

We prove the existence of a countable family of globally regular solutions of spherically symmetric Einstein–Klein–Gordon equations. These solutions, known as mini-boson stars, were discovered numerically many years ago. Received: 14 February 2000 / Accepted: 26 June 2000     

Mathematics and Science Teachers' Use of and Confidence in Empirical Reasoning: Implications for STEM Teacher Preparation

The recent trend to unite mathematically related disciplines (science, technology, engineering, and mathematics) under the broader umbrella of STEM education has advantages. In this new educational context of integration, however, STEM teachers need to be able to distinguish between sufficient proof and reasoning across different disciplines, particularly between the status of inductive and deductive modes of reasoning in mathematics. Through a specific set of mathematical conjectures, researchers explored differences between mathematics (n = 24) and science (n = 23) teachers' reasoning schemes, as well as the confidence they had in their justifications. Results from the study indicate differences between the two groups in terms of their levels of mathematical proof, as well as correlational trends that inform their confidence across these levels. Implications particularly for teacher training and preparation within the context of an integrated STEM education model are discussed.     

Scan clustering: A false discovery approach

We present a method that scans a random field for localized clusters while controlling the fraction of false discoveries. We use a kernel density estimator as the test statistic and adjust for the bias in this estimator by a method we introduce in this paper. We also show how to combine information across multiple bandwidths while maintaining false discovery control.