Interfacial concentrations of chloride and bromide in zwitterionic micelles with opposite dipoles: experimental determination by chemical trapping and a theoretical description

Interfacial concentrations of chloride and bromide ions, with Li(+), Na(+), K(+), Rb(+), Cs(+), trimethylammonium (TMA(+)), Ca(2+), and Mg(2+) as counterions, were determined by chemical trapping in micelles formed by two zwitterionic surfactants, namely N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and hexadecylphosphorylcholine (HDPC) micelles. Appropriate standard curves for the chemical trapping method were obtained by measuring the product yields of chloride and bromide salts with 2,4,6-trimethyl-benzenediazonium (BF(4)) in the presence of low molecular analogs (N,N,N-trimethyl-propane sulfonate and methyl-phosphorylcholine) of the employed surfactants. The experimentally determined values for the local Br(-) (Cl(-)) concentrations were modeled by fully integrated non-linear Poisson Boltzmann equations. The best fits to all experimental data were obtained by considering that ions at the interface are not fixed at an adsorption site but are free to move in the interfacial plane. In addition, the calculation of ion distribution allowed the estimation of the degree of ion coverage by using standard chemical potential differences accounting for ion specificity.     

Generalizations of the Finite Element Method

This paper is concerned with the generalization of the finite element method via the use of non-polynomial enrichment functions. Several methods employ this general approach, e.g. the extended finite element method and the generalized finite element method. We review these approaches and interpret them in the more general framework of the partition of unity method. Here we focus on fundamental construction principles, approximation properties and stability of the respective numerical method. To this end, we consider meshbased and meshfree generalizations of the finite element method and the use of smooth, discontinuous, singular and numerical enrichment functions.     

Spectral invariance of smooth crossed products, and rapid decay locally compact groups

We show that all rapid-decay locally compact groups are unimodular and that the set of rapid-decay functions on a locally compact rapidly decaying group forms a dense and spectral invariant Fréchet *-subalgebra of the reduced group C ^*-algebra. In general, the set of rapid-decay functions on a locally compact strongly rapid-decay group with values in a commutative C ^*-algebra forms a dense and spectral invariant Fréchet *-subalgebra of the twisted crossed product C ^*-algebra. The spectral invariance property implies that the K-theories of both algebras are naturally isomorphic under inclusion.This project is supported in part by the National Science Foundation Grant #DMS 92-04005.     

Die Ursache der Differenzen bei Bestimmung des Silbergehaltes in Bleibarren

Ohne Zusammenfassung     

Ueber die verschiedenen Trennungs- und Bestimmungsmethoden von Baryt und Strontian

Ohne Zusammenfassung     

On the existence of relative values for undiscounted multichain Markov decision processes

The coupled functional equations of undiscounted multichain semi-Markovian decision processes are shown to possess a solution by converting the value equation into the form $\text{v =}\text{max}\text{[w(?) + Π(?)v; ? ? S] ≡ Qv}$ where S is the set of maximal-gain policies and $\text{w(?)}$ is the bias vector associated with policy ?. An elementary proof then shows that the operator Q possesses a fixed point.     

The variational calculus and approximation in policy space for Markovian decision processes

The functional equations of Markovian decision processes yield the state values (and gain rate in the undiscounted case). Variational expressions are exhibited here for these state values (and gain rate); these expressions are stationary when evaluated at the correct values. When guesses for the values (and gain rate) are inserted into these variational expressions, a superior guess is usually obtained. Repetition of this procedure is shown to be equivalent to the method of successive approximations in policy space. Two other unusual features of this procedure are these: when the linear equations determining the Lagrange multipliers are non-singular, the variational expressions for the state variables are precisely one Newton-Raphson iteration; when applied to a linear objective function and piecewise-linear constraints, which arises for the functional equations of Markovian decision processes, the variational test quantity is piecewise constant, i.e., its first variation and higher variations all vanish. The latter explains its good performance (one-step convergence) if good estimates are available.     

On the existence of relative values for undiscounted Markovian decision processes with a scalar gain rate

The functional equations v = max{q(f) ? gT(f) + P(f) v; f?K}  Qv of undiscounted semi-Markovian decision processes are shown to be solvable if and only if all components of the maximum gain rate vector are equal. More generally, in the multichain case, the functional equations for the value vector possess a solution if and only if there is a policy which achieves the maximal gain vector. The method of proof exhibits vectors v^± such that Qv⁺ ? v⁺ and Qv^? ? v^?.     

Gradient expansion of the kinetic energy including nonlocal exchange contributions

We discuss the gradient expansion of the kinetic energy density, explicitly including nonlocal exchange contributions to ordere ². Restricting the expansion to orderh ²2 one finds that the expression obtained in the standard TFDW model is unchanged.