This electrode is best served cold—a reversible electrochemical lithiation of a gray cubic tin

Journal of Solid State Electrochemistry - The behavior of a cubic allotropic modification of tin (α-Sn) towards lithium electrochemical alloying/de-alloying is reported for the first time. The...     

Polyethylenimine-Containing Cotton Fabrics

Abstract

Polyethylenimine-containing cotton fabrics were prepared by reaction of 1-epoxyethyl-3, 4-epoxycyclohexane with cotton fabric impregnated with polyethylenimine of a moderately high molecular weight. Fabrics with a high unremovable polyethylenimine content and with a different degree of cross-linking were obtained. Adsorption of several heavy metal salts such as mercuric chloride and cupric sulfate by the fabrics was investigated. Adsorption was controlled by polyethylenimine content of the fabric, extent of cross-linking, and the pH of the solution.     

On several variations of the turan and ramsey numbers

We introduce several variations of the Turan and Ramsey numbers, including zero-sum and bounded-average Ramsey numbers. Some interesting relations between these concepts are presented. In particular, a generalization of the k-local Ramsey numbers is established.     

Three-body effective interactions in the f72 region

The three-body effective forces in a pure $\text{(0}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{<mtext>n</mtext>}}$ model space are calculated to second order in perturbation theory. The full effect of the $\text{(0f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{1}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}{}^3$ configuration on the effective interaction in the $\text{(0}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^3$ model space leading to three-body forces is calculated to all orders in G. The resulting three-body force matrix elements come out much weaker than demanded by phenomenological fits. Their main effect is to push the spectra as a whole up in energy, improving the fit of the calculated ground state binding energies with experiment. The biggest three-body-force contribution appears toward the end of the $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell where its main object is to compensate for Pauli violations arising from the two-body diagrams.     

Automata and Square Complexes

We introduce a new geometric tool for analyzing groups of finite automata. To each finite automaton we associate a square complex. The square complex is covered by a product of two trees iff the automaton is bi-reversible. Using this method we give examples of free groups and of Kazhdan groups which are generated by the different states of one finite (bi-reversible) automaton. We also reprove the theorem of Macedońska, Nekrashevych, Sushchansky, on the connection between bi-reversible automata and the commensurator of a regular tree.     

Convergence and perturbation resilience of dynamic string-averaging projection methods

We consider the convex feasibility problem (CFP) in Hilbert space and concentrate on the study of string-averaging projection (SAP) methods for the CFP, analyzing their convergence and their perturbation resilience. In the past, SAP methods were formulated with a single predetermined set of strings and a single predetermined set of weights. Here we extend the scope of the family of SAP methods to allow iteration-index-dependent variable strings and weights and term such methods dynamic string-averaging projection (DSAP) methods. The bounded perturbation resilience of DSAP methods is relevant and important for their possible use in the framework of the recently developed superiorization heuristic methodology for constrained minimization problems.     

Laser-microprobe elemental determinations with an optical multichannel detection system

The results obtained when a laser microprobe is adapted to imaging detectors for multiwavelength detection are described. Detectors evaluated are a silicon-intensified target vidicon and a second-generation photodiode array. Data are presented to illustrate how the combined system can be used to monitor both surface and depth profiles of elemental content of a variety of sample types including a ruby rod and ceramic material with blemishes, electrical capacitors, integrated circuits, and surface-coated electrical conductors. It is also shown how the gating capability of the intensified vidicon can be used to monitor time-dependent changes in the several nanosecond range during the laser microprobe excitation process. Detection limits obtained with both detectors are in the range 2–500 ppm depending on the element, the wavelength used, the matrix, and other variables. The uncertainty associated with the measurement step can be improved by a factor of 2–3 by using ratios of spectral lines. Principal limitations of the laser microprobe method are the nonlinear response of intensity vs. concentration and the resulting need for reference materials with matrices similar to samples for calibration purposes.