Simultaneous observation of atomic step and domain wall structure of ultrathin Co films by magnetic force microscopy in ultrahigh vacuum

We have applied magnetic force microscopy in ultrahigh vacuum to study the correlation between the atomic step and magnetic domain wall structure of ultrathin Co films prepared in situ on Au(111) substrates. For the first time we were able to achieve high-resolution images showing simultaneously a clear domain wall contrast and the underlying atomic step structure. Although for in-plane magnetized Co films the domain walls were found to run preferentially in a direction perpendicular to the steps, no such correlation could be observed for out-of-plane magnetized Co films. Received: 3 June 1999 / Accepted: 4 June 1999 / Published online: 29 July 1999     

Surface Assisted Nucleation and Growth of Polymer Latexes on Organically-Modified Inorganic Particles

Summary: Polymer latex particles were synthesized in the presence of inorganic particles, which had been organically-modified to promote favorable interactions with growing macromolecules. The organic modification was performed using three different routes: (1) surface covalent grafting of vinyl trialkoxysilanes, (2) surface adsorption of polyethylene glycol-based macromonomers, and (3) bulk modification through ion exchange with cationic monomers or cationic initiators. Two types of mineral particles were studied: commercial and self-prepared silica particles (with diameters from 80 nm to 1 µm), and commercial laponite clay particles with a cation exchange capacity of 0.75 meq · g⁻¹. Emulsion polymerization was performed in the presence of styrene or butyl acrylate monomers. The morphologies of the nanocomposite particles were observed by (cryogenic) transmission electron microscopy and correlated to the organic modification procedure.     

Synthesis of composite latex particles filled with silica

Encapsulation of silica nanoparticles was performed by dispersion polymerization of styrene, butyl acrylate and butyl methacrylate in aqueous alcoholic media. Following previous works^1‐3), the silica beads were first modified by reacting on their surface the 3‐trimethoxysilyl propyl methacrylate coupling agent (MPS). In every case, the silica beads are all surrounded by polymer giving composite latex particles filled with silica. Each composite particle contains from one to a great number of silica beads. Changing the size or the concentration of the silica beads, and the experimental conditions for the synthesis of the polymer particles enables to control this number. One can take benefit of this to synthesize model composite particles with controlled compositions.     

Hybrids and biohybrids as green materials for a blue planet

There is an urgency to identify novel technological answers to the decreasing availability of important resources together with increasing accumulation of pollution. Among the many ways materials science can contribute to these issues, the enhanced use of renewable resources, the optimal production of alternative energies and the improved monitoring/cleaning of contaminated environments can be identified as area where the sol–gel technology has, and will have, a major role to play. In this short review, we more specifically illustrate recent developments in biohybrid chemistry applied to bioplastics, biofuel cells, biosensors and bioremediation.     

Electromigration of trace quantities of radioelements in free electrolyte solutions. Hydrolysis of tetravalent and pentavalent vanadium

The hydrolytic behavior of trace quantities of tetra- and pentavalent vanadium has been studied by the zone electrophoresis method in a wide pH range (2–12). For the first time, the mobilities of all hydrolytic vanadium forms were determined in dilute nitric acid solutions of ionic strength 0.1M at 298 K.     

Two Heuristics for the Euclidean Steiner Tree Problem

The Euclidean Steiner tree problem is to find the tree with minimal Euclidean length spanning a set of fixed points in the plane, allowing the addition of auxiliary points to the set (Steiner points). The problem is NP-hard, so polynomial-time heuristics are desired. We present two such heuristics, both of which utilize an efficient method for computing a locally optimal tree with a given topology. The first systematically inserts Steiner points between edges of the minimal spanning tree meeting at angles less than 120 degrees, performing a local optimization at the end. The second begins by finding the Steiner tree for three of the fixed points. Then, at each iteration, it introduces a new fixed point to the tree, connecting it to each possible edge by inserting a Steiner point, and minimizes over all connections, performing a local optimization for each. We present a variety of test cases that demonstrate the strengths and weaknesses of both algorithms. This revised version was published online in July 2006 with corrections to the Cover Date.     

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On the determination of the column dead volume from homologous series

Summary The calculation of the column dead volume from high precision gross retention times of the n-alkanes pentane to heptadecane in an ODS/MeOH system yields values showing an apparently linear decrease with increasing carbon number. This effect is thought to be related to the partial exclusion from pores. If retention data are corrected for exclusion, one uniform dead volume is obtained.