Direct extraction of the Eliashberg function for electron-phonon coupling: a case study of Be(10(-)10)

We propose a systematic procedure to directly extract the Eliashberg function for electron-phonon coupling from high-resolution angle-resolved photoemission measurement. The procedure is successfully applied to the Be(10(-)10) surface, providing new insights into electron-phonon coupling at this surface. The method is shown to be robust against imperfections in experimental data and suitable for wider applications.     

Polyesters by a Radical Pathway: Rationalization of the Cyclic Ketene Acetal Efficiency

Radical ring‐opening polymerization (rROP) of cyclic ketene acetals (CKAs) combines the advantages of both ring‐opening polymerization and radical polymerization thereby allowing the robust production of polyesters coupled with the mild polymerization conditions of a radical process. rROP was recently rejuvenated by the possibility to copolymerize CKAs with classic vinyl monomers leading to the insertion of cleavable functionality into a vinyl‐based copolymer backbone and thus imparting (bio)degradability. Such materials are suitable for a large scope of applications, particularly within the biomedical field. The competition between the ring‐opening and ring‐retaining propagation routes is a major complication in the development of efficient CKA monomers, ultimately leading to the use of only four monomers that are known to completely ring‐open under all experimental conditions. In this article we investigate the radical ring‐opening polymerization of model CKA monomers and demonstrate by the combination of DFT calculations and kinetic modeling using PREDICI software that we are now able to predict in silico the ring‐opening ability of CKA monomers.     

The Stereoselective Aldol Condensation of α-Fluoroacetates

2,6-Di-t-butyl-4-methylphenyl(BHT) and benzyl α-fluoroacetates were converted to their lithium enolates and were utilized in the aldol condensation. The improved diastereoselectivity found with the BHT esters is thought to arise from of equilibration of the aldol product rather than stereoselective enolate formation.     

Surfaces: a playground for physics with broken symmetry in reduced dimensionality

With our crystal ball in front of us, we attempt to articulate the opportunities and challenges for a surface physicist in the beginning of the new millennium. The challenge is quite clear: to use the unique environment of a surface or interface to do fascinating physics, while taking full advantage of the skills the community has developed over the last 30 years. The opportunities appear to be endless! In this age of Nanotechnology where the promise is to shape the world atom by atom, leading to the next industrial revolution [Nanotechnology: shaping the world atom by atom, National Science and Technology Council, Committee on Technology, 1999], surface science should be at the very forefront of both technological and scientific advances. The smaller objects become, the more important their surfaces become. In this article we focus on the role of a surface physicist in the emergence of nanoscale collective phenomena in complex materials.     

A study of mechanical homogeneity in as-cast bulk metallic glass by nanoindentation

A surface softening effect induced during copper-mould suction casting of bulk metallic glass is investigated as a function of rod diameter and glass fragility index, m, by nanoindentation. A reduction in hardness and reduced modulus at the rod surface is found to be favoured in small diameter castings and in fragile systems, respectively resulting from limited in-situ annealing and from a greater diversity of metastable atomic environments in the potential energy landscape of fragile glasses. Enhanced propensity for shear transformation zone nucleation in the low moduli surface is explained in terms of reduced atomic connectivity arising from a reduction in local co-ordination number and a lowering of the shear modulus. Finally, the structure and mechanical diversity that is possible in as-cast bulk metallic glass rods is explored through a relative quantification of shear modulus and plastic zone size across the whole as-cast state and in a single rod. These findings illustrate the sensitivity of bulk metallic glass to preparation, especially in respect of thermal history, potentially making replication of mechanical data between researchers problematic.     

Crazing in semicrystalline thermoplastics

The deformation processes in crystalline polymers have been studie ever since the discovery of chain folding in 1957. Since then, scientists have been intrigued by the different steps of the transformation of the folded-chain lamellar structure of single crystals or of macroscopically isotropic, often spherulitic, polymers into fibrous morphologies (see Refs. 1 and 2 for early reviews). The importance of molecular tilt, of inter- and intralamellar slip, and of micronecking were rapidly recognized [1–4]. In this paper, we discuss the analogies and differences with respect to crazing of glassy amorphous polymers. Obviously, there is an extensive body of literature on the micromechanics of crazing (see the reviews in Refs. 5–9). On the basis of these studies, it has been established that crazes in amorphous polymers are well-defined regions with approximately planar boundaries that extend perpendicular to the direction of maximum principal tensile stress and that contain highly stretched and voided material [7]. However, crazelike features have also been observed in many semicrystalline polymers (polyethylene [PE], isotactic polypropylene [IPP], isotatic polystyrene [IPS], polyoxymethylene [POM], polyamide 6 and 66 [PA6 and PA66], polycarbonate [PC], polyethylene terephthalate [PET], polybutylene terephthalate [PBT], polyvinylidene fluoride [PVDF], and polyether ether ketone [PEEK]). They are designated in the literature [3–10] as micronecks, true crazes, fibrillar deformation zones (DZs), or simply as crazes since they correspond well to the above definition.     

Bounding the Size of Equimatchable Graphs of Fixed Genus

A graph G is said to be equimatchable if every matching in G extends to (i.e., is a subset of) a maximum matching in G. In an earlier paper with Saito, the authors showed that there are only a finite number of 3-connected equimatchable planar graphs. In the present paper, this result is extended by showing that in a surface of any fixed genus (orientable or non-orientable), there are only a finite number of 3-connected equimatchable graphs having a minimal embedding of representativity at least three. (In fact, if the graphs considered are non-bipartite, the representativity three hypothesis may be dropped.) The proof makes use of the Gallai-Edmonds decomposition theorem for matchings.