A simple radiochemical determination of90Sr in environmental samples

A simple procedure for the determination of⁹⁰Sr in environmental samples is described. The method uses the different solubilities of the oxalates of calcium and strontium in presence of a large excess of calcium. For this reason the method is especially suited for Ca-rich samples, as e.g., bones or soils. However, after addition of supplementary calcium it works equally well for other types of samples. The method was tested by analyzing the IAEA Certified Reference Materials soil, animal bone and algae.     

Chiral close-packing of achiral star-shaped molecules on solid surfaces

From the interplay of scanning tunneling microscopy and theoretical calculations, we study the chiral self-assembly of achiral HtB-HBC molecules upon adsorption on the Cu(110) surface. We find that chirality is expressed at two different levels: a +/-5 degrees rotation of the molecular axis with respect to the close-packed direction of the Cu(110) substrate and a chiral close-packed arrangement expected for star-shaped molecules in 2D. Out of the four possible chiral expressions, only two are found to exist due the effect of van der Waals (vdW) interactions forcing the molecules to simultaneously adjust to the atomic template of the substrate geometry and self-assemble in a close-packed geometry.     

Deformations and derived categories

We generalize the deformation theory of representations of profinite groups developed by Mazur and Schlessinger to complexes of modules for such groups. As an example, we determine the universal deformation ring of the compact étale hypercohomology of μ_p on certain affine CM elliptic curves studied by Boston and Ullom. To cite this article: F.M. Bleher, T. Chinburg, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 97–100     

Towards environmentally friendly, dry deposited, water developable molecular glass photoresists

Photoresists based on molecular glasses are gaining more and more importance as resist material to replace polymer based photoresist. In addition environmental issues have to be considered in the long-term. Therefore the paper describes novel negative photoresists containing a ternary mixture of a glassy low molecular functional polyphenol where the film preparation is possible by solvent-free physical vapor deposition. After UV light exposure and a thermal annealing process to enable acid catalyzed crosslinking between the molecular glass and the crosslinker, the photoresist was developed using only water to give well-defined patterns. In order to experimentally study efficiently the multiple parameters such as composition, exposure dose, and development times combinatorial PVD techniques were utilized.     

Catching proteins in liquid helium droplets

An experimental approach is presented that allows for the incorporation of large mass-to-charge ratio selected ions in liquid helium droplets. It is demonstrated that droplets can be efficiently doped with a mass-to-charge ratio selected amino acid as well as with the much bigger m ≈ 12,000 amu protein cytochrome C in selected charge states. The sizes of the ion-doped droplets are determined via electrostatic deflection. Under the experimental conditions employed, the observed droplet sizes are very large and range, depending on the incorporated ion, from 101? helium atoms for protonated phenylalanine to 1012 helium atoms for cytochrome C. As a possible explanation, a simple model based on the size and internal energy dependence of the pickup efficiency is given.     

Universal Deformation Rings for the Symmetric Group <Emphasis Type="Italic">S</Emphasis><Subscript>4</Subscript>

Let k be an algebraically closed field of characteristic 2, and let W be the ring of infinite Witt vectors over k. Let S ₄ denote the symmetric group on 4 letters. We determine the universal deformation ring R(S ₄,V) for every kS ₄-module V which has stable endomorphism ring k and show that R(S ₄,V) is isomorphic to either k, or W[t]/(t ²,2t), or the group ring W[ℤ/2]. This gives a positive answer in this case to a question raised by the first author and Chinburg whether the universal deformation ring of a representation of a finite group with stable endomorphism ring k is always isomorphic to a subquotient ring of the group ring over W of a defect group of the modular block associated to the representation.     

Universal deformation rings and dihedral 2-groups

Let k be an algebraically closed field of characteristic 2,and let W be the ring of infinite Witt vectors over k. Supposethat D is a dihedral 2-group. We prove that the universal deformationring R(D, V) of an endo-trivial kD-module V is always isomorphicto W [/2x/2]. As a consequence, we obtain a similar result formodules V with stable endomorphism ring k belonging to an arbitrarynilpotent block with defect group D. This confirms, for suchV, conjectures on the ring structure of the universal deformationring of V that had previously been shown for V belonging tocyclic blocks or to blocks with Klein four defect groups.     

Multilevel algorithms for finite difference discretizations on sparse grids

We propose some algorithms to solve the system of linear equations arising from the finite difference discretization on sparse grids. For this, we will use the multilevel structure of the sparse grid space or its full grid subspaces, respectively.