Formation of a new Ia-3d cubic meso-structured silica via triblock copolymer-assisted synthesis

A new mesoporous silica structure with cubic Iad symmetry has been synthesized. The structure has very large unit cell dimensions, up to 250 A in the as-synthesized form and 222 A after calcination, and the surface area is around 700 m2/g. The syntheses were done according to well-established synthesis conditions with the triblock copolymers Pluronics P103 or P123, except for the addition of NaI to the synthesis mixture. Small-angle X-ray scattering revealed that the sample has Iad symmetry. According to electron micrographs, the structure is similar to that of MCM-48, and we thus propose that the structure lies on the gyroid minimal surface.     

Synthesis and structure‐activity relationship of several aromatic ketone‐based two‐photon initiators

Several novel aromatic ketone‐based two‐photon initiators containing triple bonds and dialkylamino groups were synthesized and the structure‐activity relationships were evaluated. Branched alkyl chains were used at the terminal donor groups to improve the solubility in the multifunctional monomers. Because of the long conjugation length and good coplanarity, the evaluated initiators showed large two‐photon cross section values, while their fluorescence lifetimes and quantum yields strongly depend on the solvent polarity. All novel initiators exhibited high activity in terms of two‐photon‐induced microfabrication. This is especially true for fluorenone‐based derivatives, which displayed much broader processing windows than well‐known highly active initiators from the literature and commercially available initiators. While the new photoinitiators gave high reactivity in two‐photon‐induced photopolymerization at concentration as low as 0.1% wt, these compounds are surprisingly stable under one photon condition and nearly no photo initiation activity was found in classical photo DSC experiment. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Deformation effects in the12C-12C system

The quantized adiabatic time dependent Hartree-Fock (quantized ATDHF) theory is applied to the¹²C-¹²C-system. Especially the intrinsic oblate ground state deformation of this nucleus is considered. For four relevant mutual orientations of the two nuclei the optimal, i.e. maximally decoupled collective paths, associated to relative motion, are evaluated by solving a coupled set of nonlinear differential equations on three dimensional grids in coordinate and momentum space. In a second step, the constituents of the corresponding collective Hamiltonian are calculated. Besides the collective potentials this includes the evaluation of the appropriate mass parameters, of the quantum corrections with regard to rotation, translation and collective relative motion and of the centrifugal potentials, all of which are shown to be important. By means of generalized WKB methods, subbarrier fusion cross sections are evaluated for different assumptions on the reaction process and compared with experimental data. Finally, the collective Hamiltonian is calculated for a head-on-collision of two¹²C-chains.     

A New Supramolecular Assembly Formed by Melamine and Sulfuric Acid

Polymeric melaminium sulfate [(LH₂)₂(SO₄)₂]_n has been synthesized by reaction of melamine L with sulfuric acid in aqueous solution. The compound was characterized by elemental analysis, ¹H NMR, ESI MS and a single crystal X‐ray diffraction analysis. The architecture of the assembly formed is based on hydrogen bonded dimers of diprotonated melaminium cations (LH₂)²⁺ which are linked by a hydrogen bonded network with sulfate ions forming 2D sheets. A 3D polymeric structure results from the presence of mutual hydrogen bonds between sulfate ions and melaminium cations in different sheets. Significant π‐π stacking is also present between the aromatic cations in this supramolecular arrangement.     

The MAMI C accelerator

The demand for CW electron beam energies of more than 1?GeV led to the decision of constructing a worldwide unique accelerator – the Harmonic Double-Sided Microtron (HDSM). This machine nearly doubles the beam energy of the Mainz Microtron cascade from up to 855?MeV to now 1.6?GeV to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. For the recent decade the construction and commissioning of the HDSM at the Institut für Kernphysik has been the major task of the accelerator department.     

The theory of lock-on transitions in modulated structures

Various approaches to the theory of lock-on transitions are reviewed and related to one another. Some specific examples are then discussed.