Altered thermodynamic and kinetic properties of MgH(2) infiltrated in microporous scaffold

MgH(2) nanoparticles with a size of <3 nm were formed by direct hydrogenation of Bu(2)Mg inside the pores of a carbon scaffold. The activation energy for the dehydrogenation was lowered by 52 kJ mol(-1) compared to the bulk material, and a significantly reduced reaction enthalpy of 63.8 ± 0.5 kJ mol(-1) and entropy (117.2 ± 0.8 J mol(-1)) was found for the nanoconfined system.     

Centrifugal microfluidic system for primary amplification and secondary real-time PCR

Pre-amplification is a basis for numerous polymerase chain reaction (PCR) protocols but bears severe contamination risks due to handling of high-copy DNA samples. Therefore we developed a self-contained centrifugal microfluidic system comprising pre-stored reagents; it enables pre-amplification of specific DNA sequences prior to automated aliquoting and real-time PCR in a modified commercial thermocycler.     

Crystal structure prediction using the minima hopping method

A structure prediction method is presented based on the minima hopping method. To escape local minima, moves on the configurational enthalpy surface are performed by variable cell shape molecular dynamics. To optimize the escape steps the initial atomic and cell velocities are aligned to low curvature directions of the current local minimum. The method is applied to both silicon crystals and well-studied binary Lennard-Jones mixtures. For the latter new putative ground state structures are presented. It is shown that a high success rate is achieved and a reliable prediction of unknown ground state structures is possible.     

Discretized fast–slow systems near pitchfork singularities

ABSTRACT

Motivated by the normal form of a fast–slow ordinary differential equation exhibiting a pitchfork singularity we consider the discrete-time dynamical system that is obtained by an application of the explicit Euler method. Tracking trajectories in the vicinity of the singularity we show, how the slow manifold extends beyond the singular point and give an estimate on the contraction rate of a transition mapping. The proof relies on the blow-up method suitably adapted to the discrete setting where precise estimates for a cubic map in the central rescaling chart make a key technical contribution.     

On predictions from spontaneously broken flavor symmetries

We discuss the predictive power of supersymmetric models with flavor symmetries, focusing on the lepton sector of the standard model. In particular, we comment on schemes in which, after certain ‘flavons’ acquire their vacuum expectation values (VEVs), the charged lepton Yukawa couplings and the neutrino mass matrix appear to have certain residual symmetries. In most analyses, only corrections to the holomorphic superpotential from higher-dimensional operators are considered (for instance, in order to generate a realistic _θ13${\theta }_{13}$ mixing angle). In general, however, the flavon VEVs also modify the Kähler potential and, therefore, the model predictions. We show that these corrections to the naive results can be sizable. Furthermore, we present simple analytic formulae that allow us to understand the impact of these corrections on the predictions for the masses and mixing parameters.     

Continuous time trading of a small investor in a limit order market

We provide a mathematical framework to model continuous time trading of a small investor in limit order markets. We show how elementary strategies can be extended in a suitable way to general continuous time strategies containing orders with infinitely many different limit prices. The general limit buy order strategies are predictable processes with values in the set of nonincreasing demand functions. It turns out that our strategy set of limit and market orders is closed, but limit orders can turn into market orders when passing to the limit, and any element can be approximated by a sequence of elementary strategies.     

Wavelength Orthogonal Photodynamic Networks

The ability of light to remotely control the properties of soft matter materials in a dynamic fashion has fascinated material scientists and photochemists for decades. However, only recently has our ability to map photochemical reactivity in a finely wavelength resolved fashion allowed for different colors of light to independently control the material properties of polymer networks with high precision, driven by monochromatic irradiation enabling orthogonal reaction control. The current concept article highlights the progress in visible light-induced photochemistry and explores how it has enabled the design of polymer networks with dynamically adjustable properties. We will explore current applications ranging from dynamic hydrogel design to the light-driven adaptation of 3D printed structures on the macro- and micro-scale. While the alternation of mechanical properties via remote control is largely reality for soft matter materials, we herein propose the next frontiers for adaptive properties, including remote switching between conductive and non-conductive properties, hydrophobic and hydrophilic surfaces, fluorescent or non-fluorescent, and cell adhesive vs. cell repellent properties.     

Molecular Mechanism of Action of the Antibiotic Rifampicin

The lipophilic antibiotic rifampicin is successfully used in the treatment of tuberculosis. On the molecular level it interferes with the metabolism of Eubacteria by blocking RNA synthesis. This effect is the consequence of the tight binding of the drug to a single and highly specific binding site on the DNA-dependent RNA polymerase. The enzyme-bound drug strongly inhibits RNA chain initiation and chain elongation. This inhibition can be explained by the influence of enzyme-bound rifampicin on binding sites for the reaction products diphosphate and RNA. In order to reach its target the antibiotic must penetrate into the cytoplasm of the bacteria. Mutants have been discovered which are resistant to rifampicin because its uptake from the medium is significantly reduced. The gene responsible for this effect has been cloned. It confers on bacterial cells with highly sensitive RNA polymerases a remarkable resistance to the drug.