Calabi-Yau 4-folds and toric fibrations

We present a general scheme for identifying fibrations in the framework of toric geometry and provide a large list of weights for Calabi-Yau 4-folds. We find 914 164 weights with degree d ≤ 150 whose maximal Newton polyhedra are reflexive and 525 572 weights with degree d ≤ 4000 that give rise to weighted projective spaces such that the polynomial defining a hypersurface of trivial canonical class is transversal. We compute all Hodge numbers, using Batyrev's formulas (derived by toric methods) for the first and Vafa's formulas (obtained by counting of Ramond ground states in N = 2 LG models) for the latter class, checking their consistency for the 109 308 weights in the overlap. Fibrations of k-folds, including the elliptic case, manifest themselves in the N lattice in the following simple way: The polyhedron corresponding to the fiber is a subpolyhedron of that corresponding to the k-fold, whereas the fan determining the base is a linear projection of the fan corresponding to the k-fold.     

Low energy antiproton-proton annihilation and meson spectroscopy

Recent results in antiproton-proton annihilation at rest from the Crystal Barrel at CERN/LEAR are reviewed. Rates for annihilation at rest into various two-body channels have been measured. In spite of the complexity of the annihilation mechanism, simple tests based on the underlying quark constituents can be applied. The annihilation process is also useful to investigate the spectrum of light quark mesons and to search for exotic (non-q¯q) mesons. Three scalar states have been found in the 1500 MeV mass region. One of them is a good candidate for the ground state glueball.     

Lithium intercalation into disordered carbon/SiCN composite. Part 2: Raman spectroscopy and <Superscript>7</Superscript>Li MAS NMR investigation of lithium storage sites

Within this work, we analyze the lithium storage sites within carbon/silicon carbonitride (SiCN) composites. Commercial carbons, HD3 (hard carbon) and LD1N and LD2N (soft carbons), of varying porosity are impregnated with polysilazane (HTT 1800) and pyrolysed at 1100 °C. It is found in the first part of this study (Graczyk-Zajac et al. J Solid State Electrochem 19:2763–2769, 2015) that the initial porosity of the carbon phase plays an important role in determining the lithium insertion capacity and rate capability of the composite material. By applying Raman spectroscopy and solid-state ⁷Li MAS NMR on pristine, lithiated, and delithiated samples, we investigate the lithium storage sites within the composite materials. By means of Raman spectroscopy, it has been found that lithium storage in hard carbon-derived composites occurs in a significant extent via adsorption-like process within unorganized carbon, whereas for the soft carbon composites, storage in turbostratic carbon is identified. ⁷Li solid-state NMR confirms these findings revealing that more than 33 % of lithium stored in HD3/SiCN is adsorbed in ionic form at the surface and in pores of the composite, while around 38 % is stored between carbon layers. LD1N and LD2N composites store more than 50 % of lithium in the intercalation-type sites.     

On the performance of the Prange-Hellinger-Reissner finite element formulation for elasto-plasticity at small strains

This contribution deals with a stress-displacement mixed finite element formulation for elasto-plasticity within the framework of small deformations based on the Prange-Hellinger-Reissner (PHR) functional. The interpolations for the displacements are given by standard Lagrangian shape functions and a 5-parameter discontinuous interpolation is introduced for the stresses which was published by [1]. Based on the principle of maximum plastic dissipation the flow rule and hardening law will be derived by regarding a von Mises yield criterion, see [2]. In contrast to [3], we apply a point-wise enforcement of the flow rule, hardening law and loading/unloading conditions. This work is related to the physically nonlinear mixed finite element based on the Prange-Hellinger-Reissner formulations for elasto-plasticity, [4]. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Making and breaking peptide bonds: protein engineering using sortase

Sortases are a class of bacterial enzymes that possess transpeptidase activity. It is their ability to site-specifically break a peptide bond and then reform a new bond with an incoming nucleophile that makes sortase an attractive tool for protein engineering. This technique has been adopted for a range of applications, from chemistry-based to cell biology and technology. In this Minireview we provide a brief overview of the biology of sortase enzymes and current applications in protein engineering. We identify areas that lend themselves to further innovation and that suggest new applications.     

A systematic approach to reliably characterize soils based on Bevameter testing

Although a lot of information about soil parameter identification exists in literature, there is currently no algorithm who makes use both of state of the art identification methodologies and incorporating statistical analysis. In this paper a state of the art soil parameter identification method is presented including the calculation of its standard deviations and a proper weighting of the objective function. With this algorithm and a Bevameter with advanced sensor and actuator technology a test campaign is started to find a reliable soil preparation, which is applicable to a large planetary rover performance testbed. Furthermore, the preparation method has to be valid and stable for various types of dry, granular and frictional soils, typically used for planetary rover testing in space robotics, since the result of pre-tests show that the soil parameters are highly depending on the preparation. Besides preparation, the soil parameters are also influenced by different Bevameter test setup variables. Thus, the effect of the penetration velocity as well as the penetration tool geometry for pressure–sinkage tests on soil parameters is investigated. For shear tests the influence of the dimension of the shear ring is analysed as well as the variation of the grouser height, the number of the grousers and the increase of the rotational shear velocity. The results of the extensive test campaign are evaluated by the proposed identification algorithms.