Surface Deformation due to Shear and Ploughing in a Halfspace

Sheet and bulk metal forming are widely used manufacturing methods. The interaction between worktool and workpiece in such a process causes friction which has a remarkable impact on the expended energy of the process. Therefore the influence of friction is important. Friction can be split into shearing and ploughing [1]. Ploughing is the plastic deformation of a soft surface by a hard contact partner. Shear forces are only transferred in the real contact area where material contact occurs. The investigation of the contribution of both ploughing and shearing to the total friction resistance is done with the use of an elasto-plastic halfspace model. The multiscale character of surfaces demands a fine discretization, which results in numerical effort. While a finite element method takes into account both surface and bulk of the contact partners, the halfspace model only regards the contact surfaces and thereby consumes less computing capacity. In order to identify the friction resistance, two rough surfaces get into contact. After full application of the normal load, the surfaces are moved relatively to each other. New asperities of the contact surfaces get into contact and are plastically deformed. These deformations are used to estimate the ploughing effect in dependency on the relative displacement. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Identification of the lamination stack's behavior simulated with a multi-scale homogenization using a progressive contact formulation

The influence of the lamination stack on the mechanical behavior of an electrical motor is significant, especially for lightweight designs. Information about the stack's behavior is relevant for a proper calculation of the whole motor. This behavior is dependent on the contact between the single sheets resulting from the roughness and the behavior of the roughness peaks. The normal behavior is an elasto-plastic and progressive one, which results mainly of the number of roughness peaks in contact. Whereas the tangential micro-slip behavior is dependent on the single contacts and the friction coefficient. Both behaviors can be described by models and thus it is possible to calculate the behavior of a whole stack using an homogenization based on representative volume elements. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Littlewood-Richardson rule for wreath products with symmetric groups and the quiver of the category F≀FIn

We give a new proof for the Littlewood-Richardson rule for the wreath product F?S_n where F is a finite group. Our proof does not use symmetric functions but use more elementary representation theoretic tools. We also derive a branching rule for inducing the natural embedding of F?S_n to F?S_n+1. We then apply the generalized Littlewood-Richardson rule for computing the ordinary quiver of the category F?FI_n where FI_n is the category of all injective functions between subsets of an n-element set.     

Industrielle und natürliche Kernreaktoren

As described in the preceding article, all elements with atomic masses above that of iron and also the radioactive elements thorium and uranium have been formed by a supernova star explosion. Their long‐lived isotopes of thorium and uranium are now distributed in the earth crust. The chemistry of uranium and thorium is of less importance, but these elements can be used to produce enormous amounts of energy in nuclear power stations. It will be described how it works. Surprisingly, small natural nuclear reactors were producing heat during hundreds of thousand years. Subsequently, we are dealing with this phenomenon, the principle of nuclear fission, the different types of nuclear reactors, security aspects and new developments.     

Elusive O═P≡N, a rare example of phosphorus σ2λ5-coordination

Two linear isomers, OPN and ONP, were formed in an Ar matrix at 16 K by ArF laser (λ = 193 nm) photolysis of phosphoryl triazide, OP(N(3))(3), and comprehensively characterized by their mid- and far-IR spectra as well as (14/15)N isotopic data. Two intermediates, (N(3))(2)P(O)N and N(3)P(O)N(4), have been isolated in an Ar matrix and spectroscopically characterized. Photolysis of these intermediates using near-UV/vis light (λ > 320 nm) was shown to yield exclusively ONP, which under ArF laser irradiation selectively photo-isomerized to OPN. The photochemical and molecular properties of OPN and ONP are discussed on the basis of experimental and ab initio calculated results.     

Amplified analysis of DNA by the autonomous assembly of polymers consisting of DNAzyme wires

A systematic study of the amplified optical detection of DNA by Mg(2+)-dependent DNAzyme subunits is described. The use of two DNAzyme subunits and the respective fluorophore/quencher-modified substrate allows the detection of the target DNA with a sensitivity corresponding to 1 × 10(-9) M. The use of two functional hairpin structures that include the DNAzyme subunits in a caged, inactive configuration leads, in the presence of the target DNA, to the opening of one of the hairpins and to the activation of an autonomous cross-opening process of the two hairpins, which affords polymer DNA wires consisting of the Mg(2+)-dependent DNAzyme subunits. This amplification paradigm leads to the analysis of the target DNA with a sensitivity corresponding to 1 × 10(-14) M. The amplification mixture composed of the two hairpins can be implemented as a versatile sensing platform for analyzing any gene in the presence of the appropriate hairpin probe. This is exemplified with the detection of the BRCA1 oncogene.     

Synthesis and characterization of sulfuryl diazide, O2S(N3)2

Sulfuryl diazide, O(2)S(N(3))(2), previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 °C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C(2)) conformer to be 6.6 kJ mol(-1) lower in energy than the syn (C(s)) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO(2)N(3), has also been prepared and characterized by IR and Raman spectroscopy.