Experimental-based material parameter identification of oocytes

In comparison to other eukaryotic cells, mammalian oocytes are characterised by a relative high diameter allowing in turn a straightforward micromechanical testing to study their mechanical properties. The structure of mammalian oocytes is characterised by the so-called zona pellucida (ZP), a thick glycoprotein layer, surrounding the cells interior, the ooplasm. In contrast to other cells, where the load is mainly carried by inner cell structures, in case of oocytes a huge amount of external loads is carried by the ZP. Aim of this work is the determination of the mechanical properties of oocytes. Therefore, a micromechanical setup has been developed and installed on a microscope. Beside the determination of the force-strain relation during loading, the deformation of the oocytes has been recorded optically, too. Both, the force-strain curves and the optical recordings build the basis for a proper parameter identification technique based on the inverse finite element method. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Port-Hamiltonian representation for pdes with second-order derivatives in the energy density

In this contribution we consider a port-Hamiltonian setting for partial differential equations. A crucial property of this system class is the property to be able to link a power balance relation to the structure of the equations. However, one has to take into account also the effects of energy flows via the boundary. This is straightforward when the Hamiltonian depends on derivative variables of first order, e.g. by using integration by parts. If second-order derivatives appear then integration by parts cannot be used without due care, thus we suggest an approach by using the so-called Cartan-form. We visualize the derivation of a power balance relation by using the Kirchhoff plate as an example. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Non-quadratic defect energy: A comparison of gradient plasticity simulations to discrete dislocation dynamics results

A small-deformation strain gradient plasticity (GP) model for single-crystals has been proposed in [1], including a grain boundary (GB) yield condition without hardening. It has been extended by a hardening term for the GBs after a comparison to discrete dislocation dynamics (DDD) results in [2]. Differences between the strain gradients of the GP results and the DDD results motivate the consideration of a non-quadratic defect energy [3] in the GP model. It is shown that the gradients in the GP model can be improved using an exponent different from two. Remaining discrepancies in the strain profiles, compared to the DDD results, are attributed to the neglect of the individual gradients of plastic slip and due to the lack of a mechanism for the misorientation-dependent elastic interactions of dislocations across GBs [4] in the GP model. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and Crystal Structure of LiY(CN2)2, Having a Structure Related to That of NiAs

The new ternary carbodiimide LiY(CN₂)₂ was synthesized by solid state metathesis reaction between YF₃ and Li₂(CN₂) in a silica tube at 550 °C. The X‐ray single‐crystal structure determination yielded an orthorhombic crystal system (Pbcn, Z = 4, a = 982.0(3), b = 698.5(2), c = 613.4(2) pm). The crystal structure can be considered related to the NiAs structure. The carbodiimide ions are arranged in layers following the motif of a hexagonal closest packing of sticks. Lithium and yttrium cations occupy all octahedral voids in an ordered fashion, alternating on top of each other along the hcp stacking direction.     

Transparent conducting Sn:ZnO films deposited from nanoparticles

Homogeneous transparent conducting Sn:ZnO films on fused silica substrates were prepared by dip-coating from nanoparticle dispersions, while the nanocrystalline Sn:ZnO particles with different dopant concentrations were synthesized by microwave-assisted non-aqueous sol–gel process using Sn(IV) tert-butoxide and Zn(II) acetate as precursors and benzyl alcohol as solvent. The dopant concentration had a great impact on the electrical properties of the films. A minimum resistivity of 20.3 Ω cm was obtained for a porous Sn:ZnO film with initial Sn concentration of 7.5 mol% after annealing in air and post-annealing in N₂ at 600 °C. The resistivity of this porous film could further be reduced to 2.6 and 0.6 Ω cm after densified in Sn:ZnO and Al:ZnO reaction solution, respectively. The average optical transmittance of a 400-nm-thick Sn:ZnO film densified with Sn:ZnO after the two annealing steps was 91%.     

Robust Design using classical optimization

The complexity of technical products increases significantly, due to an increasing number of interacting design variables of many components and subsystems. At the same time, the need for separated development processes is increasing due to specialization and outsourcing. Solution space methods are designed to solve this conflict. The requirements from an upper level, e.g. performance measures of the whole system, can be cascaded down to requirements on a lower level, e.g. performance measures of the subsystems or components, as it is done in the V-model approach. The method does not only take the numerous interactions into account but also guarantees the resulting intervals of different parameters to be independent of each other. Unfortunately, the computational cost of the state-of-the-art stochastic approach is high. The approach in this paper shows that the computational effort can be reduced considerably using a gradient based optimization approach for constraint problems. We demonstrate that the approach reduces the required number of function evaluations for a chassis design problem by a factor of 30, but more important, the CPU time for solving the problem by a factor of 20. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

What is a protein crystal? Can we apply the terminology of classical industrial crystallization to them?

The nature of protein crystals is discussed. Since protein crystals contain not only proteins but also other substances the usage of conventional terms (of industrial crystallization) of naming such crystals is questioned. The proof that there are other components than the protein itself in a protein crystal is given. It is suggested to use a procedure like in biotechnology to guarantee the production of the right protein crystals according to the PAT concept. It is suggested not to use other established names like “hydrates”, “solvates”, “but crystals for proteins since the definitions do not fit the nature of the protein crystals.