Vortex wake mitigation of an airfoil with winglets by active rudders

The wake vortex hazard and the required separation distances between aircraft at airports constitute an impediment to the growth of air traffic at major hubs. One approach to reduce separation distances is the exploitation of the inherent instability in vortex systems, leading to an accelerated breakdown. In this paper we show the impact of excitation by different control surfaces on the stability behavior of the wake of a rectangular wing with winglets. The experiment shows that the excitation through winglet rudders and ailerons yields the best results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Efficient parallel simulation of biphasic materials in biomechanics

Biphasic materials are widely used for the modelling and the numerical simulation of articular cartilage within joints. In combination with contact, the numerical solution of the arising discrete systems is a demanding task, in particular for realistic geometries. We consider the stability and efficiency of different multilevel approaches for the numerical solution of the resulting non–smooth systems. Moreover, multilevel methods are derived which allow for the efficient numerical simulation of biphasic materials in contact. Numerical examples on problem specific geometries in three space dimensions are given. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Macro modelling and homogenization for transformation induced plasticity of a low-alloy steel

Metal forming processes are important technologies for the production of engineering structures. In order to optimize the resulting material properties, it becomes necessary to simulate the entire forming process by taking into account physical effects such as phase transformations. In this work, we concentrate on the phase change from austenite to martensite and present a macroscopic material model, which combines the effect of classical plasticity with the effect of transformation induced plasticity (TRIP). An extensive experimental database for a low-alloy steel is used for parameter identification, thus taking into account the effects of uniaxial compressive and tensile stress on the kinetics of phase transformation at different temperatures. For temperatures below the martensite start temperature with simultaneous stresses above the yield limit, it is difficult to obtain experimental data. Consequently, a numerical homogenization technique is employed for this case. In a further part of this paper, an effective integration scheme is provided, which is implemented into a commercial finite element program. In a finite element simulation, the austenite to martensite phase transformation in a shaft subjected to thermal loading is investigated.     

Squalenyl Hydrogen Sulfate Nanoparticles for Simultaneous Delivery of Tobramycin and an Alkylquinolone Quorum Sensing Inhibitor Enable the Eradication of P. aeruginosa Biofilm Infections

Elimination of pulmonary Pseudomonas aeruginosa (PA) infections is challenging to accomplish with antibiotic therapies, mainly due to resistance mechanisms. Quorum sensing inhibitors (QSIs) interfering with biofilm formation can thus complement antibiotics. For simultaneous and improved delivery of both active agents to the infection sites, self-assembling nanoparticles of a newly synthesized squalenyl hydrogen sulfate (SqNPs) were prepared. These nanocarriers allowed for remarkably high loading capacities of hydrophilic antibiotic tobramycin (Tob) and a novel lipophilic QSI at 30 % and circa 10 %, respectively. The drug-loaded SqNPs showed improved biofilm penetration and enhanced efficacy in relevant biological barriers (mucin/human tracheal mucus, biofilm), leading to complete eradication of PA biofilms at circa 16-fold lower Tob concentration than Tob alone. This study offers a viable therapy optimization and invigorates the research and development of QSIs for clinical use.     

A Modular Synthesis of Teraryl‐Based α‐Helix Mimetics,Part 1: Synthesis of Core Fragments with Two Electronically Differentiated Leaving Groups

Teraryl‐based α‐helix mimetics have proven to be useful compounds for the inhibition of protein–protein interactions (PPI). We have developed a modular and flexible approach for the synthesis of teraryl‐based α‐helix mimetics. Central to our strategy is the use of a benzene core unit featuring two leaving groups of differentiated reactivity in the Pd‐catalyzed cross‐coupling used for terphenyl assembly. With the halogen/diazonium route and the halogen/triflate route, two strategies have successfully been established. The synthesis of core building blocks with aliphatic (Ala, Val, Leu, Ile), aromatic (Phe), polar (Cys, Lys), hydrophilic (Ser, Gln), and acidic (Glu) amino acid side chains are reported.