The lonely runner problem for lacunary sequences

The paper contains a new proof with a small improvement of a theorem of A. Dubickas on The Lonely Runner Conjecture and lacunary sequences. The proof is an adaptation of the Bernshteyn’s proof of the Lopsided Local lemma from his Local Cut Lemma (Bernshteyn, 2017).     

Probing o‐Diphenylphosphanyl Benzoate (o‐DPPB)‐Directed CC Bond Formation: Total Synthesis of Dictyostatin

Herein, we report a robust total synthesis of dictyostatin. This polyketide natural product has attracted much attention because of its impressive antiproliferative activity against several human cancer‐cell lines. We accomplished its synthesis in a highly convergent manner from three fragments of equal complexity, which were prepared on multigram scale. The southern and northwestern subunits were constructed through application of our o‐DPPB‐directed hydroformylation and allylic substitution methodology, respectively. These methods generated the C6 and C14 stereocenters of dictyostatin with good diastereoselectivities and simultaneously allowed further elaboration of the fragments by Wittig olefination and Sharpless asymmetric epoxidation, respectively. The compelling performance of the hydroformylation and allylic substitution with regard to practicability, selectivity, and scale underline their value for the construction of propionate motifs.     

Mean value and volume-based sensitivity analysis for Olympic rankings

This article describes two methods of creating Olympic rankings based on number of medals won. One method is based on the weighted mean value, which we will show is equivalent to the compromise programming known in Multi-Criteria Decision Analysis (MCDM). The other method uses volume-based sensitivity analysis. Both methods presented in this paper can also be used to construct rankings that include more than just the three top positions.     

Particulate and continuum mechanics of microgel pastes: effect and non-effect of compositional heterogeneity

Microgels are deformable colloids that can be packed by external compression; such packing transforms a suspension of loose microgels into a viscoelastic paste with mechanical properties controlled by the elasticity of the constituent particles. We aim to understand how the presence of microgel particles with different individual elastic moduli affects this interplay in heterogeneous microgel packings. We do this by preparing microgel pastes that contain both soft, loosely cross-linked and stiff, densely cross-linked microgel particles and probe their shear elasticity. We consider particle packing fractions that cover the range from particles at the onset of contact to particles that are strongly packed, deformed, and deswollen to investigate the transition from a particulate suspension to a macrogel-type system. These studies reveal that the elasticity of heterogeneous microgel suspensions at low packing is due to the response of the soft, easily deformable microgel particles alone, whereas at high packing both soft and stiff microgels linearly add to the paste elasticity. This fundamental difference is due to the fundamentally different origin of elasticity at different microgel packing; whereas the soft particle interaction potential dominates the suspension mechanics at low microgel packing, rubber-like elasticity that equally reflects both soft and stiff contributions governs the mechanics of the same samples at high microgel packing.     

Sensitive microgels as model colloids and microcapsules

Polymer microgels consist of swollen networks of crosslinked macromolecules with particulate dimensions. If these networks exhibit a delicate interplay with their environment that allows them to be swollen and deswollen or to be crosslinked and decrosslinked upon external stimulation, they can serve for a variety of applications in sensing and actuation. Such environmental sensitivity can be realized either by the use of covalently crosslinked polymer networks that exhibit critical miscibility with their swelling medium or by the use of transient and reversible, supramolecular chain crosslinking. This article highlights some achievements in the synthesis and application of sensitive microgels. In one area of focus, the article discusses the use of sensitive microgels as model colloids to study relations between structure, dynamics, and properties of soft matter. In another area of focus, the paper discusses the use of these microgels to encapsulate, host, and release functional additives. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 435–449     

Experimental and Numerical Study of Polypropylene/Polyethylene Thin Foil in Biaxial Tension

The material under consideration is a thermoplastic copolymer blend of polypropylene and polyethylene (PP/PE), constituting the core layer of a steel/polymer/steel composite material. A biaxial loading machine was developed for studying the behavior of the copolymer subjected to in-plane complex stress states. A study on the shape of the specimen by means of numerical finite element simulations and preliminary experimental tests are carried out, in order to obtain a maximization of the strain distribution in the middle region of the cruciform specimen. Afterwards, the sensitivity of the mechanical response under both equibiaxial and non-equibiaxial conditions is addressed. All the experiments are monitored by means of a digital image correlation (DIC) system, providing full-field measurements of the displacements, and, consequently, of the strain distribution. The presented experimental results will be used for validating the material model developed for the PP/PE layer material. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimal adaptation of acoustic black holes by evolutionary optimization algorithms

The interest of engineers is focusing increasingly on a reduced sound radiation of constructions. In particular, structures with a large surface, such as cabin linings of airplanes as well as a roof or a bottom plate of cars, tend to be good acoustic radiators and lead to an annoyance of passengers. As countermeasures, often complex and time consuming design changes or expensive active measures are used. In many cases, a more elegant and cheaper option is to improve the acoustic properties by using passive measures. Acoustic black holes are an innovative passive method which combine two advantages: A material reduction by improving acoustic properties is performed. The main idea is to guide and to focus acoustically critical bending waves by a specific wall thickness diminution. Through targeted local damping placement in the middle of an acoustic black hole, a structure can be globally damped in a very efficient way. The efficiency depends on the position and size of the acoustic black holes [1]. Finding the optimal size and position on the structure is therefore an important challenge. This paper introduces a new strategy to find an optimal position of acoustic black holes to reduce the sound radiation of plane structures by using evolutionary optimization algorithms. Numerical calculations are exemplarily shown on a rectangular plate. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase equilibrium measurements of acoustically levitated squalane–CO2 mixtures by Raman spectroscopy

This work describes the phase equilibrium measurements of acoustically levitated binary mixtures with concentration measurements using Raman spectroscopy without sample extraction of the autoclave. The levitator design is implemented in a Single‐Droplet Optical Cell for levitation processes under varying atmospheres. The advantages of acoustic levitation of small droplets under increased temperatures and pressure combined with spectroscopic applications like Raman spectroscopy enable novel experiments possibly relevant to the fields of chemical engineering. To the author's knowledge, this is the first use of Raman spectroscopy for phase equilibria investigations on acoustically levitated droplets under high pressure and temperature. The results show very good agreements with literature data. Copyright © 2014 John Wiley & Sons, Ltd.