Lane formation in a system of dipolar microswimmers

Using Brownian Dynamics (BD) simulations we investigate the non-equilibrium structure formation of a two-dimensional (2D) binary system of dipolar colloids propelling in opposite directions. Despite of a pronounced tendency for chain formation, the system displays a transition towards a laned state reminiscent of lane formation in systems with isotropic repulsive interactions. However, the anisotropic dipolar interactions induce novel features: First, the lanes have themselves a complex internal structure characterized by chains or clusters. Second, laning occurs only in a window of interaction strengths. We interprete our findings by a phase separation process and simple force balance arguments

To Sing or Not to Sing: The Effect of Singing on Recall of Nursery Rhymes with Preschoolers

Much research has been cited which notes a positive regard for the incorporation of music and singing with young children. The study conducted here sought to examine which method of presentation of four selected nursery rhymes, singing or read-aloud, would promote greater recall efficacy with four year olds. The study included fifty-seven four year olds who participated in a two part study. The subjects were divided into two groups, Group A and Group B. For Part One of the study, Group A heard Rhymes One and Two through a read-aloud book experience and Group B heard the same rhymes through songs. After each group heard each rhyme a total of eight times over a one month period, each subject was asked to verbally recite each nursery rhyme to the examiner. Upon collection of all of the data necessary for Part One, Part Two of the study was begun. Part two was a replication of Part One but the method of presentation of two new nursery rhymes for each group was reversed. Five t-tests were used to analyze the data collected for this study. The results showed three instances in which read-aloud was a favored mode of presentation and two instances in which no significant difference was found

Generic model for tunable colloidal aggregation in multidirectional fields

Based on Brownian Dynamics computer simulations in two dimensions we investigate aggregation scenarios of colloidal particles with directional interactions induced by multiple external fields. To this end we propose a model which allows continuous change in the particle interactions from point-dipole-like to patchy-like (with four patches). We show that, as a result of this change, the non-equilibrium aggregation occurring at low densities and temperatures transforms from conventional diffusion-limited cluster aggregation (DLCA) to slippery DLCA involving rotating bonds; this is accompanied by a pronounced change of the underlying lattice structure of the aggregates from square-like to hexagonal ordering. Increasing the temperature we find a transformation to a fluid phase, consistent with results of a simple mean-field density functional theory

Intermixing at the InxSy/Cu2ZnSn(S,Se)4 Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

We report on the chemical and electronic structure of the interface between a thermally co-evaporated InxSy buffer and a Cu2ZnSn(S,Se)4 (CZTSSe) absorber for thin-film solar cells. To date, such cells have achieved energy conversion efficiencies up to 8.6%. Using surface-sensitive X-ray and UV photoelectron spectroscopy, combined with inverse photoemission and bulk-sensitive soft X-ray emission spectroscopy, we find a complex character of the buffer layer. It includes oxygen, as well as selenium and copper that diffused from the absorber into the InxSy buffer, exhibits an electronic band gap of 2.50 ± 0.18 eV at the surface, and leads to a small cliff in the conduction band alignment at the InxSy/CZTSSe interface. After an efficiency-increasing annealing step at 180 °C in nitrogen atmosphere, additional selenium diffusion leads to a reduced band gap at the buffer layer surface (2.28 ± 0.18 eV)

Minimal order H(div)-conforming velocity-vorticity approximations for incompressible fluids

We introduce a novel minimal order hybrid Discontinuous Galerkin (HDG) and a novel mass conserving mixed stress (MCS) method for the approximation of incompressible flows. For this we employ the $H(\operatorname{div})$-conforming linear Brezzi-Douglas-Marini space and the lowest order Raviart-Thomas space for the approximation of the velocity and the vorticity, respectively. Our methods are based on the physically correct diffusive flux $-\nu \varepsilon(u)$ and provide exactly divergence-free discrete velocity solutions, optimal (pressure robust) error estimates and a minimal number of coupling degrees of freedom. For the stability analysis we introduce a new Korn-like inequality for vector-valued element-wise $H^1$ and normal continuous functions. Numerical examples conclude the work where the theoretical findings are validated and the novel methods are compared in terms of condition numbers with respect to discrete stability parameters

Mapping Patent Classifications: Portfolio and Statistical Analysis, and the Comparison of Strengths and Weaknesses

The Cooperative Patent Classifications (CPC) jointly developed by the European and US Patent Offices provide a new basis for mapping and portfolio analysis. This update provides an occasion for rethinking the parameter choices. The new maps are significantly different from previous ones, although this may not always be obvious on visual inspection. Since these maps are statistical constructs based on index terms, their quality--as different from utility--can only be controlled discursively. We provide nested maps online and a routine for portfolio overlays and further statistical analysis. We add a new tool for "difference maps" which is illustrated by comparing the portfolios of patents granted to Novartis and MSD in 2016.Comment: Scientometrics 112(3) (2017) 1573-1591; http://link.springer.com/article/10.1007/s11192-017-2449-

Divergence-Conforming Velocity and Vorticity Approximations for Incompressible Fluids Obtained with Minimal Facet Coupling

We introduce two new lowest order methods, a mixed method, and a hybrid discontinuous Galerkin method, for the approximation of incompressible flows. Both methods use divergence-conforming linear Brezzi–Douglas–Marini space for approximating the velocity and the lowest order Raviart–Thomas space for approximating the vorticity. Our methods are based on the physically correct viscous stress tensor of the fluid, involving the symmetric gradient of velocity (rather than the gradient), provide exactly divergence-free discrete velocity solutions, and optimal error estimates that are also pressure robust. We explain how the methods are constructed using the minimal number of coupling degrees of freedom per facet. The stability analysis of both methods are based on a Korn-like inequality for vector finite elements with continuous normal component. Numerical examples illustrate the theoretical findings and offer comparisons of condition numbers between the two new methods

Multidirectional colloidal assembly in concurrent electric and magnetic fields

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Dipolar interactions between nano- and micron sized colloids lead to their assembly into domains with well-defined local order. The particles with a single dipole induced by an external field assemble into linear chains and clusters. However, to achieve the formation of multidirectionally organized nano-or microassemblies with tunable physical characteristics, more sophisticated interaction tools are needed. Here we demonstrate that such complex interactions can be introduced in the form of two independent, non-interacting dipoles (double-dipoles) within a microparticle. We show how this can be achieved by the simultaneous application of alternating current (AC)-electric field and uniform magnetic field to dispersions of superparamagnetic microspheres. Depending on their timing and intensity, concurrent electric and magnetic fields lead to the formation of bidirectional particle chains, colloidal networks, and discrete crystals. We investigate the mechanistic details of the assembly process, and identify and classify the non-equilibrium states formed. The morphologies of different experimental states are in excellent correlation with our theoretical predictions based on Brownian dynamics simulations combined with a structural analysis based on local energy parameters. This novel methodology of introducing and interpreting double-dipolar particle interactions may assist in the assembly of colloidal coatings, dynamically reconfigurable particle networks, and bidirectional active structures.DFG, GRK 1524, Self-Assembled Soft-Matter Nanostructures at Interface

Drip and Mate Operations Acting in Test Tube Systems and Tissue-like P systems

The operations drip and mate considered in (mem)brane computing resemble the operations cut and recombination well known from DNA computing. We here consider sets of vesicles with multisets of objects on their outside membrane interacting by drip and mate in two different setups: in test tube systems, the vesicles may pass from one tube to another one provided they fulfill specific constraints; in tissue-like P systems, the vesicles are immediately passed to specified cells after having undergone a drip or mate operation. In both variants, computational completeness can be obtained, yet with different constraints for the drip and mate operations