Price Setting in Online Grocery Markets: The Case of Chocolate

Online markets are developing rapidly in many industrialized countries and have already reached a rather mature status for some product categories. This, however, is not the case in the food sector. In Germany, the online food market captured still less than 1 % of total food sales in 2014. Despite this small share of the online market, the segment is clearly increasing and major players on the offline grocery market engage themselves on the online market, too, or they plan to do so. It is intended in this paper to contribute to our knowledge on competitive strategies of multichannel suppliers and pure online traders which are active on this growing market segment. A major element of competitive strategies on the online market for foods is pricing. We concentrate on pricing strategies of multichannel firms and pure online traders on the German online market and present evidence for the product group chocolate

Signature of odd-frequency pairing correlations induced by a magnetic interface

We investigate the mutual proximity effect in a normal metal contacted to a superconductor through a magnetic interface. Analytical and self-consistent numerical results are presented, and we consider both the diffusive and ballistic regimes. We focus on the density of states in both the normal and superconducting region, and find that the presence of spin-dependent phase-shifts occurring at the interface qualitatively modifies the density of states. In particular, we find that the proximity-induced pairing amplitudes in the normal metal region undergo a conversion at the Fermi level from pure even-frequency to odd-frequency. Above a critical value of the interface spin-polarization (or, equivalently, for fixed interface spin-polarization, above a critical interface resistance), only odd frequency correlations remain. This is accompanied by the replacement of the familiar proximity minigap or pseudogap in the normal layer by an enhancement of the density of states above its normal state value for energies near the chemical potential. The robustness of this effect towards inelastic scattering, impurity scattering, and the depletion of the superconducting order parameter close to the interface is investigated. We also study the inverse proximity effect in the diffusive limit. We find that the above-mentioned conversion persists also for thin superconducting layers comparable in size to the superconducting coherence length $\xi_\text{S}$, as long as the inverse proximity effect is relatively weak. Concomitantly, we find a shift in the critical interface resistance where the pairing conversion occurs. Our findings suggest a robust and simple method for producing purely odd-frequency superconducting correlations, that can be tested experimentally.Comment: 14 pages, 12 figures. Submitted to Physical Review. Chosen as Editors' Suggestio

How German Online Retailers Price Foods: An Empirical Analysis for Chocolate Products

Despite the increasing importance of online grocery retailing, little is known about price dispersion across online providers, the relation between online and offline prices as well as the frequency of price adjustments. We employ means of descriptive and inductive statistics as well as panel econometrics to address these issues for German online food retailers. Daily online prices for twelve chocolate products charged by eight pure online and multichannel retailers and collected over three months are investigated. Information economics suggests that a maturing online market will call forth more price homogeneity online due to lower search costs by consumers as well as more flexible prices due to lower costs of price adjustments by retailers. Our results suggest, however, that neither homogenous prices nor frequent price adjustments do occur on the German online chocolate market

Novel Superconducting States in Hybrid Devices

We discuss different scenarios which allow for inducing unconventional superconducting pairing correlations in heterostructures. Specifically, we investigate superconductor-ferromagnet hybrids using a recent extension of the Quasiclassical Theory of Superconductivity and discuss both the long range triplet Josephson effect and point contact spectra. In the second part, we investigate a microscopic model of the superconducting proximity effect in topological insulators

A Numerical Study of the Superconducting Proximity Effect in Topological Surface States

We study the superconducting proximity effect induced in the surface states of the 3-d topological insulator Bi$_2$Se$_3$ by a singlet, s-wave superconductor deposited on its surface. To this effect, the $\mathbf{k}\cdot\mathbf{p}$-Hamiltonian of Bi$_2$Se$_3$ and the BCS-Hamiltonian are mapped onto tight-binding chains which we couple through a transfer-Hamiltonian at the interface. We then employ the Recursive Green's Function technique to obtain the local spectral function and infer the dispersion of the interface-states from it. In agreement with earlier microscopic studies of this problem, we find that the Fu-Kane model is a reasonable approximation at energies $\epsilon\ll \Delta_{\rm SC}$. However, for energies close to the SC bulk gap, the Fu-Kane model is expected to break down. Indeed, our numerical calculations show strong modifications of the interface-state dispersion for $\epsilon \gtrsim \Delta_{\rm SC}$. We find that the proximity effect can be strong enough to induce a gap in the surface state that is comparable to the superconducting gap. An analysis of the spatial profile of the states shows that their weight shifts towards the SC as the coupling strength increases. We conclude that an intermediate coupling is ideal for realising the Fu-Kane scenario.Comment: JOP: Conference Series (Proceedings of SCES 2011), accepte

Theory of superconductor-ferromagnet point-contact spectra: The case of strong spin polarization

We study the impact of spin-active scattering on Andreev spectra of point contacts between superconductors (SC) and strongly spin-polarized ferromagnets (FM) using recently derived boundary conditions for the quasiclassical theory of superconductivity. We describe the interface region by a microscopic model for the interface scattering matrix. Our model includes both spin filtering and spin mixing and is nonperturbative in both transmission and spin polarization. We emphasize the importance of spin-mixing caused by interface scattering, which has been shown to be crucial for the creation of exotic pairing correlations in such structures. We provide estimates for the magnitude of this effect in different scenarios and discuss its dependence on various physical parameters. Our main finding is that the shape of the interface potential has a tremendous impact on the magnitude of the spin-mixing effect. Thus, all previous calculations, being based on delta-function or box-shaped interface potentials, underestimate this effect gravely. As a consequence, we find that with realistic interface potentials the spin-mixing effect can easily be large enough to cause spin-polarized subgap Andreev bound states in SC/FM point contacts. In addition, we show that our theory generalizes earlier models based on the Blonder-Tinkham-Klapwijk approach

Inverse proximity effect and influence of disorder on triplet supercurrents in strongly spin-polarized ferromagnets

We discuss the Josephson effect in strongly spin-polarized ferromagnets where triplet correlations are induced by means of spin-active interface scattering, extending our earlier work [Phys. Rev. Lett. 102, 227005 (2009)] by including impurity scattering in the ferromagnetic bulk and the inverse proximity effect in a fully self-consistent way. Our quasiclassical approach accounts for the differences of Fermi momenta and Fermi velocities between the two spin bands of the ferromagnet, and thereby overcomes an important short-coming of previous work within the framework of Usadel theory. We show that non-magnetic disorder in conjunction with spin-dependent Fermi velocities may induce a reversal of the spin-current as a function of temperature.Comment: 12 pages, 9 figure

Complications and Short-Term Explantation Rate Following Artificial Urinary Sphincter Implantation: Results from a Large Middle European Multi-Institutional Case Series

Background/Aims/Objectives: To analyze perioperative complication and short-term explantation rates after perineal or penoscrotal single-cuff and double-cuff artificial urinary sphincter (AUS) implantation in a large middle European multi-institutional patient cohort. Methods: 467 male patients with stress urinary incontinence underwent implantation of a perineal single-cuff (n = 152), penoscrotal single-cuff (n = 99), or perinea! double-cuff (n = 216) AUS between 2010 and 2012. Postoperative complications and 6-month explantation rates were assessed. For statistical analysis, Fisher's exact test and Kruskal Wallis rank sum test, and a multiple logistic regression model were used (p < 0.05). Results: Compared to perineal single-cuff AUS, penoscrotal single-cuff implantation led to significantly increased short-term explantation rates (8.6% (perinea)) vs. 19.2% (penoscrotal), p = 0.019). The postoperative infection rate was significantly higher after double-cuff compared to single cuff implantation (6.0% (single-cuff) vs. 13.9% (double-cuff), p = 0.019). The short-term explantation rate after primary double-cuff placement was 6.5% (p = 0.543 vs. perineal single -cuff). In multivariate analysis, the penoscrotal approach (p = 0.004), intraoperative complications (p = 0.005), postoperative bleeding (p = 0.011), and perioperative infection (p < 0.001) were independent risk factors for short-term explantation. Conclusions: Providing data from a large contemporary multi-institutional patient cohortfrom high-volume and low-volume institutions, our results reflect the current standard of care in middle Europe. We indicate that the penoscrotal approach is an independent risk factor for increased short-term explantation rates. (C) 2016 S. Karger AG, Base