University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Computer science & Context (language use). The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

Second harmonic generation spectroscopy on hybrid plasmonic/dielectric nanoantennas

Abstract: Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes. By placing a nonlinear dielectric nanoparticle in such a hot spot, one can hope to take advantage of both the field enhancement provided by nanoantennas and the large, nonlinear optical susceptibility of dielectric nanoparticles. To test this concept, we combine gold gap nanoantennas with second-order, nonlinear zinc sulfide nanoparticles, and perform second harmonic generation (SHG) spectroscopy on the combined hybrid dielectric/plasmonic nanoantennas as well as on the individual constituents. We find that SHG from the bare gold nanoantennas, even though it should be forbidden due to symmetry reasons, is several orders of magnitude larger than that of the bare zinc sulfide nanoparticles. Even stronger second harmonic signals are generated by the hybrid dielectric/plasmonic nanoantennas. Control experiments with nanoantennas containing linear lanthanum fluoride nanoparticles reveal; however, that the increased SHG efficiency of the hybrid dielectric/plasmonic nanoantennas does not depend on the nonlinear optical susceptibility of the dielectric nanoparticles but is an effect of the modification of the dielectric environment. The combination of a hybrid dielectric/plasmonic nanoantenna, which is only resonant for the incoming pump light field, with a second nanoantenna, which is resonant for the generated second harmonic light, allows for a further increase in the efficiency of SHG. As the second nanoantenna mediates the coupling of the second harmonic light to the far field, this double-resonant approach also provides us with control over the polarization of the generated light.

Advancing research on loyalty programs: a future research agenda

Abstract: Despite the growing literature on loyalty program (LP) research, many questions remain underexplored. Driven by advancements in information technology, marketing analytics, and consumer interface platforms (e.g., mobile devices), there have been many recent developments in LP practices around the world. They impose new challenges and create exciting opportunities for future LP research. The main objective of this paper is to identify missing links in the literature and to craft a future research agenda to advance LP research and practice. Our discussion focuses on three key areas: (1) LP designs, (2) Assessment of LP performance, and (3) Emerging trends and the impact of new technologies. We highlight several gaps in the literature and outline research opportunities in each area.

Blow-up prevention by quadratic degradation in a two-dimensional Keller–Segel–Navier–Stokes system

Abstract: This paper deals with an initial-boundary value problem in a two-dimensional smoothly bounded domain for the Keller–Segel–Navier–Stokes system with logistic source, as given by $$\begin{aligned} \left\{ \begin{array}{rcl} n_t + u\cdot abla n &{} =&{} \Delta n - abla \cdot (n abla c)+rn-\mu n^2,\\ c_t + u\cdot abla c &{}=&{} \Delta c -c +n,\\ u_t + u\cdot abla u &{}=&{} \Delta u - abla P+n abla \phi +g,\\ abla \cdot u &{} =&{} 0, \end{array} \right. \end{aligned}$$ which describes the mutual interaction of chemotactically moving microorganisms and their surrounding incompressible fluid. It is shown that whenever \(\mu >0\), \(r\ge 0\), \(g\in C^1(\bar{\Omega }\times [0,\infty )) \cap L^\infty (\Omega \times (0,\infty )) \) and the initial data \((n_0, c_0, u_0)\) are sufficiently smooth fulfilling \(n_0 ot \equiv 0\), the considered problem possesses a global classical solution which is bounded. Moreover, if \(r=0\), then this solution satisfies $$\begin{aligned} n(\cdot ,t)\rightarrow 0 \quad \hbox {and} \quad c(\cdot ,t)\rightarrow 0 \quad \hbox {in } L^\infty (\Omega ) \end{aligned}$$ as \(t\rightarrow \infty \), and if additionally \(\int \limits _0^\infty \int \limits _\Omega |g(x,t)|^2 \hbox {d}x\hbox {d}t < \infty \), then all solution components decay in the sense that $$\begin{aligned} n(\cdot ,t)\rightarrow 0, \quad c(\cdot ,t)\rightarrow 0 \quad \hbox {and} \quad u(\cdot ,t)\rightarrow 0 \quad \hbox {in } L^\infty (\Omega ) \end{aligned}$$ as \(t\rightarrow \infty \).

Responsive hydrogel layers—from synthesis to applications

Abstract: Responsive polymer networks are interesting materials for a variety of different applications due to the fact that they can perform a large volume transition. However, the swelling transition is a diffusion limited process. Thus, the decrease of the feature size (e.g., in thin layers) is an appropriate way to create structures with reasonable response time. The possibility to pattern responsive polymer networks makes them useful for application in microsystem technology as well as in biomedicine. The transition behavior of these films showed similar trends to those of the corresponding linear polymers whereas confinement effects have been found for thin hydrogel layers. The ability to optimize the integration of these polymers is critical for the fabrication and development of platforms that harness the unique abilities of responsive polymer networks. Here, recent developments on chemically cross-linked hydrogel layers with respect to synthesis, characterization, and application are highlighted.