Scaling of the linear response in simple ageing systems without disorder

The time-dependent scaling of the thermoremanent and zero-field-cooled susceptiblities in ferromagnetic spin systems undergoing ageing after a quench to a temperature at or below criticality is studied. A recent debate on their interpretation is resolved by showing that for systems with a short-ranged equilibrium spin-spin correlator and above their roughening temperature, the field-cooled susceptibility $\chi_{\rm FC}(t)-\chi_0\sim t^{-A}$ where $\chi_0$ is related to the equilibrium magnetization and the exponent A is related to the time-dependent scaling of the interface width between ordered domains. The same effect also dominates the scaling of the zero-field-cooled susceptibility $\chi_{\rm ZFC}(t,s)$, but does not enter into the thermoremanent susceptibility $\rho_{\rm TRM}(t,s)$. However, there may be large finite-time corrections to the scaling of $\rho_{\rm TRM}(t,s)$ which are explicitly derived and may be needed in order to extract reliable ageing exponents. Consistency with the predictions of local scale invariance is confirmed in the Glauber-Ising and spherical models.Comment: Latex2e, 14 pages, with 6 figure

Ein Gegenstand der Wohnkultur im Wandel, eine volkskundlich-archäologische Studie auf der Basis der Hildesheimer Quellen

Der Kachelofen stellt eine Novation von besonderer Bedeutung dar, die als eine der wesentlichen Grundlagen für die europäische Wohnkultur heutiger Prägung betrachtet werden kann. Erst mit Hilfe der Ofenheizung wurde ein Leben in rauchfrei heizbaren Räumen für breite Bevölkerungsschichten möglich. Die Entwicklung dieser häuslichen Heizungstechnologie über einen Zeitraum vom 13. - 18. Jahrhundert anhand archäologischer, bildlicher, historischer und bauhistorischer Quellen nachzuvollziehen, ist Zielsetzung der Studie ..

Pore-scale tomography and imaging: applications, techniques and recommended practice

[No abstract available

DMRG studies of the effect of constraint release on the viscosity of polymer melts

The scaling of the viscosity of polymer melts is investigated with regard to the molecular weight. We present a generalization of the Rubinstein-Duke model, which takes constraint releases into account and calculate the effects on the viscosity by the use of the Density Matrix Renormalization Group (DMRG) algorithm. Using input from Rouse theory the rates for the constraint release are determined in a self consistent way. We conclude that shape fluctuations of the tube caused by constraint release are not a likely candidate for improving Doi's crossover theory for the scaling of the polymer viscosity.Comment: 6 pages, 8 figure

Wet-chemical Passivation of Anisotropic Plasmonic Nanoparticles for LSPR-sensing by a Silica Shell

Metal nanoparticles showing the effect of localized surface plasmon resonance (LSPR), a collective oscillation of the conduction electrons upon interaction with light, represent an interesting tool for bioanalytics. This resonance is influenced by changes in the environment, and can be therefore used for the detection of molecular layers. The sensitivity, this means the extent of wavelength resonance shift per change in refractive index in the environment, represents an important performance parameter. It is higher for silver compared to gold particles, and is also increased for anisotropic particles. So silver triangles show a high potential for highly sensitive plasmonic nanoparticles. However, the stability under ambient conditions is rather poor. The paper demonstrates the passivation of silver triangles by silica coating using a wet-chemical approach. It compares the sensitivity for particles with and without passivation, and visualizes the passivation effect in a high resolution, single particle TEM study

Dilemmas of Sustainability: On Relevance and Critical Reflection in Sustainability Research; A Guide

The concept of sustainability is increasingly losing its contours. This study reflects on the understanding of sustainability used in research and science. Its authors thus enable us to concisely determine not only concrete contributions to sustainability, but also its limits. Based on an analytical understanding of sustainability and the basic structure of practical dilemmas, the book identifies typical conflicts as causes of dilemmas. Meta-criteria of sustainability allow us to identify dilemmas and to clarify and deal with them practically at an early stage. Finally, the study applies these meta-criteria in concrete project contexts by means of guiding questions for reflection.Der Begriff der Nachhaltigkeit verliert zunehmend an Kontur. Vor diesem Hintergrund gibt dieser Leitfaden die Möglichkeit, das jeweils verwendete Verständnis von Nachhaltigkeit in Forschung und Wissenschaft zu reflektieren und damit den konkreten Beitrag zu Nachhaltigkeit, aber auch die verbundenen Grenzen konkret festzustellen. Ausgehend von einem analytischen Nachhaltigkeitsverständnis und der Klärung der Grundstruktur praktischer Dilemmata benennt der Leitfaden typische Konflikte als Ursache von Dilemmata. Meta-Kriterien der Nachhaltigkeit erlauben, Dilemmata-Früherkennung, -Aufklärung und -Bearbeitung zu unterstützen. Diese werden abschließend mittels Reflexionsleitfaden für die Anwendung in konkreten Projektkontexten operationalisiert

Validation of pressure drop prediction and bed generation of fixed‐beds with complex particle shapes using discrete element method and computational fluid dynamics

Catalytic fixed‐bed reactors with a low tube‐to‐particle diameter ratio are widely used in industrial applications. The heterogeneous packing morphology in this reactor type causes local flow phenomena that significantly affect the reactor performance. Particle‐resolved computational fluid dynamics has become a predictive numerical method to analyze the flow, temperature, and species field, as well as local reaction rates spatially and may, therefore, be used as a design tool to develop new improved catalyst shapes. Most validation studies which have been presented in the past were limited to simple particle shapes. More complex catalyst shapes are supposed to increase the reactor performance. A workflow for the simulation of fixed‐bed reactors filled with various industrially relevant complex particle shapes is presented and validated against experimental data in terms of bed voidage and pressure drop. Industrially relevant loading strategies are numerically replicated and their impact on particle orientation and bed voidage is investigated.TU Berlin, Open-Access-Mittel – 202