Viscous to Inertial Crossover in Liquid Drop Coalescence

Using an electrical method and high-speed imaging we probe drop coalescence down to 10 ns after the drops touch. By varying the liquid viscosity over two decades, we conclude that at sufficiently low approach velocity where deformation is not present, the drops coalesce with an unexpectedly late crossover time between a regime dominated by viscous and one dominated by inertial effects. We argue that the late crossover, not accounted for in the theory, can be explained by an appropriate choice of length-scales present in the flow geometry.Comment: 4 pages, 4 figure

Multiple transient memories in sheared suspensions: robustness, structure, and routes to plasticity

Multiple transient memories, originally discovered in charge-density-wave conductors, are a remarkable and initially counterintuitive example of how a system can store information about its driving. In this class of memories, a system can learn multiple driving inputs, nearly all of which are eventually forgotten despite their continual input. If sufficient noise is present, the system regains plasticity so that it can continue to learn new memories indefinitely. Recently, Keim & Nagel showed how multiple transient memories could be generalized to a generic driven disordered system with noise, giving as an example simulations of a simple model of a sheared non-Brownian suspension. Here, we further explore simulation models of suspensions under cyclic shear, focussing on three main themes: robustness, structure, and overdriving. We show that multiple transient memories are a robust feature independent of many details of the model. The steady-state spatial distribution of the particles is sensitive to the driving algorithm; nonetheless, the memory formation is independent of such a change in particle correlations. Finally, we demonstrate that overdriving provides another means for controlling memory formation and retention

Multiple transient memories in experiments on sheared non-Brownian suspensions

A system with multiple transient memories can remember a set of inputs but subsequently forgets almost all of them, even as they are continually applied. If noise is added, the system can store all memories indefinitely. The phenomenon has recently been predicted for cyclically sheared non-Brownian suspensions. Here we present experiments on such suspensions, finding behavior consistent with multiple transient memories and showing how memories can be stabilized by noise.Comment: 5 pages, 4 figure

Fundamentals of Traffic Flow

From single vehicle data a number of new empirical results concerning the density-dependence of the velocity distribution and its moments as well as the characteristics of their temporal fluctuations have been determined. These are utilized for the specification of some fundamental relations of traffic flow and compared with existing traffic theories.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm

Memory formation in matter

Memory formation in matter is a theme of broad intellectual relevance; it sits at the interdisciplinary crossroads of physics, biology, chemistry, and computer science. Memory connotes the ability to encode, access, and erase signatures of past history in the state of a system. Once the system has completely relaxed to thermal equilibrium, it is no longer able to recall aspects of its evolution. Memory of initial conditions or previous training protocols will be lost. Thus many forms of memory are intrinsically tied to far-from-equilibrium behavior and to transient response to a perturbation. This general behavior arises in diverse contexts in condensed matter physics and materials: phase change memory, shape memory, echoes, memory effects in glasses, return-point memory in disordered magnets, as well as related contexts in computer science. Yet, as opposed to the situation in biology, there is currently no common categorization and description of the memory behavior that appears to be prevalent throughout condensed-matter systems. Here we focus on material memories. We will describe the basic phenomenology of a few of the known behaviors that can be understood as constituting a memory. We hope that this will be a guide towards developing the unifying conceptual underpinnings for a broad understanding of memory effects that appear in materials

Nachhaltige Verbesserung der Verfügbarkeit ökologisch vermehrten Gemüsesaatguts für den Erwerbsanbau durch on-farm Erhaltung, Züchtung und Vermehrung

Die Verfügbarkeit von ökologisch vermehrtem Saatgut bzw. die Sortenauswahl wird insbesondere bei Gemüse als unzureichend eingestuft. Die verwendeten Sorten sind bei vielen Gemüsekulturen zum überwiegenden Teil Hybriden, die für eine /On-farm/-Erhaltung ungeeignet sind oder im Falle von aus Zellfusion (Protoplasten- oder Cytoplastenfusion) stammenden CMS-Hybriden nicht mehr fertil und auf Betrieben der Ökolandbauverbände per Richtlinie verboten sind. Diese beiden Aspekte der Saatgutfrage waren maßgebend für den Start dieses Projektes. Mit dem Ziel, die Eignung der Sorten für den ökologischen Gemüsebau zu prüfen, wurden 164 Saatgutmuster noch verfügbarer Populationssorten der Kulturen Kohlrabi (15), Möhren (86) und Porree (63) am europäischen Saatgutmarkt erworben und als Ausgangsmaterial für die Sichtungen verwendet. Dafür wurden an elf Standorten in Deutschland, den Niederlanden und der Schweiz über zwei Jahre 143 Sorten gesichtet und von mehr als der Hälfte der Sorten erhaltungszüchterischer Samenbau durchgeführt. Sorten, die auf Basis der Sichtungen als für den ökologischen Erwerbsgemüsebau unmittelbar geeignet eingestuft worden sind, werden in weiterführenden (teilweise externen) Versuchsanbau gestellt. Außerdem werden dafür ökologische Erhaltungszuchten bzw. Saatgutvermehrungen aufgebaut, die teilweise bereits in der Projektlaufzeit initiiert wurden. Sorten, die einer züchterischen Weiterentwicklung bedürfen, stehen als Ausgangsmaterial für ökologische Zuchtprogramme zur Verfügung. Das Saatgut wird über eine vereinseigene Genbank zentral verwaltet. Die Ergebnisse der Sichtungen, sowie Sortenbeschreibungen sind in einer Online-Datenbank veröffentlicht: www.kultursaat.org/index.ph

Photoassociative spectroscopy at long range in ultracold strontium

We report photoassociative spectroscopy of $^{88}$Sr$_2$ in a magneto-optical trap operating on the ${^1S_0}\to{^3P_1}$ intercombination line at 689 nm. Photoassociative transitions are driven with a laser red-detuned by 600-2400 MHz from the ${^1S_0}\to{^1P_1}$ atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the ${^1P_1}$ atomic lifetime ($\tau=5.22 \pm 0.03$ ns) and resolves a discrepancy between experiment and recent theoretical calculations.Comment: 4 pages, 4 figures, submitte

Generalized Intelligent States for an Arbitrary Quantum System

Generalized Intelligent States (coherent and squeezed states) are derived for an arbitrary quantum system by using the minimization of the so-called Robertson-Schr\"odinger uncertainty relation. The Fock-Bargmann representation is also considered. As a direct illustration of our construction, the P\"oschl-Teller potentials of trigonometric type will be shosen. We will show the advantage of the Fock-Bargmann representation in obtaining the generalized intelligent states in an analytical way. Many properties of these states are studied

Suppression of spin-state transition in epitaxially strained LaCoO_{3}

Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.Comment: 5 pages, 5 figures, submitted to Physical Review