Human-Centric Chronographics:Making Historical Time Memorable

A series of experiments is described, evaluating user recall of visualisations of historical chronology. Such visualisations are widely created but have not hitherto been evaluated. Users were tested on their ability to learn a sequence of historical events presented in a virtual environment (VE) fly-through visualisation, compared with the learning of equivalent material in other formats that are sequential but lack the 3D spatial aspect. Memorability is a particularly important function of visualisation in education. The measures used during evaluation are enumerated and discussed. The majority of the experiments reported compared three conditions, one using a virtual environment visualisation with a significant spatial element, one using a serial on-screen presentation in PowerPoint, and one using serial presentation on paper. Some aspects were trialled with groups having contrasting prior experience of computers, in the UK and Ukraine. Evidence suggests that a more complex environment including animations and sounds or music, intended to engage users and reinforce memorability, were in fact distracting. Findings are reported in relation to the age of the participants, suggesting that children at 11–14 years benefit less from, or are even disadvantaged by, VE visualisations when compared with 7–9 year olds or undergraduates. Finally, results suggest that VE visualisations offering a ‘landscape’ of information are more memorable than those based on a linear model. Keywords: timeline, chronographic

Dynamic pathway of the photoinduced phase transition of TbMnO3_3

We investigate the demagnetization dynamics of the cycloidal and sinusoidal phases of multiferroic TbMnO$_3$ by means of time-resolved resonant soft x-ray diffraction following excitation by an optical pump. Using orthogonal linear x-ray polarizations, we suceeded in disentangling the response of the multiferroic cycloidal spin order from the sinusoidal antiferromagnetic order in the time domain. This enables us to identify the transient magnetic phase created by intense photoexcitation of the electrons and subsequent heating of the spin system on a picosecond timescale. The transient phase is shown to be a spin density wave, as in the adiabatic case, which nevertheless retains the wave vector of the cycloidal long range order. Two different pump photon energies, 1.55 eV and 3.1 eV, lead to population of the conduction band predominantly via intersite $d$-$d$ transitions or intrasite $p$-$d$ transitions, respectively. We find that the nature of the optical excitation does not play an important role in determining the dynamics of magnetic order melting. Further, we observe that the orbital reconstruction, which is induced by the spin ordering, disappears on a timescale comparable to that of the cycloidal order, attesting to a direct coupling between magnetic and orbital orders. Our observations are discussed in the context of recent theoretical models of demagnetization dynamics in strongly correlated systems, revealing the potential of this type of measurement as a benchmark for such complex theoretical studies

Tuning the multiferroic mechanisms of TbMnO3 by epitaxial strain

A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric measurements show an enormous increase of the ferroelectric polarization, and a change in its direction from along the c- to the a-axis. Our results suggest that the drastic change of multiferroic properties results from a switch of the spin-current magnetoelectric coupling in bulk TbMnO3 to symmetric magnetostriction in epitaxially-strained TbMnO3. These findings experimentally demonstrate that epitaxial strain can be used to control single-phase spin-driven multiferroic states

Miocene high elevation and high relief in the Central Alps

Reconstructing Oligocene–Miocene paleoelevation contributes to our understanding of the evolutionary history of the European Alps and sheds light on geodynamic and Earth surface processes involved in the development of Alpine topography. Despite being one of the most intensively explored mountain ranges worldwide, constraints on the elevation history of the European Alps remain scarce. Here we present stable and clumped isotope measurements to provide a new paleoelevation estimate for the mid-Miocene (∼14.5 Ma) European Central Alps. We apply stable isotope δ–δ paleoaltimetry to near-sea-level pedogenic carbonate oxygen isotope (δ18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate hydrogen isotope (δD) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable (δ18O, δ13C) and clumped (Δ47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate δ18O values and Δ47 temperatures (30±5 ∘C) yield a near-sea-level precipitation δ18Ow value of -5.8±1.2‰ and, in conjunction with the high-Alpine phyllosilicate δD value of  -14.6±0.3‰, suggest that the region surrounding the Simplon Fault Zone attained surface elevations of >4000 m no later than the mid-Miocene. Our near-sea-level δ18Ow estimate is supported by paleoclimate (iGCM ECHAM5-wiso) modeled δ18O values, which vary between −4.2 ‰ and −7.6 ‰ for the Northern Alpine Foreland Basin

Terahertz-Driven Nonlinear Spin Response of Antiferromagnetic Nickel Oxide

Terahertz magnetic fields with amplitudes of up to 0.4 Tesla drive magnon resonances in nickel oxide while the induced dynamics is recorded by femtosecond magneto-optical probing. We observe distinct spin-mediated optical nonlinearities, including oscillations at the second harmonic of the 1 THz magnon mode. The latter originate from coherent dynamics of the longitudinal component of the antiferromagnetic order parameter, which are probed by magneto-optical effects of second order in the spin deflection. These observations allow us to dynamically disentangle electronic from lattice-related contributions to magnetic linear birefringence and dichroism-information so far only accessible by ultrafast THz spin control. The nonlinearities discussed here foreshadow physics that will become essential in future subcycle spin switching

Interaktionstechniken und -tracking in der Visualisierung von Graphen

Die Untersuchung von Beteiligungsstrukturen ist für die Finanzbranche von großer Bedeutung. Beteiligungsstrukturen ergeben sich aus Beteiligungen von Unternehmen an anderen Unternehmen. Es gibt verschiedene Strukturen der Unternehmensnetzwerke mit daraus resultierenden Effekten wie einer höheren Rendite für die Anleger. Für die Analyse der Beteiligungsstrukturen ist eine Visualisierung der Unternehmensnetzwerke ein effektives Mittel. Eine effiziente Untersuchung des Datenbestandes benötigt geeignete Interaktionstechniken, die unter anderem dafür sorgen, dass die Menge an betrachteten Daten überschaubar ist. Dies kann beispielsweise durch Filterung der Daten oder Hervorhebung von strukturellen Motiven im Graphen der Unternehmensnetzwerke geschehen. Es ist dabei von großer Bedeutung alle durchgeführten Interaktionen mit dem Programm aufzuzeichnen und ihm für eine Visualisierung zur Verfügung zu stellen. Dies bietet die Möglichkeit eigene Arbeitsprozesse zu verstehen, zu reproduzieren und zu optimieren. Dadurch kann sowohl eine Optimierung der Benutzung der Software als auch der Software selbst erreicht werden. In dieser Bachelor-Thesis werden für das Softwaresystem RelaNet, ein Graphenprogramm mit speziellen Funktionen zur Analyse von Beteiligungsstrukturen, Interaktionstechniken, wie Filterung, Hervorhebung und Aggregation, auf Basis einer Suche über Knoten- und Kantenattribute, implementiert. Der Benutzer kann seine Datenanalyse in RelaNet folglich gezielter durchführen und vereinfachen, da nur eine Auswahl der Daten visualisiert bzw. fokussiert wird. Des Weiteren wird ein Tracking in RelaNet implementiert, welches die getätigten Benutzerschritte speichert, auch über eine Benutzersitzung hinaus, visualisiert, eine Navigation zwischen den Programmzuständen ermöglicht und schließlich eine Analyse der Vorgehensweise des Benutzers erlaubt. Anhand einer Fallstudie werden die Funktionsweise und die Vorteile dieser Implementierung mit einer Datenbank von 12 000 deutschen Unternehmen vorgeführt. In diesem Beispiel werden die verbesserten Möglichkeiten zur Analyse aufgezeigt, welche durch die Interaktionstechniken in Kombination mit dem Tracking möglich sind. Der Einsatz in anderen Systemen zur Informationsvisualisierung wie der Biologie oder des Supply Chain Managements ist genauso denkbar. The analysis of corporate structures has high importance for the financial sector. Corporate structures consist of companies holding shares in other companies. For analyzing corporate structures a graphical visualization of these networks is an effective instrument. An efficient analysis needs adequate interaction techniques, which for example allow restrict the amount of visualized data. This can be achieved by filtering the data or highlighting of structural motifs in the graphs representing the corporate structures. It is significant for the user's work to visualize her sequence of interactions with software systems and analyze them. This enables the user to understand, reproduce and optimize her work process, resulting in an optimization in usage of the software and optimization of the software itself. This bachelor thesis extends RelaNet, a program for visualizing graphs with specialized functions for analyzing corporate structures, by implementing interaction techniques, like filtering, highlighting and aggregation, based on a search for vertex and edge attributes. The user achieves a more tightly focused and easier analysis, because of a more focused visualization of data. Furthermore a tracking will be implemented, which saves user actions, beyond one session, visualize them, allows navigation between program states and thus enables an analysis of the user's analytical process. With the help of a case study the functionality and advantages of the presented implementation are shown. The case study uses a database containing 12 000 German corporations. The case study shows how a better analysis is possible by using the new interaction techniques in combination with the tracking system. The usage in other information visualization software such as for biology or supply chain management is also possible

Probing Ferroelectric Domain Engineering in BiFeO3 Thin Films by Second Harmonic Generation

ISSN:0935-9648ISSN:1521-409