Detection of the first X-ray selected large AGN group

We have examined the spatial distribution of 856 AGN detected by the ROSAT All-Sky Survey (RASS) using a direct search for structures with the minimal spanning tree. The AGNs were compiled from an area of 7000 deg^2, in which optical identifications of RASS sources were made with the help of the digitized objective prism plates of the Hamburg Quasar Survey (HQS). Redshifts were taken from the literature or from own follow-up observations. The sample probes the spatial distribution at low redshifts, since the redshift distribution peaks at z=0.1. The application of the minimal spanning tree led to a 1.8 sigma discovery of an AGN group with 7 members in a volume V=140*75*75 h^-3Mpc^3 in the Pisces constellation. With a mean redshift z=0.27 this group is only the third discovered group at redshifts z<0.5. The RASS offers excellent possibilities to study large scale structure with AGNs at low redshifts, once these redshifts are determined.Comment: 6 pages, 4 figures, accepted for publication in MNRA

DISCOVERING THE ROLE OF SCENARIO PLANNING AS AN EVALUATION METHODOLOGY FOR BUSINESS MODELS IN THE ERA OF THE INTERNET OF THINGS (IOT)

Within both scientific literature and practice, there is limited understanding about the evaluation aspect of business model innovation (BMI), especially in the context of digitalization and the Internet of Things (IoT). The aim of our research project is to contribute by validating whether methodologies from strat-egy, such as scenario planning, are appropriate means for evaluating business models in this explicit context. Following a Design Science Research (DSR) approach, we develop an approach to implement scenario planning into a BMI process respective of the features. In cooperation with business innovation employees of a well-known corporation in the technology sector, we apply the methodology to real-world innovation projects, empirically validate its viability, and determine how and to what extent it can be used. As a further result, we aim to scientifically expound its effects on creating competitive strategic advantages in the context of digitalization and the IoT

Magneto-Optical Reflection Spectroscopy with Linear Polarised Synchrotron Radiation on Monocrystalline Fe, Co, and Ni Thin Films

Die Entwicklung und Erforschung neuer auf magnetischen Materialien basierenden Systeme, z.B. für die Spintronik, schreitet stetig voran. Zur Untersuchung und Charakterisierung solcher magnetischer Materialien haben sich magneto-optische Spektroskopiemethoden mit polarisierter Synchrotronstrahlung fest etabliert. In der vorliegenden Arbeit wurden systematisch die ferromagnetischen Übergangsmetalle Fe, Co und Ni in kristalliner Form mittels magneto-optischer Reflexionsspektroskopie an den 3p- und 2p-Kanten untersucht. Im Gegensatz zur häufig genutzten Elektronenspektroskopie zeigt sich die Reflexionsspektroskopie als photon-in – photon-out Methode vor allem im extremen Ultraviolet (EUV) an den 3p-Kanten als besonders gut geeignet, da das Reflexionsvermögen der Proben in diesem Energiebereich auch für senkrechten Lichteinfall leicht messbar ist. In jüngster Zeit konzentriert sich die Forschung auf die Beeinflussung magnetischer und elektronischer Eigenschaften durch kristalline Anisotropie und deren Detektion mittels magneto-optischer Spektroskopiemethoden. Hierzu existieren bisher nur einige wenige Messungen, hauptsächlich an den 2p-Kanten von Fe-, Co- und Ni-Verbindungen. Das Hauptaugenmerk der Arbeit liegt auf dem Einfluss der magnetokristallinen Anisotropie auf magneto-optische Effekte an den 3p-Kanten von reinem Fe, Co und Ni. Es kann gezeigt werden, dass sich der transversale und der longitudinale magneto-optische Kerr-Effekt (L-MOKE und T-MOKE), welche linear in der Magnetisierung sind, als ungeeignet erweisen die Orientierung der magnetischen Momente im Kristall zu detektieren. In dieser Arbeit steht daher der magnetische Röntgenlineardichroismus (XMLD), welcher quadratisch in der Magnetisierung ist, im Vordergrund. Es konnte hier erstmalig gezeigt werden, dass der XMLD auch an den 3p-Kanten sehr empfindlich auf die Orientierung der Magnetisierung bezüglich der Kristallachsen reagiert. Dabei erfahren die XMLD-Spektren für unterschiedliche Orientierung des Kristalls Änderungen von bis zu 100%. In Kombination mit den Vorteilen der Reflexionsspektroskopie macht dies den XMLD zu einem hervorragenden Werkzeug um magnetische kristalline Strukturen zu untersuchen. Zudem wird gezeigt, dass Interferenzeffekte einen entscheidenden Einfluss auf die mittels Reflexionsspektroskopie gemessenen Spektren haben können. Im Gegensatz zu T-MOKE zeigt sich der XMLD an den 3p-Kanten jedoch wesentlich unanfälliger gegen störende Einflüsse von Interferenz. Zur Detektion des XMLD, der in etwa eine Größenordnung geringer ausfällt als z.B. T-MOKE, wurden im Rahmen dieser Arbeit umfangreiche Experimentiervorrichtungen entwickelt, aufgebaut und in Betrieb genommen. Ein weiterer Schwerpunkt dieser Arbeit ist die Validierung theoretischer Bandstrukturmodelle. Die vorgestellten experimentellen Spektren werden mit ab initio Rechnungen verglichen und es werden Rückschlüsse auf die Anwendbarkeit eines Ein-Elektronen-Ansatzes gezogen. Dabei konnte gezeigt werden, dass ab initio Rechnungen mittels LSDA die XMLD-Spektren an den 3p-Kanten von Fe sehr gut reproduzieren können. Zudem wird ein Modell vorgestellt, welches es erlaubt die Austauschaufspaltung der Rumpfzustände direkt in den XMLD-Spektren zu identifizieren. Die in der Arbeit systematisch durchgeführte Untersuchung des XMLD erweitert somit das Verständnis des magnetischen Röntgenlineardichroismus auf den Energiebereich des EUV und kann als Grundstein für zukünftige Anwendungen dienen, welche diesen Energiebereich nutzen.The development and investigation of new electronic systems based on magnetic materials, e.g. in spintronics, is still in progress. To characterise and explore such magnetic materials the magneto-optical spectroscopies with polarized synchrotron radiation are an established tool. This thesis deals with the systematic exploration of the ferromagnetic transition metals Fe, Co, and Ni at their 3p and 2p edges using reflection spectroscopy. In contrast to the often used total electron yield technique the reflection spectroscopy as a photon-in – photon-out method is appropriate especially in the extreme ultra violet (XUV) at the 3p edges because of the good sample reflectance in this energy range even at normal incidence. Recently, the influence on electronic and magnetic properties by crystalline anisotropy and its detection with magneto optical spectroscopies comes into the focus of research. Up to now only a few measurements exist mainly at the 2p edges of Fe, Co, and Ni alloys. The main part of this thesis deals with the influence of the magnetocrystalline anisotropy on magneto optical effects at the 3p edges of pure Fe, Co, and Ni. It can be shown that the longitudinal and the transversal magneto-optical Kerr effect (L-MOKE and T-MOKE), which are linear in magnetisation, are inapplicable to detect the orientation of the magnetic moments in the crystal. Therefore, this thesis is focused on the x-ray magneitc linear dichroism (XMLD), which is quadratic in magentization. It can be shown for the first time that also at the 3p edge the XMLD is very sensitive to the magnetization orientation within the crystal. The XMLD signal undergoes changes up to 100% when changing the orientation of the crystal. In combination with the advantages of reflection spectroscopy the XMLD turns out as a perfectly suitable tool for the investigation of magnetic crystal structures. Additionally in this thesis it is shown that interference effects can have a drastic impact on the magneto-optical spectra measured in reflection but in contrast to T-MOKE the XMLD at the 3p edges is nearly unaffected by interference effects. To detect the XMLD, which is about one order of magnitude smaller than e.g. T-MOKE, versatile experimental devices have been developed and deployed within the scope of this thesis. A second main aspect of this thesis is the validation of theoretical band structure models. The presented experimental spectra are compared with ab initio calculations and the applicability of an one electron model is discussed. It is shown that with an LSDA approach the XMLD spectra of Fe can be described very well. In addition a simple model is introduced which allows to identify the core level exchange splitting directly within the spectral structures of the XMLD. The systematic investigations of the XMLD at the 3p edges presented in this thesis expands the understanding of the XMLD to the energy range of the XUV and can be used as a foundation for future experiments using this energy range

The yellow European eel (Anguilla anguilla L.) may adopt a sedentary lifestyle in inland freshwaters

We analysed the movements of the growing yellow phase using a long-term mark–recapture programme on European eels in a small catchment (the Frémur, France). The results showed that of the yellow eels (>200 mm) recaptured, more than 90% were recaptured at the original marking site over a long period before the silvering metamorphosis and downstream migration. We conclude that yellow European eels >200 mm may adopt a sedentary lifestyle in freshwater area, especially in small catchment

Helping education undergraduates to use appropriate criteria for evaluating accounts of motivation

The aim of the study was to compare students in a control group with those in a treatment group with respect to evaluative comments on psychological accounts of motivation. The treatment group systematically scrutinized the nature and interpretation of evidence that supported different accounts, and the assumptions, logic, coherence and clarity of accounts. Content analysis of 74 scripts (using three categories) showed that the control group students made more assertions than either evidential or evaluative points, whereas the treatment group used evaluative statements as often as they used assertion. The findings provide support for privileging activities that develop understanding of how knowledge might be contested, and suggest a need for further research on pedagogies to serve this end. The idea is considered that such understanding has a pivotal role in the development of critical thinking

Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations

This study presents a historical review, a meta-analysis, and recommendations for users about weight–length relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weight–length relationships of the type W = aLb for 1773 species of fishes. It shows that 82% of the variance in a plot of log a over b can be explained by allometric versus isometric growth patterns and by different body shapes of the respective species. Across species median b = 3.03 is significantly larger than 3.0, thus indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes. The expected range of 2.5 < b < 3.5 is confirmed. Mean estimates of b outside this range are often based on only one or two weight–length relationships per species. However, true cases of strong allometric growth do exist and three examples are given. Within species, a plot of log a vs b can be used to detect outliers in weight–length relationships. An equation to calculate mean condition factors from weight–length relationships is given as Kmean = 100aLb−3. Relative weight Wrm = 100W/(amLbm) can be used for comparing the condition of individuals across populations, where am is the geometric mean of a and bm is the mean of b across all available weight–length relationships for a given species. Twelve recommendations for proper use and presentation of weight–length relationships, condition factors and relative weight are given

Generalizing Murray's law : an optimization principle for fluidic networks of arbitrary shape and scale

Murray's law states that the volumetric flow rate is proportional to the cube of the radius in a cylindrical channel optimized to require the minimum work to drive and maintain the fluid. However, application of this principle to the biomimetic design of micro/nano fabricated networks requires optimization of channels with arbitrary cross-sectional shape (not just circular) and smaller than is valid for Murray's original assumptions. We present a generalized law for symmetric branching that (a) is valid for any cross-sectional shape, providing that the shape is constant through the network; (b) is valid for slip flow and plug flow occurring at very small scales; and (c) is valid for networks with a constant depth, which is often a requirement for lab-on-a-chip fabrication procedures. By considering limits of the generalized law, we show that the optimum daughter-parent area ratio Γ, for symmetric branching into N daughter channels of any constant cross-sectional shape, is Γ=N−2/3Γ=N−2/3 for large-scale channels, and Γ=N−4/5Γ=N−4/5 for channels with a characteristic length scale much smaller than the slip length. Our analytical results are verified by comparison with a numerical optimization of a two-level network model based on flow rate data obtained from a variety of sources, including Navier-Stokes slip calculations, kinetic theory data, and stochastic particle simulations

Nonlinear Dynamic Modeling and Controls Development for Supersonic Propulsion System Research

This paper covers the propulsion system component modeling and controls development of an integrated nonlinear dynamic simulation for an inlet and engine that can be used for an overall vehicle (APSE) model. The focus here is on developing a methodology for the propulsion model integration, which allows for controls design that prevents inlet instabilities and minimizes the thrust oscillation experienced by the vehicle. Limiting thrust oscillations will be critical to avoid exciting vehicle aeroelastic modes. Model development includes both inlet normal shock position control and engine rotor speed control for a potential supersonic commercial transport. A loop shaping control design process is used that has previously been developed for the engine and verified on linear models, while a simpler approach is used for the inlet control design. Verification of the modeling approach is conducted by simulating a two-dimensional bifurcated inlet and a representative J-85 jet engine previously used in a NASA supersonics project. Preliminary results are presented for the current supersonics project concept variable cycle turbofan engine design