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- Patholinguistik (19)
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- Sonderforschungsbereich 632 - Informationsstruktur (5)
We present results of full 3D hydrodynamical and radiative transfer simulations of the colliding stellar winds in the massive binary system η Carinae. We accomplish this by applying the SimpleX algorithm for 3D radiative transfer on an unstructured Voronoi-Delaunay grid to recent 3D smoothed particle hydrodynamics (SPH) simulations of the binary colliding winds. We use SimpleX to obtain detailed ionization fractions of hydrogen and helium, in 3D, at the resolution of the original SPH simulations. We investigate several computational domain sizes and Luminous Blue Variable primary star mass-loss rates. We furthermore present new methods of visualizing and interacting with output from complex 3D numerical simulations, including 3D interactive graphics and 3D printing. While we initially focus on η Car, the methods employed can be applied to numerous other colliding wind (WR 140, WR 137, WR 19) and dusty `pinwheel' (WR 104, WR 98a) binary systems. Coupled with 3D hydrodynamical simulations, SimpleX simulations have the potential to help determine the regions where various observed time-variable emission and absorption lines form in these unique objects.
We present 3D numerical simulations of the NGC6888 nebula considering the proper motion and the evolution of the star, from the red supergiant (RSG) to the Wolf-Rayet (WR) phase. Our simulations reproduce the limb-brightened morphology observed in [OIII] and X-ray emission maps. The synthetic maps computed by the numerical simulations show filamentary and clumpy structures produced by instabilities triggered in the interaction between the WR wind and the RSG shell.
The main objective of this work is to investigate the evolution of massive stars, and the interplay between them and the ionized gas for a sample of local metal-poor Wolf-Rayet galaxies.
Optical integral field spectrocopy was used in combination with multi-wavelength radio data.
Combining optical and radio data, we locate Wolf-Rayet stars and supernova remnants across the Wolf-Rayet galaxies to study the spatial correlation between them. This study will shed light on the massive star formation and its feedback, and will help us to better understand
distant star-forming galaxies.
We analyse whether a stellar atmosphere model computed with the code CMFGEN provides an optimal description of the stellar observations of WR 136 and simultaneously reproduces the nebular observations of NGC 6888, such as the ionization degree, which is modelled with the pyCloudy code. All the observational material available (far and near UV and optical spectra) were used to constrain such models. We found that the stellar temperature T∗, at τ = 20, can be in a range between 70 000 and 110 000 K, but when using the nebula as an additional restriction, we found that the stellar models with T∗ ∼ 70 000 K represent the best solution for both, the star and the nebula.
We suggest several ideas which when combined could lead to a new mechanism for long-term pulsations of very hot and luminous stars. These involve the interplay between convection, radiation, atmospheric clumping and winds, which collectively feed back to stellar expansion and contraction. We discuss these ideas and point out the future work required in order to fill in the blanks.
We present the first physical characterization of the young open cluster VVVCL041. We spectroscopically observed the cluster main-sequence stellar population and a very-massive star candidate: WR62-2. CMFGEN modelling to our near-infrared spectra indicates that WR62-2 is a very luminous (10^6.4±0.2 L⊙)and massive (∼ 80M⊙) star.
We present results from our near-infrared spectroscopy with VLT/ISAAC of four, massive eclipsing binary systems in the young, heavily reddened, massive Danks clusters. We derive accurate fundamental parameters and the distance to these massive systems, which comprise of OIf+, WR and O-type stars. Our goal is to increase the sample of well-studied WR stars and constrain their physics by comparison with evolutionary models.
Für Margot Faak (1926–2015)
Am 14. Juni 2015 starb unsere Kollegin Margot Faak im 89. Lebensjahr. Wir erinnern an sie mit Worten des Abschieds von Eberhard Knobloch und dem Wiederabdruck eines Aufsatzes aus ihrer Feder von 1999.
Die Neuveröffentlichung erfolgt mit freundlicher Genehmigung der Alexander von Humboldt-Stiftung.
Der Text wurde in den Fußnoten durch einige aktuelle bibliographische und sachliche Angaben ergänzt.
HiN VII, 13 (2006) war Margot Faak zu ihrem 80. Geburtstag gewidmet. Das Heft enthält einen Lebenslauf und ein Verzeichnis ihrer Schriften.
Berlin, Oktober 2015
Regina Mikosch und Ingo Schwarz
When it comes to footnotes, Alexander von Humboldt was ahead of his times even though his references leave much to be desired by today’s academic standards. This article examines the footnotes of Humboldt’s Essai politique sur l‘île de Cuba (1826). While it is not always easy to decipher his sometimes cryptic references, the undertaking is worthwhile: Humboldt’s footnotes do not only reveal his vast networks of knowledge. They also provide glimpses of ongoing, contemporary disputes among different scholars that involve Humboldt’s writings. They also present Humboldt’s reactions to such disputes. Exploring Humboldt’s footnotes consequently allows the reader to access both Humboldt the scholar and Humboldt the human being.
Die Studieneingangsphase stellt für Studierende eine Schlüsselphase des tertiären Ausbildungsabschnitts dar. Fachwissenschaftliches Wissen wird praxisfern vermittelt und die Studierenden können die Zusammenhänge zwischen den Themenfeldern der verschiedenen Vorlesungen nicht erkennen. Zur Verbesserung der Situation wurde ein Workshop entwickelt, der die Verbindung der Programmierung und der Datenstrukturen vertieft. Dabei wird das Spiel Go-Moku1 als Android-App von den Studierenden selbständig entwickelt. Die Kombination aus Software (Java, Android-SDK) und Hardware (Tablet-Computer) für ein kleines realistisches Softwareprojekt stellt für die Studierenden eine neue Erfahrung dar.
Erstsemester-Studierende sind mit den Anforderungen des Lehr-/ Lernprozess einer Universität oder Fachhochschule noch nicht vertraut. Ihre Erwartungen orientieren sich vielmehr an ihrer bisherigen Lerngeschichte (Abitur, Fachabitur, o. ä.). Neben den fachlichen Anforderungen des ersten Semesters müssen die Studierenden also auch Veränderungen im Lehr-/Lernprozess erkennen und bewältigen. Es wird anhand einer Output-orientierten
informatischen Lehrveranstaltung aufgezeigt, dass sich aus deren strengen Anforderungen der Messbarkeit klare Kompetenzbeschreibungen ergeben, die besonders dem Orientierungsbedürfnis Erstsemester-Studierender entgegenkommen.
Lo pintoresco se puede definir como un sentimiento que invita al espectador de una escena particular a reproducirla en un cuadro, algo que permitió a los viajeros del siglo XIX transportar las imágenes como posesiones, especialmente a través de la publicación de un Atlas Pittoresque. Cada una de esas imágenes es un testimonio de los viajes y sus historias cruzadas. Este es el caso de la lámina III, Vista de la Plaza Mayor de México, que forma parte de la obra Vues des Cordillères et Monuments des Peuples Indigènes de l’Amérique, una imagen que ilustra las redes de intercambio que se sucedían entre artistas y científicos a través de los viajes y expediciones.
En este breve ensayo propongo que en la ascensión al Teide Alexander von Humboldt pudo adquirir una perspectiva integral, que le sirvió como marco de comunicación científica para aunar la multitud de datos que se había dispuesto a recoger en su breve estancia en la isla. Más aun, de ahí en adelante este marco además le serviría para darle sentido de conjunto a las incontables y diversas informaciones que recogería en los restantes cinco años de viaje. Para poner en evidencia el enfoque de la visita a Tenerife de Humboldt, analizo su relato de la ascensión al Teide suponiendo que está estructurado según los relatos de viajes épicos y peregrinaciones.
In this paper we describe the recent state of our research
project concerning computer science teachers’ knowledge on students’
cognition. We did a comprehensive analysis of textbooks, curricula
and other resources, which give teachers guidance to formulate assignments.
In comparison to other subjects there are only a few concepts
and strategies taught to prospective computer science teachers in university.
We summarize them and given an overview on our empirical
approach to measure this knowledge.
Así que als Diskursmarker
(2015)
The present paper discusses Spanish así que (‘so that’) as a discourse marker by means of data that are retrieved from the Corpus del Español. The synchronic study has both a quantitative and a qualitative side. From a quantitative perspective the use of así que as a discourse marker is compared with its use as a conjunction. It is shown that así que as a conjunction is far more frequent. The qualitative analysis focuses on the different procedural meanings of así que: it can be used to introduce a summary, a consequence or an inference, and, on behalf of the interlocutor, even a question. The study furthermore reveals that así que as a discourse marker can well be analysed in terms of adfunctionalization / capitalization, i.e. when an already existing means of expression becomes exploited for wider purposes. In this context, the notions of grammaticalization, lexicalization and pragmaticalization are also briefly discussed.
Es wird ein Informatik-Wettbewerb für Schülerinnen und Schüler der Sekundarstufe II beschrieben, der über mehrere Wochen möglichst realitätsnah die Arbeitswelt eines Informatikers vorstellt. Im Wettbewerb erarbeiten die Schülerteams eine Android-App und organisieren ihre Entwicklung durch Projektmanagementmethoden, die sich an professionellen, agilen Prozessen orientieren. Im Beitrag werden der theoretische Hintergrund zu Wettbewerben, die organisatorischen und didaktischen Entscheidung, eine erste Evaluation sowie Reflexion und Ausblick dargestellt.
Bericht über die Tätigkeit des Menschenrechtsausschusses der Vereinten Nationen im Jahre 2013
(2015)
Bericht über die Tätigkeit des Menschenrechtsausschusses der Vereinten Nationen im Jahre 2014
(2015)
Bewegte Systematik
(2015)
Die Amerikanischen Reisetagebücher stellen eine Herausforderung für die Erforschung historischer Epistemologie dar. Der vorliegende Aufsatz will ausgehend vom Scheitern einer eindeutigen gattungsgeschichtlichen Zuschreibung die Sonderstellung der Bände als Instrumente der Erfahrung herausarbeiten, welche an der Schwelle zum 19. Jh. den ontologischen Optimismus sowie das methodische Tasten eines Wissenschaftlers, Schriftstellers und Forschungsreisenden in subjektbezogener Form zugänglich machen. Gerade der multifunktionale Charakter der ‚Journale‘ als Log- bzw. Reisetagebücher und Skizzenhefte, die noch weit entfernt von der Ordnung wissenschaftlichen Schreibens scheinen, lassen jene Voraussetzungen wissenschaftlicher Erkenntnisprozesse sichtbar werden, mithilfe derer Humboldt innerhalb der kantschen Koordinaten Raum und Zeit einen ‚Rhythmus‘ situativ verarbeiteter Natur- und Welterfahrung in ein dynamisches Speichermedium einfließen lässt.
BugHunt
(2015)
Competencies related to operating systems and computer
security are usually taught systematically. In this paper we present
a different approach, in which students have to remove virus-like
behaviour on their respective computers, which has been induced by
software developed for this purpose. They have to develop appropriate
problem-solving strategies and thereby explore essential elements of
the operating system. The approach was implemented exemplarily in
two computer science courses at a regional general upper secondary
school and showed great motivation and interest in the participating
students.
The paper presents two approaches to the development of
a Computer Science Competence Model for the needs of curriculum
development and evaluation in Higher Education. A normativetheoretical
approach is based on the AKT and ACM/IEEE curriculum
and will be used within the recommendations of the German
Informatics Society (GI) for the design of CS curricula. An empirically
oriented approach refines the categories of the first one with regard to
specific subject areas by conducting content analysis on CS curricula of
important universities from several countries. The refined model will be
used for the needs of students’ e-assessment and subsequent affirmative
action of the CS departments.
Computational Thinking
(2015)
Digital technology has radically changed the way people
work in industry, finance, services, media and commerce. Informatics
has contributed to the scientific and technological development of our
society in general and to the digital revolution in particular. Computational
thinking is the term indicating the key ideas of this discipline that
might be included in the key competencies underlying the curriculum
of compulsory education. The educational potential of informatics has
a history dating back to the sixties. In this article, we briefly revisit this
history looking for lessons learned. In particular, we focus on experiences
of teaching and learning programming. However, computational
thinking is more than coding. It is a way of thinking and practicing interactive
dynamic modeling with computers. We advocate that learners
can practice computational thinking in playful contexts where they can
develop personal projects, for example building videogames and/or robots,
share and discuss their construction with others. In our view, this
approach allows an integration of computational thinking in the K-12
curriculum across disciplines.
Concluding Remarks
(2015)
This paper originated from discussions about the need for
important changes in the curriculum for Computing including two focus
group meetings at IFIP conferences over the last two years. The
paper examines how recent developments in curriculum, together with
insights from curriculum thinking in other subject areas, especially mathematics
and science, can inform curriculum design for Computing.
The analysis presented in the paper provides insights into the complexity
of curriculum design as well as identifying important constraints and
considerations for the ongoing development of a vision and framework
for a Computing curriculum.
Der andere Weg zur Wahrheit
(2015)
Vorliegender Aufsatz befasst sich mit der Auseinandersetzung des Philosophen Franz Rosenzweig mit der Jesus-Figur. Dabei werden zwei Texte Rosenzweigs in den Blick genommen: „Atheistische Theologie“ (1914) und „Der Stern der Erlösung“ (1921). Hinzu kommen der Briefwechsel, den er mit Margrit und Eugen Rosenstock zwischen 1917 und 1929 führt und ein Text von Eduard Strauß, den letzterer im Rahmen seiner Tätigkeit im Frankfurter Jüdischen Lehrhaus entworfen hat. Durch diese Texte wird gezeigt, wie die Analyse der Jesus-Figur zur Auseinandersetzung mit seiner Historisierung durch die protestantische Theologie wird. Neben Rosenzweig, Buber und Strauß tragen weitere jüdische Gelehrte zu dieser Debatte bei. Diese Debatten um die Geschichtlichkeit Jesu werden auch in den Kontext des Verhältnisses zwischen Christentum und Judentum und ferner in Rosenzweigs Bemühungen um einen christlichjüdischen Dialog eingebettet.
Der kurze Aufsatz gibt einen Überblick über den erhaltenen Briefwechsel zwischen A. v. Humboldt und Charles Lyell. Er veröffentlicht darüber hinaus einen undatierten, bisher unbekannten Brief Humboldts an Lyell. Der Brief kann mit Hilfe eines Briefes an Pertz datiert werden. Deshalb wird auch dieser Brief zum ersten Mal vollständig veröffentlicht.
In diesem Beitrag soll es darum gehen, anhand der Distinktion von Jetztzeit und Erinnerung scheinbare Einheiten im lyrischen Werk der Nelly Sachs zu hinterfragen. Ein Nexus der Jesusfigur zur Shoah ist in den Gedichten nicht zu übersehen; inwieweit eine Korrelation beider Diskurse zwischen dem perennierenden Leiden der Opfer und dem am Kreuz Gemarterten besteht, ist der Gegenstand dieser Untersuchung. Jesus wird im lyrischen Oeuvre auf der zeitlichen wie inhaltlichen Ebene neu figuriert: nicht als christologisch-dogmatische Erlöserfigur, sondern als der qualvoll gemarterte Mann, dessen Schrei im 20. Jahrhundert eine neue Lesbarkeit generiert: als leidender Mit-Bruder. Der historische Index der Jesus-Gestalt wird in der Passionsszenerie, die jedoch transformativ modifiziert wird, manifest.
Detection and Characterization of Wolf-Rayet stars in M81 with GTC/OSIRIS spectra and HST images
(2015)
Here we investigate a sample of young star clusters (YSCs) and other regions of recent star formation with Wolf-Rayet (W-R) features detected in the relatively nearby spiral galaxy M81 by analysing long-slit (LS) and Multi-Object Spectroscopy (MOS) spectra obtained with the OSIRIS instrument at the 10.4-m Gran Telescopio Canarias (GTC). We take advantage of the synergy between GTC spectra and Hubble Space Telescope (HST) images to also reveal their spatial localization and the environments hosting these stars. We finally discuss and comment on the next steps of our study.
Die Reisetagebücher der Amerika-Reise (1799-1804) stellen ein Kompendium an schriftlichen Einträgen, Tabellen, Diagrammen und Zeichnungen dar, das in der Tradition römischer Papiermuseen des 17. Jhs. steht. Sie können als Mikrokosmen kleiner Kunstkammern aufgefasst werden, in denen Naturobjekte, Kunstwerke und Arbeitsmittel einen gemeinsamen Reflexionsraum bilden. Im Zentrum des vorliegenden Beitrags steht Humboldts Auffassung einer gestalteten Bestimmung von Landschaft vermittels besonders einprägsamer Bildformen. Auf erstaunliche Weise nähert sich Humboldts Ästhetik der Gesamtsicht von Natur Charles Darwins Begriff der natürlichen Schönheit an. In den Reisetagebüchern zeigt sich ein heterogener, von Lebendigkeit zeugender Charakter, der sowohl durch das unterschiedliche Format der einzelnen Hefte, als auch durch die inkonsistente Behandlung des Papiers erreicht wird. Dieser bewegliche Zug setzt sich in zahlreichen Zetteln, Briefen und weiteren Texten fort als ein eigenes Prinzip von Evolution.
For the calculation of the work in an irreversible pressure-volume change, we propose approxima-tions, which in contrast to the usual representation in the literature reflect the work performed during expansion and compression symmetrically. The calculations are based on the Reversible-Share-Theorem: Is used the force to overcome for calculating the work, so it captures only the configurational reversible work share.
Die Arbeitswelt im Fokus
(2015)
Für Bachelor-Studierende der Wirtschaftsinformatik im zweiten Semester an der Fachhochschule Kiel werden im Modul Informationsmanagement neben klassischen didaktischen Ansätzen in einer seminaristischen Unterrichtsform so genannte „Aktivbausteine“ eingesetzt: Studierende erhalten zum einen die Gelegenheit, sich im Kontakt mit Fach- und Führungskräften aus der Industrie ein konkretes Bild vom Beruf der Wirtschaftsinformatikerin bzw. des Wirtschaftsinformatikers zu machen; zum anderen erarbeiten sie innovative Ansätze der Prozessverbesserung aus Sicht der IT oder mit Nutzenpotenzial für die IT und präsentieren ihre Ergebnisse öffentlich im Rahmen des Kieler Prozessmanagementforums. Diese Aktivbausteine dienen insbesondere der Berufsfeldorientierung: Durch die Informationen, die die Studierenden über die Anforderungen und Tätigkeiten von im Beruf stehenden Menschen erhalten, werden sie in die Lage versetzt, fundierte Entscheidungen bzgl. ihrer Studiengestaltung und Berufswahl zu treffen. Im Beitrag wird die Konzeption der Bausteine vorgestellt und deren Grad der Zielerreichung durch aktuelle Evaluationsergebnisse erläutert. Zudem wird die motivationale Wirkung der Aktivbausteine anhand der Theorie der Selbstbestimmung von Deci und Ryan [DR1985, DR1993, DR2004] erläutert.
I. Gründung, Aufgaben und Struktur des Hochkommissariats
II. Zur Rolle des OHCHR im und gegenüber dem Menschenrechtsrat
III. Zu Erfolgschancen von Feldmissionen in eher schwierigen Ländern: China, Russische Föderation, Afghanistan, Sudan und Kolumbien
IV. Zur Frage der politischen Unabhängigkeit des OHCHR
V. Schlussfolgerungen und Ausblick
We discuss our most recent findings on the diffuse X-ray emission within Wolf-Rayet (WR) nebulae. The best-quality X-ray observations of these objects are those performed by XMM- Newton and Chandra towards S 308, NGC 2359, and NGC 6888. Even though these three WR nebulae might have different formation scenarios, they all share similar characteristics: i) the main plasma temperatures of the X-ray-emitting gas is found to be T =[1–2]×^K, ii) the diffuse X-ray emission is confined inside the [O iii] shell, and iii) their X-ray luminosities and electron densities in the 0.3–2.0 keV energy range are LX ≈10^33–10^34 erg s-1 and ne ≈0.1–1 cm^-3 . These properties and the nebular-like abundances of the hot gas suggest mixing and/or thermal conduction is taking an important rôle reducing the temperature of the hot bubble.
Participants of this workshop will be confronted exemplarily
with a considerable inconsistency of global Informatics education at
lower secondary level. More importantly, they are invited to contribute
actively on this issue in form of short case studies of their countries.
Until now, very few countries have been successful in implementing
Informatics or Computing at primary and lower secondary level. The
spectrum from digital literacy to informatics, particularly as a discipline
in its own right, has not really achieved a breakthrough and seems to
be underrepresented for these age groups. The goal of this workshop
is not only to discuss the anamnesis and diagnosis of this fragmented
field, but also to discuss and suggest viable forms of therapy in form of
setting educational standards. Making visible good practices in some
countries and comparing successful approaches are rewarding tasks for
this workshop.
Discussing and defining common educational standards on a transcontinental
level for the age group of 14 to 15 years old students in a readable,
assessable and acceptable form should keep the participants of this
workshop active beyond the limited time at the workshop.
The evolution of massive stars is strongly influenced by their initial chemical composition. We have computed rapidly-rotating massive star models with low metallicity (∼1/50 Z⊙) that evolve chemically homogeneously and have optically-thin winds during the main sequence evolution. These luminous and hot stars are predicted to emit intense mid- and far-UV radiation, but without the broad emission lines that characterize WR stars with optically-thick winds. We show that such Transparent Wind UV-Intense (TWUIN) stars may be responsible for the high number of He ii ionizing photons observed in metal-poor dwarf galaxies, such as IZw 18. We find that these TWUIN stars are possible long-duration gamma-ray burst progenitors.
Carbon-rich Wolf-Rayet stars are efficient carbon dust makers. Despite the strong evidence for dust formation in these objects provided by infrared thermal emission from dust, the routes to nucleation and condensation and the physical conditions required for dust production are still poorly understood. We discuss here the potential routes to carbon dust and the possible locations conducive to dust formation in the colliding winds of WC binaries.
E-Learning
(2015)
Zusammenfassung – nichtamtliche Leitsätze:
• Ein allgemeines Burkaverbot in der Öffentlichkeit verstößt nicht gegen Art. 8 oder 9
EMRK.
• Das Tragen einer Burka unterfällt als private Lebensführung dem Schutzbereich des
Art. 8 EMRK sowie als Religionsausübung dem Schutzbereich des Art. 9 EMRK.
• Ein allgemeines Burkaverbot in der Öffentlichkeit zum Schutz der Sicherheit verfolgt
ein legitimes Ziel, ist in Ermangelung einer allgemeinen Gefahr aber nicht erforderlich
und damit unverhältnismäßig.
• Der Schutz des Respekts für die Gleichheit von Mann und Frau oder für die Menschenwürde
lässt sich nicht als legitimes Ziel für ein Burkaverbot heranziehen.
• Der Schutz des Respekts für die Minimalbedingungen gesellschaftlichen Zusammenlebens
stellt ein legitimes Ziel für ein Burkaverbot dar. Das Burkaverbot ist angesichts
des breiten staatlichen Ermessensspielraums in einer solchen Frage nicht unverhältnismäßig.
Einführung
(2015)
It has been observed for many African languages that focussed subjects
have to appear outside of their syntactic base position, as opposed to
focussed objects, which can remain in-situ. This is known as subjectobject
asymmetry of focus marking, which Fiedler et al. (2010) claim
to hold also for Akan. Genzel (2013), on the other hand, argues that
Akan does not exhibit a subject-object focus asymmetry. A questionnaire
study and a production experiment were carried out to investigate
whether focussed subjects may indeed be realized in-situ in Akan. The
results suggest that (i) focussed subjects do not have to be obligatorily
realized ex-situ, and that (ii) the syntactic preference for the realization
of a focussed subject highly depends on exhaustivity.
Massive, luminous stars reaching the Eddington limit in their interiors develop very dilute, extended envelopes. This effect is called envelope inflation. If the progenitors of Type Ib/c supernovae, which are believed to be Wolf-Rayet (WR) stars, have inflated envelopes then the shock breakout signals diffuse in them and can extend their rise times significantly. We show that our inflated, hydrogen-free, WR stellar models with a radius of ∼R⊙ can have shock breakout signals longer than ∼ 60 s. The puzzlingly long shock breakout signal observed in the Type Ib SN 2008D can be explained by an inflated progenitor envelope, and more such events might argue in favour of existence of inflated envelopes in general.
We an optically-thick, transonic, steady wind model for a H-free Wolf-Rayet star. A bifurcation is found across a critical mass loss rate Mb. Slower winds M < Mb extend by several hydrostatic stellar radii, reproduce features of envelope in ation from Petrovic et al. (2006) and Gräfener et al. (2012), and are energetically unbound. This work is of particular interest for extended envelopes and winds, radiative hydrodynamic instabilities (eg. wind stagnation, clumping, etc.), and NLTE atmospheric models.
Eta Carinae
(2015)
Since Augusto Damineli's demonstration in 1996 that Eta Carinae is a binary with a 5.52 year period, many innovative observations and increasingly advanced three-dimensional models have led to considerable insight on this massive system that ejected at least ten, possibly forty, solar masses in the nineteenth century. Here we present a review of our current understanding of this complex system and point out continuing puzzles.
Der folgende Artikel beschreibt die Evaluation eines Lehrvideos zum informatischen Problemlösen, welches auf der Grundlage einer Vergleichsstudie mit starken und schwachen Problemlösern entwickelt wurde. Beispielhaft wird in dem Film ein Färbeproblem durch einen fiktiven Hochleister unter lautem Denken gelöst, die einzelnen Arbeitsschritte werden abschnittsweise kommentiert und erklärt. Ob dieses Lernkonzept von Studenten akzeptiert wird und sich durch Anschauen des Videos tatsächlich ein Lerneffekt einstellt, wurde durch eine Befragung und eine erste Vergleichsstudie untersucht.
Wolf-Rayet stars are important sources for the enrichment of the ISM with nuclear processed elements, UV photons and momentum. They are descendants of high-mass stars for which short lifetimes and transition times can hamper the spectral classification of the stars in their different evolutionary phases. The expanded stellar atmospheres of Wolf-Rayet stars can show spectra which seem inconsistent with the anticipated underlying evolution phase, for example in late hydrogen-burning WN stars and Of/WN transition stars. We present a sequence of synthetic spectra of the Potsdam Wolf-Rayet models based on the latest Geneva stellar evolution models. This will visualize the changes in stellar spectra over a full stellar lifetime. Direct comparison with observed stellar spectra, as well as the evolution of diagnostic line ratios will improve the connection of spectral classification and evolution phase.
This paper reopens the discussion on focus marking in Akan (Kwa,
Niger-Congo) by examining the semantics of the so-called focus marker
in the language. It is shown that the so-called focus marker expresses
exhaustivity when it occurs in a sentence with narrow focus. The study
employs four standard tests for exhaustivity proposed in the literature
to examine the semantics of Akan focus constructions (Szabolsci 1981,
1994; É. Kiss 1998; Hartmann and Zimmermann 2007). It is shown that
although a focused entity with the so-called focus marker nà is
interpreted to mean ‘only X and nothing/nobody else,’ this meaning
appears to be pragmatic.
In the project MoKoM, which is funded by the German
Research Foundation (DFG) from 2008 to 2012, a test instrument
measuring students’ competences in computer science was developed.
This paper presents the results of an expert rating of the levels of
students’ competences done for the items of the instrument.
At first we will describe the difficulty-relevant features that were
used for the evaluation. These were deduced from computer science,
psychological and didactical findings and resources. Potentials and
desiderata of this research method are discussed further on. Finally
we will present our conclusions on the results and give an outlook on
further steps.
The super massive binary system, η Car, experienced periastron passage in the summer of 2014. We observed the star twice around the maximum (forb =0.97, 2014 June 6) and just before the minimum (ϕorb =0.99, 2014 July 28) of its wind-wind colliding (WWC) X-ray emis-sion using the XMM-Newton and NuSTAR observatories, the latter of which is equipped with extremely hard X-ray (>10 keV) focusing mirrors. In both observations, NuSTAR detected the thermal X-ray tail up to 40-50 keV. The hard slope is consistent with an electron tem- perature of ∼6 keV, which is significantly higher than the ionization temperature (kT ∼4 keV) measured from the Fe K emission lines, assuming collisional equilibrium plasma. The spectrum did not show a hard power-law component above this energy range, unlike earlier detections with INTEGRAL and Suzaku. In the second NuSTAR observation, the X-ray flux above 5 keV declined gradually in ∼1 day. This result suggests that the WWC apex was gradually hidden behind the optically thick primary wind around conjunction.
Luminous Blue Variables (LBVs) are stars is a transitional phase massive stars may enter while evolving from main-sequence to Wolf-Rayet stars. The to LBVs intrinsic photometric variability is based on the modulation of the stellar spectrum. Within a few years the spectrum shifts from OB to AF type and back. During their cool phase LBVs are close to the Humphreys-Davidson (equivalent to Eddington/Omega-Gamma) limit. LBVs have a rather high mass loss rate, with stellar winds that are fast in the hot and slower in the cool phase of an LBV. These alternating wind velocities lead to the formation of LBV nebulae by wind-wind interactions. A nebula can also be formed in a spontaneous giant eruption in which larger amounts of mass are ejected. LBV nebulae are generally small (< 5 pc) mainly gaseous circumstellar nebulae, with a rather large fraction of LBV nebulae being bipolar. After the LBV phase the star will turn into a Wolf-Rayet star, but note that not all WR stars need to have passed the LBV phase. Some follow from the RSG and the most massive directly from the MS phase. In general WRs have a large mass loss and really fast stellar winds. The WR wind may interact with winds of earlier phases (MS, RSG) to form WR nebulae. As for WR with LBV progenitors the scenario might be different, here no older wind is present but an LBV nebula! The nature of WR nebulae are therefore manifold and in particular the connection (or family ties) of WR to LBV nebulae is important to understand the transition between these two phases, the evolution of massive stars, their winds, wind-wind and wind-nebula interactions. Looking at the similarities and differences of LBV and WR nebula, figuring what is a genuine LBV and WR nebula are the basic question addressed in the analysis presented here.
Obtaining a complete census of massive, evolved stars in a galaxy would be a key ingredient for testing stellar evolution models. However, as the evolution of stars is also strongly dependent on their metallicity, it is inevitable to have this kind of data for a variety of galaxies with different metallicities. Between 2009 and 2011, we conducted the Magellanic Clouds Massive Stars and Feedback Survey (MSCF); a spatially complete, multi-epoch, broad- and narrow-band optical imaging survey of the Large and Small Magellanic Clouds. With the inclusion of shallow images, we are able to give a complete photometric catalog of stars between B ≈ 18 and B ≈ 19 mag.
These observations were augmented with additional photometric data of similar spatial res-
olution from UV to IR (e.g. from GALEX, 2MASS and Spitzer) in order to sample a large portion of the spectral energy distribution of the brightest stars (B < 16 mag) in the Magel- lanic Clouds. Using these data, were are able to train a machine learning algorithm that gives us a good estimate of the spectral type of tens of thousands of stars.
This method can be applied to the search for Wolf-Rayet-Stars to obtain a sample of candi- dates for follow-up observations. As this approach can, in principle, be adopted for any resolved galaxy as long as sufficient photometric data is available, it can form an effective alternative method to the classical strategies (e.g. He II filter imaging).
We summarize past and current surveys for WRs among the Local Group galaxies, empha- sizing both the why and how. Such studies are invaluable for helping us learn about massive star evolution, and for providing sensitive tests of the stellar evolution models. But for such surveys to be useful, the completeness limits must be well understood. We illustrate that point by following the “evolution” of the observed WC/WN ratio in nearby galaxies. We end by examining our new survey for WR stars in the Magellanic Clouds, which has revealed a new type of WN star, never before seen.
The total population of Wolf-Rayet (WR) stars in the Galaxy is predicted by models to be as many as ~6000 stars, and yet the number of catalogued WR stars as a result of optical surveys was far lower than this (~200) at the turn of this century. When beginning our WR searches using infrared techniques it was not clear whether WR number predictions were too optimistic or whether there was more hidden behind interstellar and circumstellar extinction. During the last decade we pioneered a technique of exploiting the near- and mid-infrared continuum colours for individual point sources provided by large-format surveys of the Galaxy, including 2MASS and Spitzer/GLIMPSE, to pierce through the dust and reveal newly discovered WR stars throughout the Galactic Plane. The key item to the colour discrimination is via the characteristic infrared spectral index produced by the strong winds of the WR stars, combined with dust extinction, which place WR stars in a relatively depopulated area of infrared colour-colour diagrams. The use of the Spitzer/GLIMPSE 8µm and, more recently, WISE 22µm fluxes together with cross-referencing with X-ray measurements in selected Galactic regions have enabled improved candidate lists that increased our confirmation success rate, achieved via follow-up infrared and optical spectroscopy. To date a total of 102 new WR stars have been found with many more
candidates still available for follow-up. This constitutes an addition of ~16% to the current
inventory of 642 Galactic WR stars. In this talk we review our methods and provide some
new results and a preliminary review of their stellar and interstellar medium environments. We provide a roadmap for the future of this search, including statistical modeling, and what we can add to star formation and high mass star evolution studies.
Foreign Accent Syndrome
(2015)
The gas cloud G2 is currently being tidally disrupted by the Galactic Centre super-massive black hole, Sgr A*. The region around the black hole is populated by ∼ 30 Wolf-Rayet stars, which produce strong outflows. Here we explore the possibility that gas clumps like G2 originate from the collision of stellar winds via the non-linear thin shell instability.
Der Beitrag stellt das Konzept des Semantischen Positionierens als eine Möglichkeit vor, Grundformen des wissenschaftlichen Arbeitens und elementare Formen der diskursiven Auseinandersetzung zu vermitteln, ohne dass die Studierenden sich inhaltlich an der aktuellen Forschung beteiligen müssten. Die Umsetzung dieses Konzepts im Bachelorstudium der Informatik verdeutlicht, dass mit diesem Ansatz sowohl die Kompetenzen für den Übergang in den mehr forschungsgetriebenen Masterstudiengang als auch für die berufliche Wissensarbeit erworben werden können.
Frontale Präsenz
(2015)
Ein bislang unveröffentlichtes Porträt Alexander von Humboldts aus der Hand Frédéric d’Houdetots, ein Schüler des Malers Jacques-Louis David, bereichert die Humboldt-Ikonographie um eine Darstellung, die den berühmten Reisenden und Gelehrten als jungen Mann, wenige Jahre nach seiner Rückkehr aus Amerika zeigt – beeindruckend lebendig, fokussiert und präsent. Das 1807 während der Franzosenzeit in Berlin entstandene Porträt verweist als Teil eines im Conseil d’État in Paris aufbewahrten Porträt-Albums auf die Zirkel und Beziehungen, die sich in der besetzten preußischen Hauptstadt zwischen Besatzern, jüdischen Salonkreisen und der wissenschaftlichen Community gebildet haben, ein Nährboden für den transnationalen Austausch von Vertretern einer jungen und vitalen Generation, die sich als echte Europäer verstanden.
Although we all use the name Wolf-Rayet to refer to specific groups of stars, “Wolf-Rayet” per se is really an astrophysical phenomenon of fast-moving, hot plasma, normally expanding around a hot star. However, expediency demands that we follow established traditions by referring to three specific kinds of WR stars: (1) cWR, “classical” He-burning descendants of massive, O-type stars, presumably all of which pass through a WR stage; (2) WNh, the most massive and luminous hydrogen-rich main-sequence stars with strong winds; and (3) [WR], the central stars of some 15 % of Planetary Nebulae. Wolf-Rayet stars are the epitome of relatively stable stars with the highest mass-loss rates for their kind. It behooves us to understand the what, how and why of this circumstance, along with its manyfold and fascinating consequences.
HD5980
(2015)
HD5980 is a multiple system containing at least 3 very massive and luminous stars. Located in the Small Magellanic Cloud, it is an ideal system for studying the massive star structure and evolutionary processes in low-metallicity environments. Intensely observed over the past few decades, HD5980 is a treasure trove of information on stellar wind structure, on wind-wind collisions and on the formation of wind-blown circumstellar structures. In addition, its characteristics suggest that the eclipsing WR+LBV stars of the system are the product of quasihomogeneous chemical evolution, thus making them candidate pair production supernovae or GRB progenitors. This paper summarizes some of the outstanding results derived from half a century of observations and recent theoretical studies.
Helium stars
(2015)
There are outstanding problems in trying to reproduce the observed nature of Wolf–Rayet stars from theoretical stellar models. We have investigated the effects of uncertainties, such as composition and mass-loss rate, on the evolution and structure of Wolf–Rayet stars and their lower mass brethren. We find that the normal Conti scenario needs to be altered, with different WR types being due to different initial masses as well as different stages of evolution.
As WR 6 is a putatively single WN4 star, and is relatively bright (V = 6.9), it is an ideal case for studying the wind mechanisms in these extremely luminous stars. To obtain higher resolution spectra at higher energy (above 1 keV) than previously obtained with the XMM/Newton RGS, we have observed WR 6 with the Chandra High Energy Transmission Grating Spectrometer for 450 ks. We have resolved emission lines of S, Si, Mg, Ne, and Fe, which all show a “fin"-shaped prole, characteristic of a self-absorbed uniformly expanding shell. Steep blue edges gives robust maximal expansion velocities of about 2000 km/s, somewhat larger than the 1700km/s derived from UV lines. The He-like lines all indicate that X-ray emitting plasmas are far from the photosphere – even at the higher energies where opacity is lowest { as was also the case for the longer wavelength lines observed with XMM-Newton/RGS. Abundances determined from X-ray spectral modeling indicate enhancements consistent with nucleosynthesis. The star was also variable in X-rays and in simultaneous optical photometry obtained with Chandra aspect camera, but not coherently with the optically known period of 3.765 days.
How does the Implementation of a Literacy Learning Tool Kit influence Literacy Skill Acquisition?
(2015)
This study aimed at following how teachers transfer skills
into results while using ABRA literacy software. This was done in
the second part of the pilot study whose aim was to provide equity to
control group teachers and students by exposing them to the ABRACADABRA
treatment after the end of phase 1. This opportunity was
used to follow the phase 1 teachers to see how the skills learned were
being transformed into results. A standard three-day initial training and
planning session on how to use ABRA to teach literacy was held at the
beginning of each phase for ABRA teachers (phase 1 experimental and
phase 2 delayed ABRA). Teachers were provided with teaching materials
including a tentative ABRA curriculum developed to align with the
Kenyan English Language requirements for year 1 and 3 students. Results
showed that although there was no significant difference between
the groups in vocabulary-related subscales which include word reading
and meaning as well as sentence comprehension, students in ABRACADABRA
classes improved their scores at a significantly higher rate
than students in control classes in comprehension related scores. An
average student in the ABRACADABRA group improved by 12 and
16 percentile points respectively compared to their counterparts in the
control group.
How Things Work
(2015)
Recognizing and defining functionality is a key competence
adopted in all kinds of programming projects. This study investigates
how far students without specific informatics training are able to identify
and verbalize functions and parameters. It presents observations
from classroom activities on functional modeling in high school chemistry
lessons with altogether 154 students. Finally it discusses the potential
of functional modelling to improve the comprehension of scientific
content.
Humboldts Hefte
(2015)
Der 2013 geglückte Ankauf der Amerikanischen Tagebücher durch ein Konsortium öffentlicher und privater Geldgeber hat es nicht nur ermöglicht, Alexander von Humboldts Reisemanuskripte zum ersten Mal einer breiten interessierten Öffentlichkeit vorzustellen, sondern wirft auch ein besonderer Licht auf die Geschichte ihrer Rezeption und Erforschung. Welche Phasen der Arbeit und Auswertung der Tagebücher lassen sich nachzeichnen? Und an welchem Punkt steht die Humboldt-Forschung in dieser Frage heute?
Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray flux is tied to the orbital phase, and is a direct probe of the winds’ properties. In the Galactic center, ~30 WRs orbit the super massive black hole (SMBH) within ~10”, leading to a smorgasbord of wind-wind collisions. To model the X-ray emission of WR 140 and the Galactic center, we perform 3D hydrodynamic simulations to trace the complex gaseous flows, and then carry out 3D radiative transfer calculations to compute the variable X-ray spectra. The model WR 140 RXTE light curve matches the data well for all phases except the X-ray minimum associated with periastron, while the model spectra agree with the RXTE hardness ratio and the shape of the Suzaku observations throughout the orbit. The Galactic center model of the Chandra flux and spectral shape match well in the region r ≤ 3”, but the model flux falls off too rapidly beyond this radius.
In the last decades, stellar atmosphere codes have become a key tool in understanding massive stars, including precise calculations of stellar and wind parameters, such as temperature, massloss rate, and terminal wind velocity. Nevertheless, for these models the hydrodynamic equation is not solved in the wind. Motivated by the results of the CAK theory, the models typically use a beta velocity law, which however turns out not to be adequate for stars with very strong winds, and treat the mass-loss rate as a free parameter. In a new branch of the Potsdam Wolf-Rayet model atmosphere (PoWR) code, we solve the hydrodynamic equation consistently throughout the stellar atmosphere. The PoWR code performs the calculation of the radiative force without approximations (e.g. Sobolev). We show the impact of hydrodynamically consistent modelling on OB and WR stars in comparison to conventional models and discuss the obtained velocity fields and their impact on the observed spectral lines.
En las pinturas que retratan al erúdito Alexander von Humboldt encontramos densos signos visuales las cuales simbolizan su vida científica. La imagen del Chimborazo, cuya cima Humboldt no había alcanzado, recuerda la función epistémica de lo inacabado en su obra, mientras que la carta, el globo y su postura típica remiten al central significado del movimiento y al “escribir de cara a las cosas”. La presencia de sus objetos de escritura en las imagenes llama la atención, ya que se puede entender como referencia al significado de los diarios del viaje americano escritos durante toda la vida. En aquellos se ponen de manifiesto los momentos centrales del Humboldtian Science. El carácter del work in progress y la relacionalidad consecuente de la representación muestran las constantes epistemológicas de esta ciencia así como la dimensión de lo corporal en los manuscritos.
This paper discusses results from a small-scale research
study, together with some recently published research into student
perceptions of ICT for learning in schools, to consider relevant skills
that do not appear to currently being taught. The paper concludes by
raising three issues relating to learning with and through ICT that need
to be addressed in school curricula and classroom teaching.
The objectives of this study were to examine (a) the effect
of dynamic assessment (DA) in a 3D Immersive Virtual Reality
(IVR) environment as compared with computerized 2D and noncomputerized
(NC) situations on cognitive modifiability, and (b) the
transfer effects of these conditions on more difficult problem solving
administered two weeks later in a non-computerized environment. A
sample of 117 children aged 6:6-9:0 years were randomly assigned
into three experimental groups of DA conditions: 3D, 2D, and NC, and
one control group (C). All groups received the pre- and post-teaching
Analogies subtest of the Cognitive Modifiability Battery (CMB-AN).
The experimental groups received a teaching phase in conditions similar
to the pre-and post-teaching phases. The findings showed that cognitive
modifiability, in a 3D IVR, was distinctively higher than in the two
other experimental groups (2D computer group and NC group). It was
also found that the 3D group showed significantly higher performance
in transfer problems than the 2D and NC groups.
Before GAIA improves the HIPPARCOS survey, direct determination of the distance via parallax is only possible for γ Vel, but the analysis of the cluster or association to which WR stars are associated can give distances with a 50% to a 10% accuracy. The list of Galactic clusters, associations and clusters/association candidates has grown significantly in the last decade with the numerous deep, high resolution surveys of the Milky Way. In this work, we revisit the fundamental parameters of known clusters with WR stars, and we present the search for new ones. All our work is based on the catalogs from the VVV (from the VISTA telescope) and the UKIDS (from the UKIRT telescope) near infrared surveys. Finally, the relations between the fundamental parameters of clusters with WR stars are explored.
Der Erwerb der südamerikanischen Reisetagebücher Alexander von Humboldts durch die Staatsbibliothek Preußischer Kulturbesitz war 2014 ein bedeutendes Ereignis. In einem ersten Schritt wertet der Artikel unveröffentlichte Teile der Tagebücher und Dokumente aus dem Nachlass aus, um den „Kosmos Humboldt´scher Interessen“ zum Thema Pflanzengeographie zu umreißen, darunter auch seine Überlegungen zum Einfluss von Mensch und Tier auf die Ausbreitung von Pflanzen und die Veränderung von Vegetation. Die Einsichten des Gelehrten zur Abhängigkeit Europas von der sogenannten „Neuen Welt“ hinsichtlich der Nahrungsmittel werden ebenso behandelt. So vertrat Humboldt in seinen Ausführungen zum Thema „Was sind Barbaren?“ die These, dass Isolierung von Menschen aus der Gemeinschaft, Elend, Nahrungsmangel, klimatische Ursachen usw. „die Spuren von Zivilisation vertilgen“. Er betonte, dass es nötig sein, in einem weltweiten Wettstreit intellektueller Kräfte die Ressourcenknappheit zu überwinden.
The paper discusses the issue of supporting informatics
(computer science) education through competitions for lower and
upper secondary school students (8–19 years old). Competitions play
an important role for learners as a source of inspiration, innovation,
and attraction. Running contests in informatics for school students
for many years, we have noticed that the students consider the contest
experience very engaging and exciting as well as a learning experience.
A contest is an excellent instrument to involve students in problem
solving activities. An overview of infrastructure and development
of an informatics contest from international level to the national one
(the Bebras contest on informatics and computer fluency, originated
in Lithuania) is presented. The performance of Bebras contests in 23
countries during the last 10 years showed an unexpected and unusually
high acceptance by school students and teachers. Many thousands of
students participated and got a valuable input in addition to their regular
informatics lectures at school. In the paper, the main attention is paid
to the developed tasks and analysis of students’ task solving results in
Lithuania.