Die Aachener Thomas-Stahlforschung als kulturelles Kampffeld : Fritz Wüst, der Aachener Hütten-Aktien-Verein und die Forschungen der Technischen Hochschule Aachen zur Verbesserung des Thomas-Verfahrens 1901–1918

in Rasch, Manfred; Maas, Jacques (Eds.) Das Thomas-Verfahren in Europa. Entstehung – Entwicklung – Ende (2009)

Auf dem Feld der Thomas-Stahlforschung bestanden zwischen 1901 und 1918 besondere Voraussetzungen für eine enge Wechselwirkung zwischen der Technischen Hochschule Aachen und dem Aachener Hütten-Aktien ... [more ▼]

Auf dem Feld der Thomas-Stahlforschung bestanden zwischen 1901 und 1918 besondere Voraussetzungen für eine enge Wechselwirkung zwischen der Technischen Hochschule Aachen und dem Aachener Hütten-Aktien-Verein in Rothe Erde bei Aachen. Der 1901 nach Aachen berufene Professor Fritz Wüst betrieb mit Nachdruck die Verwissenschaftlichung der Eisenhüttenkunde. Zu seinem Programm gehörten experimentelle Feldstudien, Laborforschung und Theoriebildung. Das Hüttenwerk in Rothe Erde war bis 1918 einer der bedeutendsten deutschen Thomas-Stahlproduzenten. Die räumliche Nähe der beiden Institutionen und gute Kontakte des Betriebsdirektors Fritz Kintzlé zur Hochschule ließen eine fruchtbare Zusammenarbeit erwarten. Ein Blick auf die Beiträge des Aachener Eisenhüttenmännischen Instituts zur Verbesserung des Thomas-Verfahrens zeigt in der Folge jedoch ein anderes Bild. Zwar entstand 1907 mit der Doktorarbeit von Leo Laval eine wegweisende experimentelle Untersuchung des Thomas-Prozesses, jedoch resultierten daraus keine Impulse für weitergehende Forschungsvorhaben. Im Gegenteil – ausgehend von Lavals Arbeit, entwickelte Wüst die durchaus provokante These, dass das Thomas-Verfahren binnen kürze von den Herdfrischverfahren abgelöst werden würde. Dementsprechend fanden am Aachener Institut bis 1918 keine herausragenden Forschungen zum Thomas-Verfahren mehr statt. Zur Erklärung von Wüsts Haltung schließt der Beitrag mit der Deutung der Thomas-Stahlforschung als kulturelles Kampffeld im Sinne von Pierre Bourdieu. [less ▲]

AASA: locating the central administration of a subsidiary company which is part of a group of companies under Article 60 of Brussels I Regulation

in European Company Law (2015), 1

There is no definition of the term “central administration” under Article 60(1)(b) of Brussels I; and Article 60 of Brussels I does not make specific provisions for locating the central administration of ... [more ▼]

There is no definition of the term “central administration” under Article 60(1)(b) of Brussels I; and Article 60 of Brussels I does not make specific provisions for locating the central administration of a subsidiary company within a corporate group. English Courts in Anglo American South Africa Limited after a re-evaluation of the correctness of previous decisions by English judges on the subject of Article 60(1)(b), provided an autonomous interpretation of central administration, and sought to apply the concept of central administration in a “European way” to a subsidiary company within a corporate group. The author challenges the approach of English judges for not referring the question of how Article 60(1)(b) applies to corporate groups to the CJEU. [less ▲]

Ab initio approaches to Resonant Raman Spectroscopy of Transition Metal Dichalcogenides

Doctoral thesis (2017)

This thesis deals with the theory and simulation of resonant Raman spectroscopy in two-dimensional transition metal dichalcogenides. We present two different ab initio approaches. In the first, we ... [more ▼]

This thesis deals with the theory and simulation of resonant Raman spectroscopy in two-dimensional transition metal dichalcogenides. We present two different ab initio approaches. In the first, we calculate the Raman susceptibility tensor as a function of laser energy from the change of the dielectric susceptibility with atomic displacements. In the second, we formulate the Raman tensor in terms of time-dependent perturbation theory and calculate it using electron-light and electron-phonon coupling matrix elements obtained from density functional theory. We investigate the role of resonance, quantum interference and excitonic effects in the Raman spectra of single and triple-layer MoTe2. We compare our simulations with experimental results, explaining the dependence of the Raman intensities on the excitation energy. We demonstrate that the two approaches are formally and numerically equivalent in the adiabatic limit. In addition, the second approach allows to include the dynamical effects and captures a shift of the intensities with respect to the adiabatic case. This method is also more computationally efficient and is extended to include temperature effects using many-body perturbation theory. We have implemented both of these methods in a software package with interfaces to open source ab initio codes. Furthermore, we have developed web based tools to visualize excitonic states and phonon modes. [less ▲]

Ab initio calculations of the lattice dynamics of boron nitride nanotubes

in Physical Review B (2003), 68(4),

We present an extensive first-principles study of the phonons in boron nitride nanotubes using density functional perturbation theory in the local density approximation. Based on the nonsymmorphic rod ... [more ▼]

We present an extensive first-principles study of the phonons in boron nitride nanotubes using density functional perturbation theory in the local density approximation. Based on the nonsymmorphic rod-group symmetry of the tubes, the Raman- and infrared-active modes at the Gamma point of the one-dimensional Brillouin zone are evaluated. For zigzag and chiral nanotubes, the set of infrared-active modes is a subset of the Raman- active modes. In particular, the radial breathing mode is not only Raman but also infrared active. However, for armchair tubes, the sets of infrared-and Raman- active modes are disjoint. This may serve to spectroscopically distinguish between macroscopic samples of zigzag-chiral and armchair nanotubes. We present the frequencies of the active modes of zigzag, chiral, and armchair tubes as a function of the tube diameter and compare the results with the frequencies obtained by the zone-folding method, i.e., the rolling of a single hexagonal BN sheet into a tube. Except for the high-frequency tangential modes, the zone-folding results are in very good agreement with the ab initio calculations. The radial breathing mode frequency can be derived by folding a sheet of finite width. Finally, we show that the effects of bundling on the phonon frequencies are small. This demonstrates that the obtained results for isolated BN tubes may serve as a basis for an accurate assignment of phonon modes in spectroscopic measurements. [less ▲]

Ab initio perspective on the Mollwo-Ivey relation for F centers in alkali halides

in Physical Review. B: Condensed Matter and Materials Physics (2015), 92

We revisit the well-known Mollwo-Ivey relation that describes the ``universal'' dependence of the absorption energies of F-type color centers on the lattice constant a of alkali-halide crystals, E-abs ... [more ▼]

We revisit the well-known Mollwo-Ivey relation that describes the ``universal'' dependence of the absorption energies of F-type color centers on the lattice constant a of alkali-halide crystals, E-abs proportional to a(-n). We perform both state-of-the-art ab initio quantum chemistry and post-DFT calculations of F-center absorption spectra. By ``tuning'' independently the lattice constant and the atomic species we show that the scaling with the lattice constant alone 2 in agreement with the ``particle-in-the-box'' model. Keeping the lattice constant fixed and changing the atomic species enables us to quantify the ion-size effects which are shown to be responsible for the exponent n approximate to 1.8. [less ▲]

Ab-initio study of the temperature effects on the optical properties of transition metal dichalcogenides

Scientific Conference (2015, March 05)

The abbot and the Monastic Community in the Gaelic Churches, 550 to 800

in Glyn S. Burgess; Strijbosch, Clara (Eds.) The Brendan Legend. Texts and Versions (2006)

This chapters deals with aspects of the organisation of monastic communities in the Gaelic Churches from 550 to 800. It focusses on the role of the head of the community, the abbot, regarding general ... [more ▼]

This chapters deals with aspects of the organisation of monastic communities in the Gaelic Churches from 550 to 800. It focusses on the role of the head of the community, the abbot, regarding general questions of monastic discipline, organising of the liturgical life of the community, regulation of the diet and of the food provision in the community. [less ▲]

The ABCD of cyclic quadrilaterals

Article for general public (in press)

Abdications of Sovereignty in State Action and Horizontal Effect Jurisprudence

in Kahana, Tsvi; Scolnicov, Anat (Eds.) Boundaries of State, Boundaries of Rights: Human Rights, Private Actors, and Positive Obligations (2016)

This article argues that different regimes of horizontal effect adjudication invariably turn on different attitudes to state sovereignty. Aversions to horizontal effect are usually a reflection of an ... [more ▼]

This article argues that different regimes of horizontal effect adjudication invariably turn on different attitudes to state sovereignty. Aversions to horizontal effect are usually a reflection of an apprehension regarding state sovereignty (understood as a threat to liberty) whereas endorsements of horizonal effect usually reflect a positive regard for state sovereingty (as a condition for liberty). [less ▲]

Abel-Preis für Mathematiker Mischa Gromov

Article for general public (2009)