Cu NMR Study of Detwinned Single Crystals of Ortho--II YBCO6.5

Copper NMR has been used as a local probe of the oxygen ordering in Ortho--II YBa2Cu3O6.5 crystals grown in BaZrO3 crucibles. Line assignments have been made to each of the expected crystallographically inequivalent sites. The presence of distinct and narrow lines for these sites as well as the lack of a line known to be associated with oxygen defects indicates that these crystals are highly stoichiometric. Our estimate of the lower limit on the chain length is consistent with that derived from X-ray diffraction measurements. In addition, we have found no evidence for static magnetic moments, in contrast to some previous results.Comment: 11 pages, 7 figures, submitted to Physica

Coulomb gap in a model with finite charge transfer energy

The Coulomb gap in a donor-acceptor model with finite charge transfer energy $\Delta$ describing the electronic system on the dielectric side of the metal-insulator transition is investigated by means of computer simulations on two- and three-dimensional finite samples with a random distribution of equal amounts of donor and acceptor sites. Rigorous relations reflecting the symmetry of the model presented with respect to the exchange of donors and acceptors are derived. In the immediate neighborhood of the Fermi energy $\mu$ the the density of one-electron excitations $g(\epsilon)$ is determined solely by finite size effects and $g(\epsilon)$ further away from $\mu$ is described by an asymmetric power law with a non-universal exponent, depending on the parameter $\Delta$.Comment: 10 pages, 6 figures, submitted to Phys. Rev.

LOCAL PIEZOELECTRICITY IN SrTiO3-BiTiO3 CERAMICS

Local piezoelectric properties of Bi-doped SrTiO3 ceramics have been investigated by piezoresponse force microscopy. The appearance of both out-of-plane and in-plane polarization components confirmed the piezoelectric nature of the obtained signal. The absence of labyrinth-like structures in observed piezoelectric contrast is not consistent with the expected existence of a relaxor ferroelectric state in this material. The close similarity of local piezoelectric properties in Bi-doped SrTiO3 with pure SrTiO3 suggests that the origin of obtained piezoresponse can be attributed to the flexoelectric phenomenon. Bi-doping leads to occurrence of oxygen vacancies and negative charge on the surface of the sample

Two-photon parametric pumping versus two-photon absorption: A quantum jump approach

Published versio

Who stays proactive after entrepreneurship training? Need for cognition, personal initiative maintenance, and well-being

Personal initiative training is a promising way to increase entrepreneurial personal initiative, which is a key behavior for successful entrepreneurship. Although personal initiative training has been shown to promote personal initiative, little is known about how this proactive behavior can be maintained over time and what the consequences are. The training transfer literature suggests that training effects usually decline with time. It is not clear, however, which factors contribute to personal initiative maintenance and which benefits go along with it. In a randomized controlled field experiment with 912 microentrepreneurs in Lomé, Togo, we investigate the influence of need for cognition—a cognitive factor driving proactive behavior—on personal initiative maintenance after training. In addition, we examine the effect of need for cognition on the well‐being consequences of personal initiative maintenance. We show that people high in need for cognition tend to maintain posttraining personal initiative longer than those low in need for cognition. However, contrary to our predictions, need for cognition has no effect on the level of well‐being that results from personal initiative maintenance. Our findings contribute to a better understanding of personal initiative and its maintenance and could be used to increase training effectiveness

The noise-lovers: cultures of speech and sound in second-century Rome

This chapter provides an examination of an ideal of the ‘deliberate speaker’, who aims to reflect time, thought, and study in his speech. In the Roman Empire, words became a vital tool for creating and defending in-groups, and orators and authors in both Latin and Greek alleged, by contrast, that their enemies produced babbling noise rather than articulate speech. In this chapter, the ideal of the deliberate speaker is explored through the works of two very different contemporaries: the African-born Roman orator Fronto and the Syrian Christian apologist Tatian. Despite moving in very different circles, Fronto and Tatian both express their identity and authority through an expertise in words, in strikingly similar ways. The chapter ends with a call for scholars of the Roman Empire to create categories of analysis that move across different cultural and linguistic groups. If we do not, we risk merely replicating the parochialism and insularity of our sources.Accepted manuscrip

Formen und Funktionen von Polemik in den Briefen Augustins: Versuch einer Klassifikation

Due to the conventions of late-antique epistolary politeness, it is not always easy to identify polemical passages in Augustine’s correspondence. The present contribution attempts to discern and classify some recurrent techniques and strategies that are characteristic of letters the addressee of which is him- or herself the target of Augustine’s polemics, i. e. in which polemical rhetoric is blended with diplomacy. After describing some more formal techniques, such as polemical hermeneutics and Refraintechnik, I turn to the rhetorical, i. e. persuasive, functions of polemics in Augustine’s anti-pagan, anti-Donatist and anti-Pelagian letters, using the basic distinction between direct polemics (polemics against the addressee in person) and indirect polemics (polemics against the addressee’s group or friends) as a starting point. Another relevant distinction, taken into account throughout, is whether a polemical letter is primarily designed to impress the immediate addressee or to have an effect on the wider readership that Augustine had to reckon with as soon as a letter was dispatched