Local spin polarization in underdoped cuprates with impurities

We present a theory of magnetic (Ni) and nonmagnetic (Zn) impurities substituted into planar Cu sites in the normal state of underdoped cuprates exhibiting a spin gap. Both types of impurities induce magnetic moments on neighboring Cu sites. In the case of Ni these moments partially screen the inherent impurity spin, resulting in an effective S=1/2 moment. The characteristic Kondo scale is found to have a power-law dependence on the coupling constant. We investigate the spatial shape of the impurity-induced spin density, taking into account the presence of short-ranged AF correlations, and calculate the ^{17}O NMR line broadening induced by impurity doping.Comment: To appear in: Physica C, Proceedings of ACS '9

Orbital order out of spin disorder: How to measure the orbital gap

The interplay between spin and orbital degrees of freedom in the Mott-Hubbard insulator is studied by considering an orbitally degenerate superexchange model. We argue that orbital order and the orbital excitation gap in this model are generated through the order-from-disorder mechanism known previously from frustrated spin models. We propose that the orbital gap should show up indirectly in the dynamical spin structure factor; it can therefore be measured using the conventional inelastic neutron scattering method

The Effect on Attitudes of Particular Teaching Methods Used in an Environmental Education Programme

Environmental education programmes should be designed to inspire learners and have enough impact to change learners’ attitudes to environmental issues. These programmes can use a variety of teaching methods – some take the form of lectures, while others allow for group participation. The question arises whether the particular teaching method that is used could have an effect, or can influence, learners’ attitudes. Attitudes are complex and appear to be a consequence of life experiences. Through active involvement, an attempt can be made to intensify those experiences and create a lasting impression that may alter attitudes. This investigation compared the contribution of the lecture method and collaborative learning used in an environmental education programme with the development of positive attitudes on the part of learners who participated in the programme. The findings suggest that, though both methods are effective in changing attitudes, the lecture style did allow for a greater change in attitude over the three-month period. Possible reasons for this unexpected finding are proposed

Order from disorder: Quantum spin gap in magnon spectra of LaTiO_3

A theory of the anisotropic superexchange and low energy spin excitations in a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin Hamiltonian, which invalidate noninteracting spin wave theory. The frustration of classical states is resolved by an order from disorder mechanism, which selects a particular direction of the staggered moment and generates a quantum spin gap. The theory explains well the observed magnon gaps in LaTiO_3. As a test case, a specific prediction is made on the splitting of magnon branches at certain momentum directions.Comment: 5 pages, 2 figures, final versio

Leveraging Virtual Learning Environments for Training Interpreter Trainers

While the demand for conference interpreters in traditional language combinations (the more widely used languages) is decreasing, the need for experts in less widely used languages is rapidly increasing with each enlargement of the EU. Post-war peace-keeping operations as well as warcrime tribunals have also increased the need for high-level interpreters in languages hitherto not used in the international arena and consequently more well-trained interpreter trainers both for traditional programs as well as ad-hoc intensive programs must be available. Interpreters are a highly mobile community of professionals, unable to be physically present in a university for long periods of time to be trained as trainers. The Certificate course for Interpreter Trainers at ETI (University of Geneva) has been offering the only postgraduate course for training interpreter trainers since 1996. To meet the demand for training around the world the Certificate course is now offered in a blended format: Nine months of distance learning are blended with one week of faceto-face learning. The portal (www.unige.ch/eti/certificate/training) offers a rich learning environment with a number of tools to implement the philosophy of collaborative learning. With its public access and a special section for students of interpreting the portal has become an international meeting point for interpreter trainers where participants in the Certificate course interact with interpreting students at ETI, and interpreter trainers from schools around the world can interact with the Certificate teaching staff and students. This paper reports on the first systematic assessment of both the learning environment and the learning outcomes of the Certificate course.La demande d’interprètes de conférence dans les langues les plus répandues est en baisse. Par contre, la demande ne cesse de croître dans des langues moins utilisées, notamment lors de chaque élargissement de l’UE. En parallèle, sur la scène internationale, la demande d’interprètes qualifiés ne cesse d’augmenter que ce soit dans des opérations de maintien de la paix ou dans des tribunaux de crime de guerre. Cette donne contribue à un besoin accru en formateurs d’interprètes tant pour des formations traditionnelles que pour des formations intensives et ponctuelles. Les interprètes forment un corps professionnel très mobile et de ce fait, il est difficile de les mobiliser pour de longues périodes de formation. Le cours du Certificat de formateurs d’interprète dispensé par l’ETI (Université de Genève) est le seul cours postgrade du genre depuis 1996. Pour répondre à la demande venue du monde entier, le cours est maintenant offert dans un format hybride, alliant neuf mois de distance à une semaine présentielle à Genève. Le portail utilisé (www.unige.ch/eti/certificate/training) offre un environnement d’apprentissage collaboratif élaboré. De part son interface accessible à tout public et une section réservée aux étudiants en interprétation, il devient un espace de rencontre entre différentes communautés. Cet article présente les premiers résultats obtenus, au niveau de l’environnement d’apprentissage et au niveau de l’apprentissage lui-même

Theory of anomalous magnon softening in ferromagnetic manganites

In metallic manganites with low Curie temperatures, a peculiar softening of the magnon spectrum close to the magnetic zone boundary has experimentally been observed. Here we present a theory of the renormalization of the magnetic excitation spectrum in colossal magnetoresistance compounds. The theory is based on the modulation of magnetic exchange bonds by the orbital degree of freedom of double-degenerate e_g electrons. The model considered is an orbitally degenerate double-exchange system coupled to Jahn-Teller active phonons which we treat in the limit of strong onsite repulsions. Charge and coupled orbital-lattice fluctuations are identified as the main origin of the unusual softening of the magnetic spectrum