Band structures of Cu2nSnS4 and Cu2nSnSe4 from many-body methods

We calculate the band structures of kesterite and stannite Cu2ZnSnS4 and Cu2ZnSnSe4, using a state-of-the-art self-consistent GW approach. Our accurate quasiparticle states allow to discuss: the dependence of the gap on the anion displacement; the key-role of the non-locality of the exchange-correlation potential to obtain good structural parameters; the reliability of less expensive hybrid functional and GGA+U approaches. In particular, we show that even if the band gap is correctly reproduced by hybrid functionals, the band-edge corrections are in disagreement with self-consistent GW results, which has decisive implications for the positioning of the defect levels in the band gap.Comment: accepted for publication in App. Phys. Lett. (2011

Intercultural communicative competence is essential for students of international business - but can it be taught? The case of third-year BCom students

Intercultural communicative competence is essential for graduates wishing to work in the business sector. Such competence has become desirable for graduates who see themselves working in “demanding and highly-challenging international environments” (Sain, Kužnin and Roje 2017, 55‒56). In spite of the need for well-developed intercultural competence in the workplace, students of Economic and Business Science are rarely deliberately equipped with an understanding of what language, culture and communication entail. Against this background, we investigated if an intervention, in the form of a 28-lecture undergraduate course, can develop third-year BCom students’ intercultural competence so as to prepare them to deal with the heterogeneity that they will encounter in the workplace (and elsewhere), both in multilingual and multi-cultural South Africa and abroad.Based on eight of the skills and attributes identified by Deardorff (2004) as being markers of interculturally competent individuals (such as knowledge of self and others, respect, critical thinking skills, and an awareness of the importance of being interculturally competent), students (n=18) were assessed prior to the commencement of the course and again upon completion thereof. Pre- and post-course questionnaires were analysed qualitatively and quantitatively, and data were coded according to the eight Deardorff (2004) markers of intercultural competence. Additionally, a focus group discussion (n = 5) was held at the end of the course. The data showed that development took place in the students’ attitudes, knowledge and skills related to intercultural communicative competence. Certain markers of intercultural communicative competence, however, showed more substantial development than others, the notable marker showing such development being critical thinking skills.The finding is that skills indicative of intercultural competence can indeed be developed by means of a curriculum in such a way that students think more critically about (i) cultural and linguistic diversity and (ii) their responsibility as future leaders to communicate optimally in diverse cultural settings. Deliberately including courses on intercultural communication in programmes for students (not only students in Humanities and Social Sciences) could contribute to personal and professional development of students and lead to graduates who are better prepared for a career in multicultural national and international business sectors. Likewise, the introduction of in-service training in intercultural communicative competence can be considered for those who are no longer students, thereby contributing to improved intercultural communication in the workplace

Monitoring and lifetime prediction of pvc cables: methodology by multiscale and multidisciplinary approach

Monitoring of the PVC cables as well as the prediction of their residual lifetime are important issues for the maintenance of the French nuclear power plants (NPPs). To date, the unanimously end of life criterion admitted for these cables is a 50% value of elongation at break and, to our knowledge, only destructive tests give access to this parameter. This study reports a relationship between elongation at break of the PVC and their plasticizer content. This correlation opens the door to a monitoring directly on site or by micro sampling since all classic laboratory techniques able to measure this content become ways to judge the condition of the PVC sheaths and insulators. In addition, this study demonstrates the feasibility of prediction of industrial PVC behavior changes. This model, adapted to the case of thin films, involved tools of chemical kinetics and the implementation of a constitutive model

High-vacuum-compatible high-power Faraday isolators for gravitational-wave interferometers

Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorption–degraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers

DC-readout of a signal-recycled gravitational wave detector

All first-generation large-scale gravitational wave detectors are operated at the dark fringe and use a heterodyne readout employing radio frequency (RF) modulation-demodulation techniques. However, the experience in the currently running interferometers reveals several problems connected with a heterodyne readout, of which phase noise of the RF modulation is the most serious one. A homodyne detection scheme (DC-readout), using the highly stabilized and filtered carrier light as local oscillator for the readout, is considered to be a favourable alternative. Recently a DC-readout scheme was implemented on the GEO 600 detector. We describe the results of first measurements and give a comparison of the performance achieved with homodyne and heterodyne readout. The implications of the combined use of DC-readout and signal-recycling are considered.Comment: 11 page

A Cross-correlation method to search for gravitational wave bursts with AURIGA and Virgo

We present a method to search for transient GWs using a network of detectors with different spectral and directional sensitivities: the interferometer Virgo and the bar detector AURIGA. The data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross-correlation. To limit the computational load, this coherent analysis step is performed around time-frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds. The final selection of GW candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator. The method has been tested on one day of data of AURIGA and Virgo during September 2005. The outcomes are compared to the results of a stand-alone time-frequency coincidence search. We discuss the advantages and the limits of this approach, in view of a possible future joint search between AURIGA and one interferometric detector.Comment: 11 pages, 6 figures, submitted to CQG special issue for Amaldi 7 Proceeding

The variable finesse locking technique

Virgo is a power recycled Michelson interferometer, with 3 km long Fabry-Perot cavities in the arms. The locking of the interferometer has been obtained with an original lock acquisition technique. The main idea is to lock the instrument away from its working point. Lock is obtained by misaligning the power recycling mirror and detuning the Michelson from the dark fringe. In this way, a good fraction of light escapes through the antisymmetric port and the power build-up inside the recycling cavity is extremely low. The benefit is that all the degrees of freedom are controlled when they are almost decoupled, and the linewidth of the recycling cavity is large. The interferometer is then adiabatically brought on to the dark fringe. This technique is referred to as variable finesse, since the recycling cavity is considered as a variable finesse Fabry-Perot. This technique has been widely tested and allows us to reach the dark fringe in few minutes, in an essentially deterministic way