Dynamical mean-field approach to materials with strong electronic correlations

We review recent results on the properties of materials with correlated electrons obtained within the LDA+DMFT approach, a combination of a conventional band structure approach based on the local density approximation (LDA) and the dynamical mean-field theory (DMFT). The application to four outstanding problems in this field is discussed: (i) we compute the full valence band structure of the charge-transfer insulator NiO by explicitly including the p-d hybridization, (ii) we explain the origin for the simultaneously occuring metal-insulator transition and collapse of the magnetic moment in MnO and Fe2O3, (iii) we describe a novel GGA+DMFT scheme in terms of plane-wave pseudopotentials which allows us to compute the orbital order and cooperative Jahn-Teller distortion in KCuF3 and LaMnO3, and (iv) we provide a general explanation for the appearance of kinks in the effective dispersion of correlated electrons in systems with a pronounced three-peak spectral function without having to resort to the coupling of electrons to bosonic excitations. These results provide a considerable progress in the fully microscopic investigations of correlated electron materials.Comment: 24 pages, 14 figures, final version, submitted to Eur. Phys. J. for publication in the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator Transitions and Ordering of Microscopic Degrees of Freedom

E-retailing ethics in Egypt and its effect on customer repurchase intention

The theoretical understanding of online shopping behaviour has received much attention. Less focus has been given to the formation of the ethical issues that result from online shopper interactions with e-retailers. The vast majority of earlier research on this area is conceptual in nature and limited in scope by focusing on consumers’ privacy issues. Therefore, the purpose of this paper is to propose a theoretical model explaining what factors contribute to online retailing ethics and its effect on customer repurchase intention. The data were analysed using variance-based structural equation modelling, employing partial least squares regression. Findings indicate that the five factors of the online retailing ethics (security, privacy, non- deception, fulfilment/reliability, and corporate social responsibility) are strongly predictive of online consumers’ repurchase intention. The results offer important implications for e-retailers and are likely to stimulate further research in the area of e-ethics from the consumers’ perspective

Voting with their feet (VWF) endpoint: A meta-analysis of an alternative endpoint in clinical trials, using 5-ASA induction studies in ulcerative colitis

Background: Strict clinical remission endpoints in ulcerative colitis (UC) trials produce low remission rates and do not reflect the good outcomes of UC therapy. We proposed the use of the VWF (Voting With their Feet) endpoint, the percentage of subjects leaving a randomized controlled trial (RCT) arm for lack of efficacy). The aims were 1) to determine if the VWF endpoint can be extracted from 5-aminosalicylate (5-ASA) RCTs in UC; 2) to perform meta-analyses of VWF and clinical remission (CR) endpoints; and 3) to determine the statistical power of the VWF endpoint. Methods: Fixed effects meta-analysis and power calculations were used. Results: In 5 studies, including 1048 subjects, 9.5% of patients left 5-ASA study arms for lack of efficacy, versus 28.3% leaving placebo. The rate of failure to achieve CR was 68.2% with 5-ASA, versus 86.9% with placebo. The relative risk (RR) of treatment failure for 5-ASA using the VWF endpoint was 0.33 (95% confidence interval [CI] 0.24–0.44), which was significantly smaller than with the CR endpoint (RR 0.81, 95% CI 0.76–0.88). The statistical power of VWF was slightly greater than CR. Conclusions: VWF is inexpensive, intuitive, and has similar statistical power to CR. The VWF endpoint can confirm the validity of outcome measures in clinical trials, and estimate real-world clinical efficacy. (Inflamm Bowel Dis 2008)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61878/1/20786_ftp.pd

Consumer perceptions of monetary and non-monetary introductory promotions for new products

Little research has examined how consumers respond to sales promotions in new product categories. This article fills this gap by integrating research on reference prices with literature on sales promotions for new product categories. Existing research suggests that consumers respond more favourably to non-monetary promotions (e.g. extra free promotions) than monetary promotions (e.g. price discounts) because non-monetary promotions are framed as segregated gains rather than reduced losses. However, both kinds of promotions are widely used in practice, suggesting the importance of other contributory factors. With a consumer experiment on a national panel of consumers, this research demonstrates that extra free product promotions are most preferred for existing products, and introductory low-price promotions are preferred for innovative products. The moderating effect of a product's innovativeness is explained via a new relationship in the marketing literature, whereby perceived risk mediates the relationship between perceived innovativeness and a consumer's tendency to stockpile