Excitonic effects in the optical properties of CdSe nanowires

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires.Our results demonstrate how some approximations commonly used in bulk systems fail at this nano-scale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model that describes the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.Comment: submitte

Construction of the B88 exchange-energy functional in two dimensions

We construct a generalized-gradient approximation for the exchange-energy density of finite two-dimensional systems. Guided by non-empirical principles, we include the proper small-gradient limit and the proper tail for the exchange-hole potential. The observed performance is superior to that of the two-dimensional local-density approximation, which underlines the usefulness of the approach in practical applications

Combining models in discrete discriminant analysis

When conducting discrete discriminant analysis, alternative models provide different levels of predictive accuracy which has encouraged the research in combined models. This research seems to be specially promising when small or moderate sized samples are considered, which often occurs in practice. In this work we evaluate the performance of a linear combination of two discrete discriminant analysis models: the first-order independence model and the dependence trees model. The proposed methodology also uses a hierarchical coupling model when addressing multi-class classification problems, decomposing the multi-class problems into several bi-class problems, using a binary tree structure. The analysis is based both on simulated and real datasets. Results of the proposed approach are compared with those obtained by random forests, being generally more accurate. Measures of precision regarding a training set, a test set and cross-validation are presented. The R software is used for the algorithms' implementation.info:eu-repo/semantics/submittedVersio

Selection of variables in Discrete Discriminant Analysis

In Discrete Discriminant Analysis one often has to deal with dimensionality problems. In fact, even a moderate number of explanatory variables leads to an enormous number of possible states (outcomes) when compared to the number of objects under study, as occurs particularly in the social sciences, humanities and health-related elds. As a consequence, classi cation or discriminant models may exhibit poor performance due to the large number of parameters to be estimated. In the present paper, we discuss variable selection techniques which aim to address the issue of dimensionality. We speci cally perform classi cation using a combined model approach. In this setting, variable selection is particularly pertinent, enabling the handling of degrees of freedom and reducing computational cost

Do loyalty cards enhance loyalty in the pharmaceutical sector?

This paper aims to analyze the influence of the “Portuguese Pharmacies card” (PP card) on the pharmacies’ customers behaviour. It also intends to examine whether marketing stimuli influence consumers’ buying behavior with regard to non-prescription medicines / health and wellness product / pharmaceutical services (NP/HW/PS) and to understand if the consumer social-demographic characteristics influence purchase decisions and customers’ loyalty. The investigation is based on the results obtained through an online survey. Exploratory descriptive analysis, based on a sample of 385 customers, is used to empirically verify the hypothesis under study. The Marketing of stimuli considered in this research include four communication tools: advertising, sales promotions, word of mouth and the sales force. According to the results obtained, the degree of influence attributed to these various communication tools in the buying decision does not differ significantly in terms of socio-demographic categories. On the other hand, the purchase volume of NP/HW/PS is significantly dependent on the influence of advertising and sales promotions in the purchase decision. Furthermore, impulse buying of NP/HW/PS is significantly dependent on the influence of advertising, promotions and WOM. We conclude that the Portuguese Pharmacies card indeed contributes to customer loyalty in the establishments where it is present. In order to meet customer expectations, a loyalty program should be adjusted over time, seeking to stimulate the satisfaction and reliance in this program.info:eu-repo/semantics/acceptedVersio

R-symmetric Gauge Mediation and the MRSSM

This is an invited summary of a seminar talk given at various institutions in the United States and Canada. After a brief introduction, a review of the minimal R-symmetric supersymmetric standard model is given, and the benefits to the flavor sector are discussed. R-symmetric gauge mediation is an attempt to realize this model using metastable supersymmetry breaking techniques. Sample low energy spectra are presented and tuning is discussed. Various other phenomenological results are summarized.Comment: 14 pages, invited Brief Review, submitted to Modern Physics Letters A; v2: replaced Figure 1, updated acknowledgments, fixed typo

Women working in Refrigeration, Air-Conditioning and Heat Pumps: a Worldwide Survey

The International Institute of Refrigeration (IIR) and the United Nations Environment Programme (UNEP) OzonAction undertook a worldwide survey on women in cooling. The aim was to better understand the background, motivation, challenges, and opportunities faced by women working in the in Refrigeration, Air-Conditioning and Heat Pumps (RACHP) sector. In total 810 women replied to the survey. The results indicated a high industry retention rate, with 47% of the women working in the RACHP sector for more than 10 years. The three main challenges identified were: difficulties in managing a healthy work-life balance, lack of career advancement opportunities and stereotypes or prejudice about women from clients or customers. Conversely, the most proud career achievements were earning the respect and confidence of colleagues, developing a new product/service and training/teaching people. The survey identified the challenges and opportunities faced by women working in the RACHP sector providing valuable insight to the development of new policies and initiatives to support women