A general multivariate latent growth model with applications in student careers Data warehouses

The evaluation of the formative process in the University system has been assuming an ever increasing importance in the European countries. Within this context the analysis of student performance and capabilities plays a fundamental role. In this work we propose a multivariate latent growth model for studying the performances of a cohort of students of the University of Bologna. The model proposed is innovative since it is composed by: (1) multivariate growth models that allow to capture the different dynamics of student performance indicators over time and (2) a factor model that allows to measure the general latent student capability. The flexibility of the model proposed allows its applications in several fields such as socio-economic settings in which personal behaviours are studied by using panel data.Comment: 20 page

Ferroelectricity in multiferroic magnetite Fe3O4 driven by noncentrosymmetric Fe2+/Fe3+ charge-ordering: First-principles study

By means of first-principles simulations, we unambiguously show that improper ferroelectricity in magnetite in the low-temperature insulating phase is driven by charge-ordering. An accurate comparison between monoclinic ferroelectric Cc and paraelectric P2/c structures shows that the polarization arises because of "shifts" of electronic charge between octahedral Fe sites, leading to a non-centrosymmetric Fe2+/Fe3+ charge-ordered pattern. Our predicted values for polarization, in good agreement with available experimental values, are discussed in terms of point-charge dipoles located on selected Fe tetrahedra, pointing to a manifest example of electronic ferroelectricity driven by charge rearrangement.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev.

Influence of extraction methods on the composition of essential oils of Achillea millefolium L. from Lithuania

In this study, flowering aerial parts of Achillea millefolium were used as a matrix for supercritical CO2 extraction (SFE) of volatile oil. The collected extracts were analyzed by GC-FID and GC-MS methods and their composition were compared with that of the essential oil isolated by hydrodistillation (HD). The composition of the essential oil obtained by hydrodistillation and SFE methods is widely different. Indeed, the SFE volatile oil had a pale yellow color whereas the HD oil had a blue color due to the presence of chamazulene (48.0% vs. 4.3%). Other important constituents of HD oil were (E)- caryophyllene (19.5 %) and γ-muurolene (13.1%). The CO2 supercritical extract was dominated by (E)-caryophyllene (26.0%), γ-muurolene (22.0%), and caryophyllene oxide (8.1%)

Strain-gradient-induced switching of nanoscale domains in free-standing ultrathin films

We report first-principle atomistic simulations on the effect of local strain gradients on the nanoscale domain morphology of free-standing PbTiO$_3$ ultrathin films. First, the ferroelectric properties of free films at the atomic level are reviewed. For the explored thicknesses (10 to 23 unit cells), we find flux-closure domain structures whose morphology is thickness dependent. A critical value of 20 unit cells is observed: thinner films show structures with 90$^\circ$ domain loops, whereas thicker ones develop, in addition, 180$^\circ$ domain walls, giving rise to structures of the Landau-Lifshitz type. When a local and compressive strain gradient at the top surface is imposed, the gradient is able to switch the polarization of the downward domains, but not to the opposite ones. The evolution of the domain pattern as a function of the strain gradient strength consequently depends on the film thickness. Our simulations indicate that in thinner films, first the 90$^\circ$ domain loops migrate towards the strain-gradient region, and then the polarization in that zone is gradually switched. In thicker films, instead, the switching in the strain-gradient region is progressive, not involving domain-wall motion, which is attributed to less mobile 180$^\circ$ domain walls. The ferroelectric switching is understood based on the knowledge of the local atomic properties, and the results confirm that mechanical flexoelectricity provides a means to control the nanodomain pattern in ferroelectric systems.Comment: 9 pages, 6 figure

A Comparison of Quality of Life Measures in Husbands of Women with Breast Cancer

The Quality of Well-Being Scale (QWB-SA) and Medical Outcome Study SF-36 short form (SF-36) are popular health-related quality of life (HRQOL) assessment tools; however, it is unclear whether these measures overlap enough to be interchangeable, and if not, which might be a better choice. This study examined conceptual overlap, validity, and relation with psychosocial functioning of the QWB-SA and SF-36 in a sample of partners of women undergoing adjuvant treatment for breast cancer. Partners (n = 79) of breast cancer patients, recruited in a chemotherapy infusion clinic, completed the QWB-SA and SF-36 and additional psychosocial measures. Descriptive content review shows that both instruments provide a breadth of HRQOL coverage including physical health, mental health, social functioning, role functioning and general health perceptions; however, more QWB-SA scales suffered floor effects. Subscales correlated, with the strongest correlations between the QWB-SA total score and the mental health scales of the SF-36. The QWB-SA and the SF-36 Mental Health Component Summary score, but not the SF-36 Physical Component Summary score were strongly correlated to measures of mood, satisfaction with life, burden, and social support. The QWB-SA and SF-36 measure distinct aspects of HRQOL. Each instrument presents distinct advantages and disadvantages in coverage of particular domains. Labels assigned to SF-36 scales more accurately reflect what they measure. The SF-36 appeared more sensitive to the impact that psychological health played on overall assessment of HRQOL in these partners

STRATEGIC OPTION OF MOBILE PHONE OPERATOR ORANGE UNDER CRISIS CONDITIONS

The current financial and economic crisis has affected many sectors, but companies have tried to implement marketing strategies adapted to the context. Telecommunication field was affected to a lesser extent, given the customers’ need for communication, need that doesn’t go away, but that can be achieved through orientation to other service providers. As a research methodology, we used qualitative methods and empirical data on the evolution of Orange mobile operator under crisis conditions, and compared with other operators. The main advantage of these methods is the adaptation to existing resources and external identifying limitations. The objective of this study is to understand how to manage effectively a crisis by applying different marketing strategies adapted to the changing customer needs.telecommunications; strategy; crisis; opportunity;option