OLAP for health statistics: how to turn a simple spreadsheet into a powerful analytical tool

Over the last ten years, Online Analytical Processing (OLAP) has become a very popular tool for interactive analysis of multidimensional information. Providing online operation and flexible summarising, tabulating and charting options, it has become an essential part of the decision support process in corporate setting. Our aim is to demonstrate how easily applicable and useful OLAP can be in the public sector. To achieve that, we used data compiled from different sources for the purpose of exploring the relations between causes of death (according to ICD-10) and socio-economic characteristics (educational level, marital status, profession, etc.) for selected years 1992, 1995 and 1998 in Slovenia. Using a standard personal computer and the Windows® platform, the application was implemented in Microsoft® Excel 2000, without any programming. After data cleansing (elimination of incorrect entries, duplicates and inconsistencies based on exploratory statistical methods), the case-based spreadsheet data was instantly converted into an OLAP application with the user-friendly pivot table technology. A bonus of this approach is that the results can be made directly accessible over the WWW by publishing the workbook to a web server. Provided that the user has Microsoft® Internet Explorer and Microsoft® Office 2000 installed, all the drill-in, drill-out and dimension-swapping capabilities are accessible within the browser, while the data source remains fully protected. Privacy constraints are respected since all the information is only provided at the aggregate level. Even though our dataset provides exhaustive coverage of mortality at the national level, storage and processing capabilities did not prove to be an issue. Hence, we argue that OLAP methodology should find a place in health statistics. With proper data collection and/or transformations, informative comparisons within the study population and with international databases become readily accessible. The key advantage of OLAP over relational database management systems and ordinary tables is interactive browsing of multidimensional and hierarchical data, while OLAP can also aid data integrity checking and reporting

Nonequilibrium propagation and decay of a bound pair in driven t-J models

We perform an accurate time-dependent numerical study of out-of-equilibrium response of a bound state within t-J systems on a two-leg ladder and a square lattice. We show that the bound hole pair decays with the onset of finite steady current if both mechanisms for binding and the dissipation share matching degrees of freedom. Moreover, by investigating the mechanism of decay on the square lattice we find that the dynamics is governed by the decay in the direction perpendicular to the electric field, leading to much shorter decay times in comparison to the ladder where such dynamics is topologically restricted

Optical conductivity in the t-J-Holstein Model

Using recently developed numerical method we compute charge stiffness and optical conductivity of the t-J model coupled to optical phonons. Coherent hole motion is most strongly influenced by the electron-phonon coupling within the physically relevant regime of the exchange interaction. We find unusual non-monotonous dependence of the charge stiffness as a function of the exchange coupling near the crossover to the strong electron-phonon coupling regime. Optical conductivity in this regime shows a two-peak structure. The low-frequency peak represents local magnetic excitation, attached to the hole, while the higher-frequency peak corresponds to the mid infrared band that originates from coupling to spin-wave excitations, broadened and renormalized by phonon excitations. We observe no separate peak at or slightly above the phonon frequency. This finding suggests that the two peak structure seen in recent optical measurements is due to magnetic excitations coupled to lattice degrees of freedom via doped charge carriers.Comment: 6 pages, 5 figures, submitted to PR