The xraylib library for X-ray–matter interactions. Recent developments

This work presents the recent developments of xraylib, an ANSI C library that provides convenient access to a large number of X-ray related databases, with a focus on quantitative X-ray fluorescence applications. The enhancements include improved X-ray fluorescence production cross sections that take into account cascade effects and M-lines, as well as revised line energies, atomic level widths, Compton broadening profiles etc. A full overview of the complete application programming interface is presented.     

A new concept in lightning parameters measurement

Nowadays the electrical activity measured in tall objects has been widely characterized, but the collected data of lightning rods installed in buildings do not amount to enough to obtain reliable statistics. The measures stored at relatively few points are not representative of the different types of installations. Furthermore, the protection model applied for lightning air terminal installations is based on theoretical models. This paper describes the design of a micro-station to measure some lightning parameters in real lightning air terminal installations correlated to the nature of emplacement instead of triggering lightning or choosing points with a high number of lightning impacts.     

Enzymatic resolution of trans-4-(4'-fluorophenyl)-3-hydroxymethylpiperidines, key intermediates in the synthesis of (-)-Paroxetine.

Two Candida antarctica lipases catalyze the enantioselective acylation of N-substituted trans-4-(4'-fluorophenyl)-3-hydroxymethylpiperidines in organic solvents. These two lipases show opposite stereochemical preference in these processes. Both enantiomers can be obtained in their optically pure forms. The (3S,4R) isomer, is an intermediate for the synthesis of (-)-Paroxetine.     

Pre-emption in resource-constrained project scheduling

The Resource-Constrained Project Scheduling Project (RCPSP), together with some of its extensions, has been widely studied. A fundamental assumption in this basic problem is that activities in progress are non-preemptable. Very little effort has been made to uncover the potential benefits of discrete activity pre-emption, and the papers dealing with this issue have reached the conclusion that it has little effect on project length when constant resource availability levels are defined. In this paper we show how three basic elements of many heuristics for the RCPSP – codification, serial SGS and double justification – can be adapted to deal with interruption. The paper is mainly focussed on problem 1_PRCPSP, a generalization of the RCPSP where a maximum of one interruption per activity is allowed. However, it is also shown how these three elements can be further adapted to deal with more general pre-emptive problems. Computational experiments on the standard j30 and j120 sets support the conclusion that pre-emption does help to decrease project length when compared to the no-interruption case. They also prove the usefulness of the justification in the presence of pre-emption. The justification is a RCPS technique that can be easily incorporated into a wide range of algorithms for the RCPSP, increasing their solution quality – maintaining the number of schedules calculated.     

Recovering risk-neutral probability density functions from options prices using cubic splines and ensuring nonnegativity

We present a new approach to estimate the risk-neutral probability density function (pdf) of the future prices of an underlying asset from the prices of options written on the asset. The estimation is carried out in the space of cubic spline functions, yielding appropriate smoothness. The resulting optimization problem, used to invert the data and determine the corresponding density function, is a convex quadratic or semidefinite programming problem, depending on the formulation. Both of these problems can be efficiently solved by numerical optimization software.     

Skilled workforce scheduling in Service Centres

The Skilled Workforce Project Scheduling Problem (SWPSP) is a complex problem of task scheduling and resource assignment that comes up in the daily management of many company Service Centres (SC). The SWPSP considers many real characteristics faced daily by the SC: client-company service quality agreements that establish maximum dates for the beginning and the end of tasks with penalties for delays, criticality levels indicating the client-priority in processing each task, generalized precedence relationships that can produce cycle structures, time period and percentage time lags and variable task durations depending on the worker executing the task. Furthermore, the SC workforce is made up of specialist workers characterised by efficiency levels showing their efficiency and speed executing the several types of tasks. Each worker has his or her own timetable.     

Novel KF-TiO2catalysts for oxidative dehydrogenation of isobutane

A novel type of catalysts, KF-TiO₂, efficient for the oxidative dehydrogenation (ODH) of isobutane is presented. The effect of KF content and calcination temperature was studied. In the reaction conditions explored, the best performance (73 % selectivity to isobutene at 10.5 % conversion of isobutane) was observed over a catalyst with KF/TiO₂ = 0.2 (mol/mol). The surface properties of the catalysts were investigated by SPS (Surface Photo-voltage Spectroscopy) and XPS. The promotion effect of KF in the catalysts can be attributed to the formation of an oxyfluoro-compound, K₂Ti₄O₈F₂.     

Encryption test of pseudo-aleatory messages embedded on chaotic laser signals: An information theory approach

In this Letter, we make use of two information-theory based indicators to measure the goodness of two encryption schemes commonly used within the context of chaotic communications. In particular, we have shown that the computation of the normalized Shannon entropy and the MPR-Statistical Complexity measure [M.T. Martín, A. Plastino, O.A. Rosso, Phys. Lett. A 311 (2003) 126, P.W. Lamberti, M.T. Martín, A. Plastino, O.A. Rosso, Physica A 334 (2004) 119] for different chaotic laser signals can lead to statistically significant criteria to assess the quality of several encryption techniques. The proposed measures allow, in some cases, to detect the presence of a message embedded within a chaotic carrier. They also reveal that the Chaos Modulation scheme is more reliable from the statistical point of view, when compared with the Chaos Shift Keying.     

Synthesis of halogenated hydrazone derivatives and their applicability in the preparation of 4-chloropyrazoles

Reaction of hydrazonic derivatives 1 with N-chlorosuccinimide affords monohalogenated hydrazones 3 with nearly quantitative yields. When 3 is treated with mineral acids or trifluoroacetic acid 4-chloropyrazoles are isolated.