Probabilistic change detection and visualization methods for the assessment of temporal stability in biomedical data quality

The final publication is available at Springer via http://dx.doi.org/DOI 10.1007/s10618-014-0378-6. Published online.Knowledge discovery on biomedical data can be based on on-line, data-stream analyses, or using retrospective, timestamped, off-line datasets. In both cases, changes in the processes that generate data or in their quality features through time may hinder either the knowledge discovery process or the generalization of past knowledge. These problems can be seen as a lack of data temporal stability. This work establishes the temporal stability as a data quality dimension and proposes new methods for its assessment based on a probabilistic framework. Concretely, methods are proposed for (1) monitoring changes, and (2) characterizing changes, trends and detecting temporal subgroups. First, a probabilistic change detection algorithm is proposed based on the Statistical Process Control of the posterior Beta distribution of the Jensen–Shannon distance, with a memoryless forgetting mechanism. This algorithm (PDF-SPC) classifies the degree of current change in three states: In-Control, Warning, and Out-of-Control. Second, a novel method is proposed to visualize and characterize the temporal changes of data based on the projection of a non-parametric information-geometric statistical manifold of time windows. This projection facilitates the exploration of temporal trends using the proposed IGT-plot and, by means of unsupervised learning methods, discovering conceptually-related temporal subgroups. Methods are evaluated using real and simulated data based on the National Hospital Discharge Survey (NHDS) dataset.The work by C Saez has been supported by an Erasmus Lifelong Learning Programme 2013 Grant. This work has been supported by own IBIME funds. 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Computational studies of the thermal fragmentation of P-arylphosphiranes: Have arylphosphinidenes been generated by this method?

CASSCF, CASPT2, CCSD(T), and (U)B3LYP electronic structure calculations have been performed in order to investigate the thermal fragmentation of P-phenylphosphirane (1) to phenylphosphinidene (PhP) and ethylene. The calculations show that generation of triplet PhP via a stepwise pathway is 21 kcal mol-1 less endothermic and has a 12 kcal mol-1 lower barrier height than concerted fragmentation of 1 to give singlet PhP. The formation of singlet PhP via a concerted pathway is predicted to be stereospecific, whereas formation of triplet PhP is predicted to occur with complete loss of stereochemistry. However, calculations on fragmentation of anti-cis-2,3-dimethyl-P-mesitylphosphirane (cis-1Me) to triplet mesitylphosphinidene (MesP) indicate that this reaction should be more stereospecific, in agreement with the experimental results of Li and Caspar. Nevertheless, with a predicted free energy of activation of 42 kcal mol -1, the formation of MesP from cis-1Me is not likely to have occurred in an uncatalyzed reaction at the temperatures at which this phosphirane has been pyrolyzed. © 2005 American Chemical Society.link_to_subscribed_fulltex

Stoichiometric oxidations of σ-bonds: Radical and possible non-radical pathways

Many transition metal complexes accomplish or catalyze the oxidation of C{single bond}H, O{single bond}H, and other σ-bonds. Under aerobic conditions, metal complexes typically modulate an autoxidation radical chain. In anaerobic reactions, a metal complex can be the reactive species that attacks the σ-bond, in many cases by abstracting a hydrogen atom from the substrate. Examples described here include the oxidation of alkylaromatic compounds by ruthenium oxo complexes and reactions of deprotonated iron(III) complexes. In general, these reactions occur with addition of H+ to a ligand and e- to the metal center. Rate constants for such hydrogen-atom transfer reactions can, in many cases, be predicted by the Marcus cross relation. Autoxidation and metal-mediated radical mechanisms are so prevalent that proposals of non-radical oxidations of C{single bond}H bonds carry a higher burden of proof. It is argued here that the oxidation of H2 by OsO4 occurs by a non-radical, [3 + 2] mechanism. OsO4 oxidizes alkanes under similar aqueous conditions. For example, isobutane is oxidized to tert-butanol, and cyclohexane to adipate and succinate. The alkane oxidations do not have the hallmarks of a radical mechanism but sufficient questions remain that a radical pathway cannot be excluded at this time. © 2006 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

LPV Control Approaches in View of Comfort Improvement of Automotive Suspensions Equipped with MR Dampers

International audienceMany studies have shown the importance of automotive suspension systems in vehicle dynamics, see for instance [10], [26], [33] and references therein. Except for passive suspensions whose characteristics are invariant, the semi-active and active suspensions can change their properties by using controlled external signals (voltage, current...). This is why the latter suspensions have been studied intensively in recent years. However, up to now, only the semi-active suspensions are used widely in automotive industry. Indeed, comparedwith fully active suspensions, semi-active ones can achieve the main performance objectives (see [17], [27]) while they are smaller in weight and volume, cheaper in price, more robust and less energy consuming (see also [9], [10], [16], [19]). So far, the control problem for semi-active suspensions has been tackled with many approaches during the last three decades. One of the first comfort-oriented control methods, successfully applied in commercial vehicles, is the Skyhook control proposed by Karnopp et al. [18]. Then, optimal control [12], [34], clipped optimal control [24], [36], [11], H∞ control [30], [31] or Model Predictive Control [4], [28] have been considered. Recently, two new control design methods for semiactive suspensions using the LPV techniques have been presented. The first one, proposed in [29], can be applied for all kinds of semi-active dampers where only the bounds on damping coefficients and on the damper forces are necessary for the controller design. In the other one, proposed in [7], the nonlinearities of the semi-active damper (the bi-viscosity and the hysteresis) are taken into consideration. The comparison of these two recent LPV-based techniques on a nonlinear Magneto-Rheological (MR) damper model is proposed this chapter. The chapter is organized as follows: In section I, a brief bibliography concerning the modelling of semi-active dampers is given and two specific control-oriented models are detailed and will be used for the synthesis of the LPV controllers. In section II, the control problem of automotive suspension control is formulated in a common way so that the methods proposed in [29] (section III) and [7] (section IV) can be applied. Section V is devoted to numerical simulations on a nonlinear quarter car model. Some remarks and conclusions end this chapter