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Acke B.,Catholic University of Leuven | Acke B.,Fund for Scientific Research
EAS Publications Series | Year: 2011

I give an overview of the recent scientific results based on observations of PAH emission from circumstellar disks around young stars. The stellar radiation field plays a key role in the excitation and destruction of the PAH molecules in the disk. The detection rate of PAH emission in disks is optimal for stars of spectral type A. Around stars of similar temperature, the disk structure determines the PAH emission strength: disks with a flared geometry produce stronger PAH emission than flattened disks. The spectral properties of the emission features, indicative of the chemistry of the emitting hydrocarbons, is closely linked to the central star radiation field. The main PAH features shift to redder wavelengths with decreasing stellar effective temperature. This trend has been interpreted as an indication for a higher aliphatic/aromatic ratio of the hydrocarbon mixture around cool stars with respect to hot stars. An alternative explanation may be a more significant contribution to the infrared emission of very small grains around cooler stars. © EAS, EDP Sciences 2011. Source


Blaauw M.,Technical University of Delft | De Corte F.,Ghent University | De Corte F.,Fund for Scientific Research
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

In 2003, an overview paper was published with recommended nuclear data for use in the k0-standardization of instrumental neutron activation analysis. At the same time, these data were made available by the International Union of Pure and Applied Chemistry in the form of a downloadable database. In the process of verifying the consistency of the nuclear data inside the k 0-IAEA software with these published fundamental databases of recommended k0-data, a variety of inconsistencies within and between the two datasets came to light. In this paper, we present the inconsistencies and resolve them where possible. Experimental verification of k0 values for selected uranium fission products, as performed in Delft, is also presented. © 2010 Elsevier B.V. All rights reserved. Source


Boulanger N.,University of Mons | Boulanger N.,Fund for Scientific Research | Cook P.P.,Kings College London | Ponomarev D.,University of Mons
Journal of High Energy Physics | Year: 2012

In a spacetime of dimension n, the dual graviton is characterised by a Young diagram with two columns, the first of length n - 3 and the second of length one. In this paper we perform the off-shell dualisation relating the dual graviton to the double-dual graviton, displaying the precise off-shell field content and gauge invariances. We then show that one can further perform infinitely many off-shell dualities, reformulating linearised gravity in an infinite number of equivalent actions. The actions require supplementary mixed-symmetry fields which are contained within the generalised Kac-Moody algebra E 11 and are associated with null and imaginary roots. © SISSA 2012. Source


Guns M.,Catholic University of Louvain | Guns M.,Fund for Scientific Research | Vanacker V.,Catholic University of Louvain
Environmental Earth Sciences | Year: 2013

Tropical mountain regions are prone to landslide hazards. Given the current land pressure with increasing occupation of steep uplands, landslide hazards are expected to increase in the near future. Understanding the factors that control landslide hazards is therefore essential. Rare event logistic regression allows us to perform a robust detection of landslide controlling factors. This technique is here applied to the tropical Andes to evaluate the impact of dynamic land cover changes on landslide occurrences. Land cover change trajectories (i.e. dynamic evolution of land cover through time) were specifically included in the probabilistic landslide analysis. While natural physical processes such as slope undercutting by rivers and failure of oversteepened slopes are important in this tropical mountainous site, landslides are increasingly associated with human activities. The data show that land cover trajectories are associated with landslide patterns. In this humid mountainous site, forest degradation does not lead to a measurable increase in landslide occurrence. However, few years after forests are converted to pastures, a rapid decline of slope stability is observed. Land cover conversion from forest to pasture permanently reduces slope stability. It is assumed that major changes in soil properties and hydrology induced by the vegetation conversion play a role in accelerating landslide hazards. © 2013 Springer-Verlag Berlin Heidelberg. Source


Bastin C.,University of Liege | Bastin C.,Fund for Scientific Research | Salmon E.,University of Liege
European Journal of Clinical Nutrition | Year: 2014

Lifestyle modification offers a promising way of preventing or delaying Alzheimer's disease (AD). In particular, nutritional interventions can contribute to decrease the risk of dementia. The efficacy of such interventions should be assessed in individuals thought to be prone to AD. It is therefore necessary to identify markers that may help detecting AD as early as possible. This review will focus on subtle neuropsychological changes that may already exist in the predementia phase, and that could point to individuals at risk of dementia. Episodic memory decline appears consistently as the earliest sign of incipient typical AD. An episodic memory test that ensures deep encoding of information and assesses retrieval with free as well as cued recall appears as a useful tool to detect patients at an early stage of AD. Beyond the memory domain, category verbal fluency has been shown to decline early and to predict progression to AD. Moreover, in line with current diagnosis criteria for prodromal AD, combining neuropsychological scores and neuroimaging data allows a better discrimination of future AD patients than neuroimaging or neuropsychological data alone. Altogether, the detection of cognitive changes that are predictive of the typical form of probable AD already in the predementia stage points to at risk people who are the best target for therapeutic interventions, such as nutrition or physical exercise counseling or dietary interventions. © 2014 Macmillan Publishers Limited. Source

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