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See detailA new methodological approach for error distributions selection in Finance
Hambuckers, julien ULg; Heuchenne, Cédric ULg

E-print/Working paper (2014)

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the ... [more ▼]

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we don't use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure (Mercurio and Spokoiny, 2004): the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures (Berk-Jones tests, kernel density-based selection, censored likelihood score, coverage probability) based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behavior in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]

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See detailInitiation à la papyrologie documentaire. Note du cours de Jean A. Straus
Straus, Jean ULg

Learning material (2014)

Manuel de papyrologie documentaire

Detailed reference viewed: 98 (6 ULg)
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See detailProtecting Assets Under Non-Parametric Market Conditions
Choffray, Jean-Marie ULg; Pahud de Mortanges, Charles ULg

E-print/Working paper (2014)

Under non-parametric market conditions, investors usually become more concerned about the return of their money than about the return on their money. Protecting assets becomes the surest if not the only ... [more ▼]

Under non-parametric market conditions, investors usually become more concerned about the return of their money than about the return on their money. Protecting assets becomes the surest if not the only path to survival and growth. High frequency trading systems, over leveraged shadow entities, flash crashes, and stealth central bank actions, to name a few, contribute to create a “Rumsfeldian” type of world in which decision makers have to cope not only with “Known knowns” – things they know that they know – but also with “Unknown unknowns” – things they don’t know that they don’t know! The goal of this paper is to explore such a conceptual model of the “Unknown” and to derive from it a concise and coherent set of battle-tested heuristics aimed at designing effective investment strategies to protect assets. [less ▲]

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See detailCapillary-driven bi-dimensional buoyancy in vertical soap films
Adami, Nicolas ULg; Caps, Hervé

in Europhysics Letters [=EPL] (2014)

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See detailAdolescents et délinquance : Quelles représentations de la sexualité et de la pornographie, pour quelle sexualité ?
Puglia, Rosa ULg; Glowacz, Fabienne ULg

Conference (2014, May)

Bien que la pornographie ne soit pas un phénomène nouveau, ses supports, ses modalités d’accès, son public, etc. se sont vus modifiés suite à l’avènement des nouvelles technologies. Ainsi, de nos jours ... [more ▼]

Bien que la pornographie ne soit pas un phénomène nouveau, ses supports, ses modalités d’accès, son public, etc. se sont vus modifiés suite à l’avènement des nouvelles technologies. Ainsi, de nos jours, les adeptes de ce média peuvent d’un simple clic visionner une variété d’images et de films à caractère pornographique de manière anonyme et gratuite. Alors que de nombreuses questions se posent quant à l’influence de ces médias sur le développement psycho-sexuel et sur les conduites des adolescents, peu d’études y ont été consacrées. Avant de considérer la population délinquante, il était important d’évaluer la consommation pornographique dans une perspective développementale auprès d’une population d’adolescents. Nos recherches se sont centrées, d‘une part sur l’impact de l’accessibilité et de la visualisation de ces médias au niveau des représentations de la sexualité et de la pornographie, et d’autre part, sur l’influence de la consommation pornographique au niveau du développement psycho-sexuel et des pratiques sexuelles des adolescents. Une enquête a été menée auprès de 319 jeunes (150 filles) comprenant, en plus des items se rapportant à la sexualité et la pornographie, plusieurs tests évaluant des dimensions du fonctionnement psychologique et social (test de solitude, recherche de sensation, relations aux pairs, délinquance auto-révélée,... ). Des entretiens semi-directifs ainsi que les différents tests ont été proposés à 20 adolescents délinquants judiciarisés. Nos résultats mettent en évidence que la consommation pornographique influence les représentations (et réciproquement) et certains aspects des pratiques sexuelles des jeunes. Il ressort également que les adolescents délinquants (auto-révélés et judiciarisés) apparaissent comme plus vulnérables par rapport aux sollicitations de ces médias. [less ▲]

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See detailVerso il fuorigioco. Una squadra di storie sul calcio
Curreri, Luciano ULg; Comberiati, Daniele

Book published by Il Foglio (2014)

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See detailStructured reflection breaks embedded in an online course – Effects on learning experience, time on task and performance
Verpoorten, Dominique ULg; Westera, Wim

in Interactive Learning Environments (2014)

The purpose of this paper is to gain insight into the effects of practicing short, frequent and structured reflection breaks interspersed with the learning material in a computer-based course. To that end ... [more ▼]

The purpose of this paper is to gain insight into the effects of practicing short, frequent and structured reflection breaks interspersed with the learning material in a computer-based course. To that end, the study sets up a standardised control trial with 2 groups of secondary-school pupils. The study shows that, while performance is not affected by these embedded “reflection rituals”, they significantly impact time on task and perceived learning. The study also suggests that the exposure to such built-in opportunities for reflection modifies the engagement with the content and fosters the claimed readiness for application of a similar reflective approach to learning in other occasions. [less ▲]

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See detailL'intensification des procédés chimiques, une approche radicale
Henneuse, Catherine; Monbaliu, Jean-Christophe ULg

Article for general public (2014)

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See detailL'immatériel en droit international privé - approche belge
Wautelet, Patrick ULg

Scientific conference (2014, May)

Ce rapport a été écrit sur base d'un questionnaire rédigé par le Professeur Tristan Azzi dans le cadre des journées internationales de l'Association Henri Capitant (Barcelone/Madrid 2014). Ce rapport ... [more ▼]

Ce rapport a été écrit sur base d'un questionnaire rédigé par le Professeur Tristan Azzi dans le cadre des journées internationales de l'Association Henri Capitant (Barcelone/Madrid 2014). Ce rapport aborde essentiellement deux questions liées à l'immatériel en droit international privé : le contentieux de la propriété intellectuelle et celui lié à l'usage d'internet. [less ▲]

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See detailVitamin D status of schoolchildren in Northern Algeria, seasonal variations and determinants of vitamin D deficiency
Djennane, M; Lebbah, S; Roux, C et al

in Osteoporosis International (2014), 25(5), 1493-502

Summary There are no published data on the vitamin D status of children living in North Africa. In 435 healthy Algerian children 5–15 years old, we found that vitamin D insufficiency (serum 25 ... [more ▼]

Summary There are no published data on the vitamin D status of children living in North Africa. In 435 healthy Algerian children 5–15 years old, we found that vitamin D insufficiency (serum 25-hydroxyvitamin D (25OHD) <50 nmol/L) was frequent, especially in winter. Low vitamin D status was associated with increased parathyroid hormone (PTH) and leg deformation Introduction As there are no published data on the vitamin D status of children living in North Africa, we evaluated the 25OHD concentration of healthy Algerian children at the end of summer and at the end of winter. As secondary objectives, we studied the various determinants of vitamin D status and the PTH-25OHD relationship in these subjects. Methods Four hundred thirty-five children 5–15 years old were examined and had a blood sample in September 2010. Of them, 408 were sampled again in March 2011. Results Median 25OHD concentration in the whole group was 71.4 nmol/L in September and 52.9 nmol/L in March. In September, 58.4, 29.9, and 8.1 % had a 25OHD concentration below 75, 50, and 30 nmol/L respectively. In March, these percentages increased to 65.2, 41.4, and 17.4 % for the 75, 50, and 30 nmol/L threshold, respectively. In multivariate analysis, older age, darker skin phototype, low daily vitamin D and calcium intake, poor socioeconomic status, and short daily sun exposure remained significantly associated with a 25OHD <50 nmol/L at both visits. In 72 (16.6 %) children, genu varum/valgum was present. Compared to the 363 children without leg deformation, they presented more frequently with the risk factors of vitamin D insufficiency. They also had lower 25OHD concentrations and higher PTH and tALP. Serum PTH and 25OHD concentrations were negatively and significantly correlated (r=−0.43; p<0.001) without a 25OHD threshold above which PTH does not decrease anymore. Conclusion Despite a sunny environment, vitamin D insufficiency is frequent in healthy Algerian children. [less ▲]

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See detailSustainable Resource Availability : Ge, Ni, Al three contrasting stories
Pirard, Eric ULg

Conference (2014, May)

The sustainable availability of raw materials used in manufacturing advanced products is a question that consumers will raise more and more in the future. In order to answer this legitimate request it is ... [more ▼]

The sustainable availability of raw materials used in manufacturing advanced products is a question that consumers will raise more and more in the future. In order to answer this legitimate request it is mandatory to define characterization factors capable of taking into account the geological scarcity of an element but also the social and environmental impact of its exploitation and beneficiation. Recent studies (Vieira et al. 2012; Swart el al. 2013) have focused on decreasing ore grades as rough indicators, but clearly such indicators can be severely biased by breakthrough innovations in mining technologies as well as by high metal prices generated by increasing demand. In this paper, we will briefly review three metals that could technically be extracted from very different social and natural environments: Germanium is nowadays mainly a byproduct of coal burnt in China, but could as well be gained from alternative sources such as zinc sulfides. Aluminium is produced from bauxite with Gallium as a byproduct but could technically be extracted from alternative resources such as regionally available clays. Finally, the world nickel production follows two very different processing routes starting either from silicates (laterite deposits) or from sulfides (ultramafic magmas). By comparing the geological; environmental and social impact of mining operations for these three metals, we will try to show what is hidden behind simple ore grades and what indicators should be taken into account in a more complex analysis of sustainable availability. The intention is to build a geographical information system (GIS) of mineral resources and mining operations to help product manufacturers in properly selecting their raw materials providers. Vieira, M.D.M., Goedkoop, M.J., Storm, P. and Huijbregts, M.A.J., 2012, Ore grade decrease as a life cycle impact indicator for metal scarcity : The case of copper. Environ. Sci. Technol. 46, 12772-12778 Swart, P. and Dewulf, J., 2013, Quantifying the impacts of primary metal resource use in life cycle assessment based on recent mining data. Resources, Conservation and Recycling, 73, 180-187. [less ▲]

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See detailHeterochrony in a complex world: disentangling environmental processes of facultative paedomorphosis in an amphibian
Denoël, Mathieu ULg; Ficetola, Gentile Francesco

in Journal of Animal Ecology (2014), 83(3), 606-615

1. Heterochrony, the change in the rate or timing of development between ancestors and their descendants, plays a major role in evolution. When heterochrony produces polymorphisms, it offers the ... [more ▼]

1. Heterochrony, the change in the rate or timing of development between ancestors and their descendants, plays a major role in evolution. When heterochrony produces polymorphisms, it offers the possibility to test hypotheses that could explain its success across environments. Amphibians are particularly suitable to exploring these questions because they express complex life cycles (i.e. metamorphosis) that have been disrupted by heterochronic processes (paedomorphosis: retention of larval traits in adults). The large phenotypic variation across populations suggests that more complex processes than expected are operating, but they remain to be investigated through multivariate analyses over a large range of natural populations across time. 2. In this study we compared the likelihood of multiple potential environmental determinants of heterochrony. We gathered data on the proportion of paedomorphic and metamorphic palmate newts (Lissotriton helveticus) across more than 150 populations during 10 years, and used an information-theoretic approach to compare the support of multiple potential processes. 3. Six environmental processes jointly explained the proportion of paedomorphs in populations: predation, water availability, dispersal limitation, aquatic breathing, terrestrial habitat suitability, and anti-predator refuges. Analyses of variation across space and time supported models based on the advantage of paedomorphosis in favourable aquatic habitats. 4. Paedomorphs were favoured in deep ponds, in conditions favourable to aquatic breathing (high oxygen content), with lack of fish, and surrounded by suitable terrestrial habitat. Metamorphs were favoured by banks allowing easy dispersal. 5. These results indicate that heterochrony relies on complex processes involving multiple ecological variables and exemplifies why heterochronic patterns occur in contrasted environments. On the other hand, the fast selection of alternative morphs shows that metamorphosis and paedomorphosis developmental modes could be easily disrupted in natural populations. [less ▲]

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See detailThe XMM-Newton view of the yellow hypergiant IRC+10420 and its surroundings
De Becker, Michaël ULg; Hutsemekers, Damien ULg; Gosset, Eric ULg

in New Astronomy (2014), 29

Among evolved massive stars likely in transition to the Wolf-Rayet phase, IRC +10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by ... [more ▼]

Among evolved massive stars likely in transition to the Wolf-Rayet phase, IRC +10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by quite high mass loss episodes. Even though IRC+10420 benefited of many observations in several wavelength domains, it has never been a target for an X-ray observatory. We report here on the very first dedicated observation of IRC+10420 in X-rays, using the XMM-Newton satellite. Even though the target is not detected, we derive X-ray flux upper limits of the order of 1–3 ×10−14 erg cm−2 s−1 (between 0.3 and 10.0 keV), and we discuss the case of IRC+10420 in the framework of emission models likely to be adequate for such an object. Using the Optical/UV Monitor on board XMM-Newton, we present the very first upper limits of the flux density of IRC +10420 in the UV domain (between 1800 and 2250 Å and between 2050 and 2450 Å). Finally, we also report on the detection in this field of 10 X-ray and 7 UV point sources, and we briefly discuss their properties and potential counterparts at longer wavelengths. [less ▲]

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See detailSEDIMENTS OXIDATION BY SEAGRASSES: INFLUENCE ON THE S CYCLE IN POSIDONIA OCEANICA (L.) DELILE INTERMATTES DYNAMIC
Abadie, Arnaud ULg; Lejeune, Pierre; Pergent, Gérard et al

Poster (2014, May)

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of ... [more ▼]

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of sand or dead matte (matte without living shoots) patches, called “intermattes”, which can have natural or anthropogenic origins. Mechanical processes (e. g. currents, anchoring) can initiate intermattes formation but their dynamic after creation seems to be linked with the sediment chemistry, especially with S cycle. P. oceanica plays an important role in controlling coastal belowground biogeochemistry, in particular by oxidizing sediments through the release of O2 by roots. This process allows creating more suitable condition for plant growth and colonization. The lack of H2S oxidation in SO4 2- can lead to limitation of the plant development or its regression. In order to investigate the effect of oxidation condition in sediments on intermattes dynamic and the neighboring meadow, we initiate, in December 2013, a study on six intermattes (three natural, three anthropogenic) at different depths in Calvi Bay, in Corsica (France). We hypothesize that redox potential and H2S concentration in sediments play an important role in the regression of P. oceanica meadows, particularly after a mechanical anthropic impact like anchoring. It also may be possible that two different kinds of processes are involved for each type of intermatte. Regular samplings throughout two years are planed with the aim of evaluating the seasonal variations of physicochemical parameters. [less ▲]

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See detailLes transferts artistiques dans l'Europe gothique. Repenser la circulation des artistes, des oeuvres, des thèmes et des savoir-faire (XIIe - XVIe siècle)
Van den Bossche, Benoît ULg; Guillouët, Jean-Marie; Dubois, Jacques et al

Book published by A. et J. Picard (2014)

Detailed reference viewed: 25 (6 ULg)