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See detailTHE LACTOPEROXIDASE SYSTEM, A NATURAL BIOCHEMICAL BIOCONTROL AGENT FOR PRE- AND POST-HARVEST APPLICATIONS
Bafort, Françoise ULg; Parisi, Olivier ULg; Perraudin, Jean-Paul et al

in Journal of Phytopathology (2017), 165(1), 22-34

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See detailLooking for phosphate-accumulating bacteria in activated sludge processes : a multidisciplinary approach
Tarayre, Cédric ULg; Charlier, Raphaëlle; Delepierre, Anissa ULg et al

in Environmental Science and Pollution Research (2017)

Over the past decades, an increasing need in renewable resources has progressively appeared. This trend concerns not only fossil fuels but also mineral resources. Wastewater and sewage sludge contain ... [more ▼]

Over the past decades, an increasing need in renewable resources has progressively appeared. This trend concerns not only fossil fuels but also mineral resources. Wastewater and sewage sludge contain significant concentrations in phosphate and can be considered as a fertilizer source of the utmost importance. In wastewater treatment plants, the biological uptake of phosphate is performed by a specific microbiota: the phosphate-accumulating organisms. These microorganisms are recovered in sewage sludge. Here, we aimed to investigate the occurrence of phosphate accumulators in four wastewater treatment plants. A 16S metagenetic analysis identified the main bacterial phyla extracted from the aerobic treatment: α-Proteobacteria, β-Proteobacteria, and Sphingobacteria. An enrichment stage was performed to stimulate the specific growth of phosphate-accumulating bacteria in an acetate medium. An analysis of metabolic activities of sulfur and phosphorus highlighted strong modifications related to phosphorus and much less distinguishable effects with sulfur. A solid acetate medium containing 5-Br-4-Cl-3-indolyl phosphate was used to select potential phosphate-accumulating bacteria from the enriched consortia. The positive strains have been found to belong in the genera Acinetobacter, Corynebacterium, and Pseudomonas. Finally, electron microscopy was applied to the strains and allowed to confirm the presence of polyphosphate granules. Some of these bacteria contained granules the size of which exceeded 100 nm. [less ▲]

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See detailImpact of food type on respiration, fractionation and turnover of carbon and nitrogen stable isotopes in the marine amphipod Gammarus aequicauda (Martynov, 1931).
Remy, François ULg; Darchambeau, François ULg; Melchior, Aurélie et al

in Journal of Experimental Marine Biology & Ecology (2017), 486

This study experimentally determined the impact of food source type on turnover rate and trophic enrichment factors (TEFs or ∆) of δ13C and δ15N, as well as on respiration rate, in captive populations of ... [more ▼]

This study experimentally determined the impact of food source type on turnover rate and trophic enrichment factors (TEFs or ∆) of δ13C and δ15N, as well as on respiration rate, in captive populations of the marine amphipod Gammarus aequicauda. Gammarus aequicauda (318 individuals) were fed ad libitum with three food sources animal, algae, and dead Posidonia oceanica leaves (also called “litter”), varying in palatability, digestibility, nutritional qualities and isotopic compositions, for between four and six weeks in a controlled feeding experiment. The resulting death rate was lower for the amphipods fed with animal treatment (30.9%) than for individuals fed with algal (65.9%) or litter treatment (64.4%), indicating a better fitness of the individuals fed with the animal food source. Respiration rates also differed highly among the treatments. Animal treatment showed higher respiration rates than algal and litter treatments, potentially due to the toxicity of the algae and the very low nutritional quality of the litter. Amphipods fed with these treatments might have entered in a “low activity state” to cope with these unsuitable food sources, inducing low respiration rates. Due to the very low assimilation and toxicity of the algae source, turnover rate for δ13C was impossible to determine. Turnover rate for δ13C was much faster (half-life = 12.55 days) for amphipods fed with the animal food source than for amphipods fed with litter (half-life = 51.62 days), showing the faster assimilation of the most nutritionally optimal food sources by G. aequicauda. Turnover for δ15N was impossible to determine because the amphipods were already at isotopic equilibrium at the beginning of the experiment. Despite the detritus feeder status of Gammarus aequicauda, TEFs for the animal treatments were in accordance with values generally found for carnivorous organisms (∆13C = 0.9 ± 0.7‰; ∆15N = 2.9 ± 0.6‰). TEFs for the litter treatment were in accordance with values generally corresponding to detritivorous organisms (∆13C = 1.2‰; ∆15N = 1.0 ± 0.4‰). SIAR mixing model outputs obtained with these new TEF values were more constrained and coherent than outputs obtained with general literature TEFs. This study thus demonstrated the non-negligible impact of the food source on Gammarus aequicauda physiological status, fitness and turnover rates, but also on TEFs—highlighting the importance of TEF experimental calculations for every potential food source of a given organism to ensure more robust isotopic data interpretation. [less ▲]

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See detailMethane balance of an intensively grazed pasture and estimation of the enteric methane emissions from cattle
Dumortier, Pierre ULg; Aubinet, Marc ULg; Beckers, Yves ULg et al

in Agricultural and Forest Meteorology (2017), 232

The methane turbulent fluxes of an intensively grazed pasture were measured continuously from June 2012 to December 2013 at the Dorinne Terrestrial Observatory (DTO) in Belgium. During grazing periods ... [more ▼]

The methane turbulent fluxes of an intensively grazed pasture were measured continuously from June 2012 to December 2013 at the Dorinne Terrestrial Observatory (DTO) in Belgium. During grazing periods, the fluxes were dominated by enteric fermentation and were found to be strongly related to cow stocking density. In 2013, total emission from the pasture was found between 9 and 11 g CH4 m−2, 97% of which being emitted during grazing periods. Emission per LU (livestock unit) was estimated in a non-invasive way by integrating eddy covariance fluxes over large periods and by assuming a homogeneous average cattle disposition on the pasture. This estimate was compared to the one obtained during confinement periods, where cows were confined in a small part of the pasture. The emission per LU varied between 104 and 134 g CH4 LU−1 day−1 (13 and 17 g CH4 kg DMI−1), depending on the dataset and the computation method used. Diel course was characterized by two emission peaks, one in the morning and a larger one in the afternoon. For rest periods (no cattle on the pasture), small emissions were observed (median and mean values of 0.5 and 1.5 mg CH4 m−2 day−1, respectively). [less ▲]

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See detailThermal history modelling to understand microstructures observed in repair technology of Ti-6Al-4V
Tran, Hoang Son ULg; Tchuindjang, Jérôme Tchoufack ULg; Hakan, Paydas et al

in Extended Abstract book of 14th Conf. on Computer Methods in Materials Technology KomPlasTech 2017 (2017, January)

Laser cladding is a metal deposition technique used to fabricate or repair components. In the present work Ti-6Al-4V deposits with a variable thickness are studied to assess the use of laser cladding as a ... [more ▼]

Laser cladding is a metal deposition technique used to fabricate or repair components. In the present work Ti-6Al-4V deposits with a variable thickness are studied to assess the use of laser cladding as a repair technology [1]. Solidification following melting and partial remelting of pre-existing layers is coupled with heat treatment of the solidified material due to the repeated heating and cooling cycles during building. The effect of the building strategy on the metallurgical characteristics of the material for a decreasing track length (DTL) or a constant track length (CTL) strategy is analyzed. Depending on the possible heat accumulation, the nature of the phases are determined by metallography and hardness maps of the deposits. Optical Microscopy (OM), Stereo Microscopy (SM), and Scanning Electron Microscopy (SEM) were used in order to study the microstructure. The generation of the microstructure results from the material thermal history. This one is computed by Finite Element Method and a careful analysis establishes the link between the phase state and the detailed thermal history. [less ▲]

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See detailQuelques idées générales à propos de la compréhension en mathématiques
Bair, Jacques ULg

E-print/Working paper (2017)

Dans cet article, nous apportons des éléments de réponse à la question générale suivante : "Que signifie bien comprendre en mathématiques ?" Nous nous demandons pourquoi il est difficile d'y répondre et ... [more ▼]

Dans cet article, nous apportons des éléments de réponse à la question générale suivante : "Que signifie bien comprendre en mathématiques ?" Nous nous demandons pourquoi il est difficile d'y répondre et apportons une piste de solution en distinguant les activités de production de celles de reproduction. De plus, nous abordons le problème étudié d'un point de vue aussi bien local que global. Enfin, nous nous interrogeons sur l'incompréhension en mathématiques en proposant une typologie, en repérant des causes possibles d'incompréhension et en donnant quelques conseils pratiques. [less ▲]

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See detailRelevance of vitamin D in the pathogenesis and therapy of frailty.
Bruyère, Olivier ULg; Cavalier, Etienne ULg; Buckinx, Fanny ULg et al

in Current Opinion in Clinical Nutrition & Metabolic Care (2017), 20(1), 26-29

PURPOSE OF REVIEW: This article reviews recently published evidence regarding the role of vitamin D in the physiopathology of physical frailty in elderly populations and its role in the management of this ... [more ▼]

PURPOSE OF REVIEW: This article reviews recently published evidence regarding the role of vitamin D in the physiopathology of physical frailty in elderly populations and its role in the management of this geriatric condition. RECENT FINDINGS: Some recent studies have found a low level of 25-hydroxyvitamin D, considered the best marker of vitamin D status, in frail individuals. All prospective studies consistently report that low vitamin D status is associated with an increased risk of becoming frail. Recent studies also suggest that the relationship between vitamin D status and frailty is largely mediated by the development of sarcopenia. Very few well designed randomized controlled trials are available that assess the effectiveness of vitamin D supplementation in the prevention or management of frailty. In the absence of specific guidelines, a minimal serum 25-hydroxyvitamin D level of 75 nmol/l is proposed for frail elderly patients by some scientific societies. The doses necessary to reach this target are between 800 and 2000 IU/day. SUMMARY: Several studies suggest a potential effect of vitamin D on physical frailty but large clinical trials are lacking at this time to provide solid evidence of clinical benefit. [less ▲]

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See detailUn « Laboratoire belge » du droit international (1869-1940) ? Réseaux internationaux, expériences et mémoires de guerre des juristes belges
Genin, Vincent ULg

Doctoral thesis (2017)

Circonscrire une problématique implique de dégager plusieurs hypothèses de travail. La Première Guerre mondiale représente le pivot autour duquel ces hypothèses s’articuleront et seront mises à l’épreuve ... [more ▼]

Circonscrire une problématique implique de dégager plusieurs hypothèses de travail. La Première Guerre mondiale représente le pivot autour duquel ces hypothèses s’articuleront et seront mises à l’épreuve. Celle-ci étant destinée à les « mettre à l’épreuve ». À l’issue de ce travail, nous espérons que la confrontation de ces hypothèses à l’analyse historique permettra la décantation de conclusions générales dont émanera une thèse définie. La Guerre de 1914-1918, par son caractère global, ses « innovations » technologiques, son degré de violence, marque une étape significative de l’histoire contemporaine. La Belgique, premier pays du front Ouest à être envahi, se situe aux premières loges de cette nouvelle phase historique. Territoire dont la neutralité « perpétuelle, permanente et garantie » est violée, en transgression du droit international public, ce point d’ancrage semble propice à l’étude d’un milieu ayant peu attiré l’attention des historiens : les juristes belges de droit international. Nous estimons que cette étude est à même de mieux nous informer sur les caractéristiques de ce milieu professionnel en soi, concerné au premier chef par l’acte inaugural de la guerre, sur ses pratiques, ses codes, ses réseaux internationaux, la positionnalité des juristes, mais aussi, en négatif, de nous renseigner sur un aspect méconnu de l’image de la Belgique et de sa position dans la hiérarchie internationale, à savoir sa contribution au droit international. L’évolution de ce milieu et de ce qu’il représente, à l’aune de la Guerre de 1914-1918, reconnue pour avoir acceléré la juridicisation des relations internationales, constitue l’essentiel de l’angle d’approche adopté par notre recherche. Toutefois, il est permis de dégager plusieurs hypothèses, dont chacune recouvre un critère de cette approche plus générale : En effet, le conflit modifie-t-il le degré de légitimité de cette catégorie de juristes dans le champ scientifique belge et exerce-t-il une influence similaire dans le champ académique ? Dans quelle mesure les internationalistes belges jouent-ils un nouveau rôle, après 1918, dans le cadre de la politique étrangère officielle du pays ? Par extension, nous nous intéresserons à leur rapport au milieu des diplomates. Nous tenterons également d’évaluer dans quelle mesure ces juristes sont les acteurs d’un phénomène transnational ou, au contraire, s’ils poursuivent des objectifs dont les intérêts sont « nationaux ». Par ailleurs, ces juristes peuvent-ils être considérés comme des indicateurs, des pierres de touche, de l’évolution de la position de la Belgique dans le « Concert des nations » ? Le cas échéant, nous tenterons de comprendre dans quelle mesure cette « condition » d’indicateur évolue entre l’avant-1914 et l’après-1918. Ces juristes contribuent-ils à la défense d’enjeux idéologiques et/ou politiques et comment se positionnent-ils par rapport aux conceptions jusnaturalistes et juspositivistes ? À l’aune des réflexions précédentes, il est possible d’envisager une problématique générale, que l’on peut énoncer comme suit : Dans quelle mesure les juristes belges de droit international public, de la fin du XIXème siècle au milieu du XXème siècle, ont tissé des réseaux internationaux, été des indicateurs de l’évolution de la Belgique dans la hiérarchie internationale et, surtout, ont été influencés par l’expérience de la Guerre de 1914-1918, en tant que génératrice d’une mémoire influant sur les modes d’expressions et de représentations de ce groupe social, jusqu’en 1940. [less ▲]

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See detailCharacteristics of EoL Printed Wiring Boards processed by ElectroDynamic Fragmentation
Martino, Rémi ULg; Iseli, Cedric; Gaydardzhiev, Stoyan ULg et al

in Chemie Ingenieur Technik (2017), 89(1-2), 1-10

The ElectroDynamic Fragmentation (EDF) is an innovative technique which enables selective fragmentation of material. Its inherent selective breakage principles enable liberation while avoiding fine ... [more ▼]

The ElectroDynamic Fragmentation (EDF) is an innovative technique which enables selective fragmentation of material. Its inherent selective breakage principles enable liberation while avoiding fine grinding. In this study, the specific effects of the EDF on End-of-Life Printed Wiring Boards have been assessed. A novel methodology for their EDF processing has been developed and compared with hammer mill shredding. Various energy inputs and treatment stages have resulted in fragmentation degrees ranging from removal of components to structure delamination and subsequent size reduction. [less ▲]

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See detailAttention et simultanéité intellectuelle chez Descartes, Clauberg et Spinoza
Dubouclez, Olivier ULg

in Les études philosophiques (2017), 1

Abstract. – is paper deals with a classical problem, can we think or apprehend many things at once ? as it was understood and solved by Descartes and its followers. e idea that we can apprehend di erent ... [more ▼]

Abstract. – is paper deals with a classical problem, can we think or apprehend many things at once ? as it was understood and solved by Descartes and its followers. e idea that we can apprehend di erent ideas at once is central in Descartes’ theory of knowledge, especially in the Rules, and it relies on the claim that attention can be divided between two objects or ideas. Clauberg considers on the contrary that the imagination alone can graps things simultaneously and holds the living body as the true paradigm of simultaneous activity. Spinoza has a synthetic point of view : simultaneity within the body and the mind are expressions of the power of the individ- ual and of his develoment. Attention is no more a condition of intellectual simultaneity, as in Descartes, but is rather an obstacle which needs to be overcome to reach a richer and better understanding of reality. [less ▲]

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See detailLinking pollutant exposure of humpback whales breeding in the Indian Ocean to their feeding habits and feeding areas off Antarctica
Das, Krishna ULg; Malarvannan, Govindan; Dirtu, Alin et al

in Environmental Pollution (2017), 220

Humpback whales, Megaptera novaeangliae, breeding off la Reunion Island (Indian Ocean) undergo large-scale seasonal migrations between summer feeding grounds near Antarctica and their reproductive winter ... [more ▼]

Humpback whales, Megaptera novaeangliae, breeding off la Reunion Island (Indian Ocean) undergo large-scale seasonal migrations between summer feeding grounds near Antarctica and their reproductive winter grounds in the Indian Ocean. The main scope of the current study was to investigate chemical exposure of humpback whales breeding in the Indian Ocean by providing the first published data on this breeding stock concerning persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), DDT and its metabolites (DDTs), chlordane compounds (CHLs), polybrominated diphenyl ethers (PBDEs), and methoxylated PBDEs (MeO-PBDEs). Analyses of stable isotopes δ13C and δ15N in skin resulted in further insight in their feeding ecology, which was in agreement with a diet focused mainly on low trophic level prey species, such as krill from Antarctica. POPs were measured in all humpback whales in the order of HCB > DDTs > CHLs > HCHs > PCBs > PBDEs > MeO-BDEs. HCB (median: 24 ng.g-1 lw) and DDTs (median: 7.7 ng.g-1 lw) were the predominant compounds in all whale biopsies. Among DDT compounds, p,p’-DDE was the major organohalogenated pollutant, reflecting its long-term accumulation in humpback whales. Significantly lower concentrations of HCB and DDTs were found in females than in males (p<0.001). Other compounds were similar between the two genders (p>0.05). Differences in the HCB and DDTs suggested gender-specific transfer of some compounds to the offspring. POP concentrations were lower than previously reported results for humpback whales sampled near the Antarctic Peninsula, suggesting potential influence of their nutritional status and may indicate different exposures of the whales according to their feeding zones. Further investigations are required to assess exposure of southern humpback whales throughout their feeding zones. [less ▲]

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See detailSpatial variation in the accumulation of POPs and mercury in bottlenose dolphins of the Lower Florida Keys and the coastal Everglades (South Florida)
Damseaux, France ULg; Kiszka, J.; Heithaus, M.R. et al

in Environmental Pollution (2017), 220

The bottlenose dolphin (Tursiops truncatus) is an upper trophic level predator and the most common cetacean species found in nearshore waters of southern Florida, including the Lower Florida Keys (LFK ... [more ▼]

The bottlenose dolphin (Tursiops truncatus) is an upper trophic level predator and the most common cetacean species found in nearshore waters of southern Florida, including the Lower Florida Keys (LFK) and the Florida Coastal Everglades (FCE). The objective of this study was to assess contamination levels of total mercury (T-Hg) in skin and persistent organic pollutants (PCBs, PBDEs, DDXs, HCHs, HCB, Σ PCDD/Fs and Σ DL-PCBs) in blubber samples of bottlenose dolphins from LFK (n = 27) and FCE (n = 24). PCBs were the major class of compounds found in bottlenose dolphin blubber and were higher in individuals from LFK (Σ 6 PCBs LFK males: 13421 ± 7730 ng.g-1 lipids, Σ 6 PCBs LFK females: 9683 ± 19007 ng.g-1 lipids) than from FCE (Σ 6 PCBs FCE males: 5638 ng.g-1 ± 3627 lipids, Σ 6 PCBs FCE females: 1427 ± 908 ng.g-1 lipids). These levels were lower than previously published data from the southeastern USA. The Σ DL-PCBs were the most prevalent pollutants of dioxin and dioxin like compounds (Σ DL-PCBs LFK: 739 ng.g-1 lipids, Σ DL-PCBs FCE: 183 ng.g-1 lipids) since PCDD/F concentrations were low for both locations (mean 0.1 ng.g-1 lipids for LFK and FCE dolphins). The toxicity equivalences of PCDD/Fs and DL-PCBs expressed as TEQ in LFK and FCE dolphins is mainly expressed by DL-PCBs (81% LFK - 65% FCE). T-Hg concentrations in skin were significantly higher in FCE (FCE median 9314 ng.g-1 dw) compared to LFK dolphins (LFK median 2941 ng.g-1 dw). These bottlenose dolphins concentrations are the highest recorded in the southeastern USA, and may be explained, at least partially, by the biogeochemistry of the Everglades and mangrove sedimentary habitats that create favourable conditions for the retention of mercury and make it available at high concentrations for aquatic predators. [less ▲]

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See detailTracing Migrant-Mothers’ ‘Return’ Narratives in the Mexico-U.S and Peru-Belgium Migratory Circuits.
Vivas Romero, Maria ULg; Sanchez-Martinez, Anabela

in Travaux et recherches dans les amériques du centre (2017)

How do contemporary migrant mothers strategize return to their home countries? And how does the social protections available for their bi-national children in sending and destination countries factor in ... [more ▼]

How do contemporary migrant mothers strategize return to their home countries? And how does the social protections available for their bi-national children in sending and destination countries factor in the decision to return? Through this contribution, we aimed to tackle these questions. We draw from the analysis of two longitudinal migratory careers and argue that our participant’s return decisions were influenced both by their children’s effective access to social protection and their subjective perceptions of ‘good-motherhood’. This Trans-Atlantic comparison shows how different situated-institutional-contexts, cultures of care and motherhood resulted into different patterns of mobility for these women and their families. [less ▲]

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See detailLa «Health Literacy»,un moyen pour réduire les inégalités sociales de santé
Bragard, Isabelle ULg; COUCKE, Philippe ULg; Pétré, Benoît ULg et al

in Revue Médicale de Liège (2017), 72(1),

Health literacy (HL) is defined as ‘the knowledge, motivation, and competences to access, understand, appraise and apply health information in order to make judgments and take decisions in everyday life ... [more ▼]

Health literacy (HL) is defined as ‘the knowledge, motivation, and competences to access, understand, appraise and apply health information in order to make judgments and take decisions in everyday life concerning health care, disease prevention and health promotion to maintain or improve quality of life’. This concept begins to be recognized as a priority area for action at political level in Belgium. Indeed, a limited HL may affect health by leading, by example, with poorer management of chronic diseases, more hospital admissions and premature deaths. This paper addresses the question of HL evaluation, improvement interventions as well as the many challenges that remain in this area. HL seems fundamental to the development of better health management. It would allow patients to play a more active role in health care, to involve all health stakeholders, and to contribute to a more sustainable health system. Improving HL could allow better equal access to health care. [less ▲]

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See detailMorphology of the filtration apparatus of three planktivorous fishes and relation with ingested anthropogenic particles
Collard, France ULg; Gilbert, Bernard ULg; Eppe, Gauthier ULg et al

in Marine Pollution Bulletin (2017)

Anthropogenic particles (APs), including microplastics, are ingested by a wide variety of marine organisms. Exposure of Clupeiformes (e.g. herrings, anchovies, sardines) is poorly studied despite their ... [more ▼]

Anthropogenic particles (APs), including microplastics, are ingested by a wide variety of marine organisms. Exposure of Clupeiformes (e.g. herrings, anchovies, sardines) is poorly studied despite their economic and ecological importance. This study aims to describe the morphology of the filtration apparatus of three wild-caught Clupeiformes (Sardina pilchardus, Clupea harengus and Engraulis encrasicolus) and to relate the results to ingested APs. Consequently, the species with the more efficient filtration apparatus will be more likely to ingest APs. We hypothesized that sardines were the most exposed species. The filtration area and particle retention threshold were determined in the three species, with sardines displaying the highest filtration area and the closest gill rakers. Sardines ingested more fibers and smaller fragments, confirming that it is the most efficient filtering species. These two results lead to the conclusion that, among the three studied, the sardine is the species most exposed to APs. [less ▲]

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See detailGREDOR. Outcomes and recommendations
Cornélusse, Bertrand ULg; Ernst, Damien ULg

Report (2017)

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See detailA Machine Learning-Based Approximation of Strong Branching
Marcos Alvarez, Alejandro ULg; Louveaux, Quentin ULg; Wehenkel, Louis ULg

in INFORMS Journal on Computing (2017), 29(1), 185-195

We present in this paper a new generic approach to variable branching in branch-and-bound for mixed- integer linear problems. Our approach consists in imitating the decisions taken by a good branching ... [more ▼]

We present in this paper a new generic approach to variable branching in branch-and-bound for mixed- integer linear problems. Our approach consists in imitating the decisions taken by a good branching strategy, namely strong branching, with a fast approximation. This approximated function is created by a machine learning technique from a set of observed branching decisions taken by strong branching. The philosophy of the approach is similar to reliability branching. However, our approach can catch more complex aspects of observed previous branchings in order to take a branching decision. The experiments performed on randomly generated and MIPLIB problems show promising results. [less ▲]

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See detailAssessment of vitamin D status - a changing landscape.
Herrmann, Markus; Farrell, Christopher-John L.; Pusceddu, Irene et al

in Clinical Chemistry & Laboratory Medicine (2017)

In recent years it has been shown that vitamin D deficiency is associated with an increased incidence as well as the progression of a broad range of diseases including osteoporosis, rickets ... [more ▼]

In recent years it has been shown that vitamin D deficiency is associated with an increased incidence as well as the progression of a broad range of diseases including osteoporosis, rickets, cardiovascular disease, autoimmune disease, multiple sclerosis and cancer. Consequently, requests for the assessment of vitamin D status have increased dramatically. Despite significant progress in the analysis of vitamin D metabolites and an expansion of our pathophysiological knowledge of vitamin D, the assessment of vitamin D status remains a challenging and partially unresolved issue. Current guidelines from scientific bodies recommend the measurement of 25-hydroxy vitamin D (25-OHD) in blood as the preferred test. However, growing evidence indicates significant limitations of this test, including analytical aspects and interpretation of results. In addition, the relationships between 25-OHD and various clinical indices, such as bone mineral density and fracture risk, are rather weak and not consistent across races. Recent studies have systematically investigated new markers of vitamin D status including the vitamin D metabolite ratio (VMR) (ratio between 25-OHD and 24,25-dihydroxy vitamin D), bioavailable 25-OHD [25-OHD not bound to vitamin D binding protein (DBP)], and free 25-OHD [circulating 25-OHD bound to neither DBP nor albumin (ALB)]. These parameters may potentially change how we will assess vitamin D status in the future. Although these new biomarkers have expanded our knowledge about vitamin D metabolism, a range of unresolved issues regarding their measurement and the interpretation of results prevent their use in daily practice. It can be expected that some of these issues will be overcome in the near future so that they may be considered for routine use (at least in specialized centers). In addition, genetic studies have revealed several polymorphisms in key proteins of vitamin D metabolism that affect the circulating concentrations of vitamin D metabolites. The affected proteins include DBP, 7-dehydrocholesterol synthase and the vitamin D receptor (VDR). Here we aim to review existing knowledge regarding the biochemistry, physiology and measurement of vitamin D. We will also provide an overview of current and emerging biomarkers for the assessment of vitamin D status, with particular attention methodological aspects and their usefulness in clinical practice. [less ▲]

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