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See detailPresent-day central African forest is a legacy of the 19th century human history
Morin, Julie ULg; Fayolle, Adeline ULg; Favier, Charly et al

in eLife (2017)

The populations of light-demanding trees that dominate the canopy of central African forests are now aging. Here, we show that the lack of regeneration of these populations began ca. 165 ya (around 1850 ... [more ▼]

The populations of light-demanding trees that dominate the canopy of central African forests are now aging. Here, we show that the lack of regeneration of these populations began ca. 165 ya (around 1850) after major anthropogenic disturbances ceased. Since 1885, less itinerancy and disturbance in the forest has occurred because the colonial administrations concentrated people and villages along the primary communication axes. Local populations formerly gardened the forest by creating scattered openings, which were sufficiently large for the establishment of light-demanding trees. Currently, common logging operations do not create suitable openings for the regeneration of these species, whereas deforestation degrades landscapes. Using an interdisciplinary approach, which included paleoecological, archaeological, historical, and dendrological data, we highlight the long-term history of human activities across central African forests and assess the contribution of these activities to present-day forest structure and composition. The conclusions of this sobering analysis present challenges to current silvicultural practices and to those of the future. [less ▲]

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See detailFlexible Bayesian Models for Interval-Censored Survival Data
Cetinyürek, Aysun ULg

Doctoral thesis (2017)

Interval-censored time-to-event data arise frequently in clinical trials and longitudinal studies, where the event of interest is only known to have occurred between the two consecutive visits. Interval ... [more ▼]

Interval-censored time-to-event data arise frequently in clinical trials and longitudinal studies, where the event of interest is only known to have occurred between the two consecutive visits. Interval-censoring is a natural generalization of right censored time-to-event data. For right-censored data, extensive number of statistical techniques are available to tackle most research questions under a variety of assumptions. However, for interval-censored data, less well developed procedures are available. A sparse offer in statistical softwares to handle this type of censoring has driven many researchers to use imputation techniques, especially right-point or mid-point imputation. However such imputation strategies can lead to misleading inferences. Our thesis proposes and studies the properties of innovative methods to analyze such data. In the first part of the text, we have extended a Bayesian density estimation procedure for grouped data to estimate hazard ratios and survival functions from interval-censored data. If one further assumes proportionality of the hazards, the proposed strategy also provides estimates of global covariate effects. Clearly, the proposed method provides very good estimates for the regression coefficients and successfully approximates the baseline survival function when the mean interval width is smaller than some threshold defined from the data standard deviation. In a Cox proportional hazards model, the observations are assumed to be independent. However, this may not be true in certain situations where the observed units are clustered or subject to multiple measurements. A number of approaches generalizing Cox's PH model to handle correlated interval-censored data have been proposed in the literature. The shared frailty model is a popular tool to analyze correlated right-censored time-to-event data. Frailty models have also been adapted to handle interval-censored data. In the case of interval-censored time-to-event data, the inclusion of frailties results in complicated intractable likelihoods. In the second part of this thesis, we propose flexible frailty models for analyzing such data by assuming a smooth flexible form for the conditional time-to-event distribution and a parametric or a flexible form for the frailty distribution. It has been indicated in the literature in different contexts that the misspecification of the random effect distribution can influence the estimation of quantities of primary interest, like the fixed effects. To circumvent such misspecification, we have suggested modeling the distribution of the frailty in a flexible way using P-splines or a gamma shape mixture (GSM) distribution. The biggest advantage of using a flexible specification for the density of frailty arises when its shape is of specific interest. If it is considered as a nuisance, assuming a simpler lognormal or gamma frailty would be an adequate solution to draw conclusions related to other model parameters, such as regression coefficients and variance of frailties. Indeed, it was shown in the simulation study that the regression parameter estimates in a shared frailty PH model are robust to the misspecification of the frailty density. Moreover the use of a flexible form for the frailty does not cause any loss of precision in the estimation of regression parameters when compared to the simpler parametric frailty model. Both models provide the possibility to visualize the baseline density and survival functions. Given sufficiently large sample sizes, the flexible approach produces smooth and accurate posterior estimates for the baseline survival function and for the frailty density, and can correctly detect and identify unusual frailty density forms. [less ▲]

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See detailGlobal UV Imaging by MAVEN/IUVS: Diurnal Cloud Formation, Dust Storms and Atmospheric Scattering.
Schneider; Deighan; Jain et al

Conference (2017, January 17)

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See detailThree Types of Aurora observed by MAVEN/IUVS: Implications for Mars’ upper Atmosphere Energy Budget
Connour; Schneider; Jain et al

Poster (2017, January 17)

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See detailIs Büchi's theorem useful for you? (for an audience of logicians)
Rigo, Michel ULg

Conference (2017, January 17)

Almost a century ago, Presburger showed that the first order theory of the natural numbers with addition is decidable. Following the work of B\"uchi in 1960, this result still holds when adding a function ... [more ▼]

Almost a century ago, Presburger showed that the first order theory of the natural numbers with addition is decidable. Following the work of B\"uchi in 1960, this result still holds when adding a function $V_k$ to the structure, where $V_k(n)$ is the largest power of $k\ge 2$ diving $n$. In particular, this leads to a logical characterization of the $k$-automatic sequences. During the last few years, many applications of this result have been considered in combinatorics on words, mostly by J. Shallit and his coauthors. In this talk, we will present this theorem of B\"uchi where decidability relies on finite automata. Then we will review some results about automatic sequences or morphic words that can be proved automatically (i.e., the proof is carried on by an algorithm). Finally, we will sketch the limitation of this technique. With a single line formula, one can prove automatically that the Thue-Morse word has no overlap but, hopefully, not all the combinatorial properties of morphic words can be derived in this way. We will not assume any background in combinatorics on words from the audience. [less ▲]

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See detailHigh-throughput expression of animal venom toxins in Escherichia coli to generate a large library of oxidized disulphide-reticulated peptides for drug discovery
Turchetto; Sequeira, Ana Filipa; Ramond, Laurie et al

in Microbial Cell Factories (2017), 16(6), 1-15

Animal venoms are complex molecular cocktails containing a wide range of biologically active disulphide-reticulated peptides that target, with high selectivity and efficacy, a variety of membrane ... [more ▼]

Animal venoms are complex molecular cocktails containing a wide range of biologically active disulphide-reticulated peptides that target, with high selectivity and efficacy, a variety of membrane receptors. Disulphide-reticulated peptides have evolved to display improved specificity, low immunogenicity and to show much higher resistance to degradation than linear peptides. These properties make venom peptides attractive candidates for drug development. However, recombinant expression of reticulated peptides containing disulphide bonds is challenging, especially when associated with the production of large libraries of bioactive molecules for drug screening. To date, as an alternative to artificial synthetic chemical libraries, no comprehensive recombinant libraries of natural venom peptides are accessible for high-throughput screening to identify novel therapeutics. RESULTS: In the accompanying paper an efficient system for the expression and purification of oxidized disulphide-reticulated venom peptides in Escherichia coli is described. Here we report the development of a high-throughput automated platform, that could be adapted to the production of other families, to generate the largest ever library of recombinant venom peptides. The peptides were produced in the periplasm of E. coli using redox-active DsbC as a fusion tag, thus allowing the efficient formation of correctly folded disulphide bridges. TEV protease was used to remove fusion tags and recover the animal venom peptides in the native state. Globally, within nine months, out of a total of 4992 synthetic genes encoding a representative diversity of venom peptides, a library containing 2736 recombinant disulphide-reticulated peptides was generated. The data revealed that the animal venom peptides produced in the bacterial host were natively folded and, thus, are putatively biologically active. CONCLUSIONS: Overall this study reveals that high-throughput expression of animal venom peptides in E. coli can generate large libraries of recombinant disulphide-reticulated peptides of remarkable interest for drug discovery programs. [less ▲]

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See detailDiversity and carbon storage across the tropical forest biome
Sullivan, Martin J.P.; Talbot, Joey; Lewis, Simon L. et al

in Scientific Reports (2017), 7(39102),

Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation ... [more ▼]

Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-Tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1 ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity. [less ▲]

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See detailLes institutions politiques belges
Grandjean, Geoffrey ULg

Learning material (2017)

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See detailLeidenfrost effect at its limits
Maquet, Laurent ULg

Doctoral thesis (2017)

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See detailNO Nightglow studies status
Stiepen, Arnaud ULg; Jain; Deighan et al

Conference (2017, January 16)

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See detailLa théorie du complot : un moyen pour expliquer le monde !
Debras, François ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 30 (2 ULg)
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See detailPrésentation de cas cliniques
WANG, François-Charles ULg

Scientific conference (2017, January 16)

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See detailRôles et fonctions des intermédiaires du marché du travail sécurisant les transitions professionnelles
Lorquet, Nadège ULg

Doctoral thesis (2017)

Dans un marché du travail en constante évolution, la flexibilité des emplois et les trajectoires des travailleurs semblent être des sujets incontournables lors de l’étude des organisations. Simultanément ... [more ▼]

Dans un marché du travail en constante évolution, la flexibilité des emplois et les trajectoires des travailleurs semblent être des sujets incontournables lors de l’étude des organisations. Simultanément, de plus en plus de travaux s’intéressent aux rôles des intermédiaires du marché du travail et aux fonctions jouées par ceux-ci à l’intersection entre marché et organisations et entre organisations et travailleurs. Peu de travaux cependant ont cherché explicitement à rapprocher ces deux sujets de recherche, c’est-à-dire à étudier spécifiquement les rôles des intermédiaires du marché du travail sécurisant les trajectoires professionnelles. La présente thèse propose de s’y consacrer. Pour ce faire, douze dispositifs ont été sélectionnés pour leur qualité d’intermédiaire visant à sécuriser les transitions des travailleurs sur le marché du travail. Chacun a fait l’objet d’une étude de cas approfondie, menant à l’élaboration d’une grille d’analyse multidimensionnelle et originale capable de comparer ces dispositifs entre eux. Construite sur base de six critères de différenciation, chacun divisé en trois modalités, la matrice permet de distinguer deux types-idéaux, le « quasi-salarié » et le « quasi-indépendant », caractérisant deux modèles d’intermédiation distincts dont peuvent bénéficier les travailleurs accompagnés lors de leurs transitions. Emergeant d’un processus abductif important, la grille d’analyse multidimensionnelle mobilise de nombreuses références théoriques provenant de diverses disciplines (gestion, droit, économie, sociologie, etc.). Cette thèse s’inscrivant néanmoins en gestion, elle commence par démontrer les principales mutations du marché du travail liées aux organisations, aux carrières et à l’emploi avant d’étudier divers concepts relatifs aux marchés transitionnels du travail et aux intermédiaires également repris sous l’appellation de « Labour Market Intermediaries, LMIs ». [less ▲]

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See detailCryopreservation of chicken primordial germ cells by vitrification and slow-freezing: a comparative study
Tonus, Céline ULg; Connan, Delphine ULg; Waroux, Olivier ULg et al

in Theriogenology (2017), 88

In the present study, we compare a classical slow freezing method and an aseptic vitrification technique to cryopreserve a stable Primordial Gem Cells (PGCs) line issued from the Ardennaise chicken breed ... [more ▼]

In the present study, we compare a classical slow freezing method and an aseptic vitrification technique to cryopreserve a stable Primordial Gem Cells (PGCs) line issued from the Ardennaise chicken breed. Viability immediately after warming was close to 80% and did not differ between the two cryopreservation methods. Proliferation tended to be slower for both cryopreservation methods compared to controls, but the difference was significant only for vitrification. No difference was found between the two methods after flow cytometry analysis of SSEA-1 expression and RT-PCR on several factors related to PGCs phenotype. After one week in culture, all cryopreserved cells reached controls main morphological and expanding (viability/proliferation) features. However, slow freezing generated more unwanted cells clusters than vitrification. After injection of the PGCs into recipient embryos, vitrified PGCs showed a clear, yet not significant, tendency to colonize the gonad at a higher rate than slow frozen PGCs. Slow freezing in cryovials remains simple, inexpensive and less technically demanding than vitrification. Nevertheless, the intrinsic advantages of our aseptic vitrification method and the present study suggest that this should be considered as safer than classical slow freezing for cryopreserving chicken PGCs. [less ▲]

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See detailStudy on reproductive performance of Holstein x Lai Sind crossbred heifers and cows at smallholdings in Ho Chi Minh City, Vietnam.
Nguyen-Kien, Cuong; Nguyen, Van Khanh; Hanzen, Christian ULg

in Tropical Animal Health and Production (2017), 49

The reproductive performance of Holstein x Lai Sind crossbred dairy heifers and cows was evaluated at small-holdings in Ho Chi Minh City (HCMC). The data of 232 heifers and 244 cows (261 lactations) from ... [more ▼]

The reproductive performance of Holstein x Lai Sind crossbred dairy heifers and cows was evaluated at small-holdings in Ho Chi Minh City (HCMC). The data of 232 heifers and 244 cows (261 lactations) from 35 small dairy farms was collected over a 2-year period, from 2013 to 2014. The overall mean for age at first service (AFS), days between first and last service (DFLS), and age at conception (AC) of heifers was 479 (±80), 38 (±80), and 517 (±114) days, respectively. Average number of services per conception (NSC), conception rate (CR), and conception rate at first ser-vice (CRFS) was 1.8 (±1.4), 55, and 58%, respectively. The overall mean for the waiting period (WP), DFLS, and days open (DO) of cows was 109 (±52), 133 (±114), and 242 (±129) days, respectively. The mean for NSC, CR, and CRFS was 4.3 (±2.7), 23, and 14%, respectively. A very sig- nificant decrease in AFS and AC according to the year of birth, and a significant increase in AFS according to body weight at first insemination (>320 kg) were observed. The CRFS of heifers inseminated in 2013 was significantly higher than in 2014. Monthly mean CR in heifers and cows was negatively correlated with THI. The WP, DFLS, DO, and NSC of cows significantly decreased according to the year of calving. Cows that calved in rainy season had a significant-ly longer WP than in dry season. The occurrence of postpar-tum (PP) diseases was accompanied by an increase in WP, DO, and NSC. A decrease in body condition score (BCS) between calving and 60th day (C60) and also between 60th and 120th day of lactation resulted in a significant increase in WP and DO. A decrease in BCS between C60 was also ac-companied by a considerable reduction in CRFS of cows. Season and BCS at insemination had a significant effect on NSC and CR of cows. Reproductive performance was satis-factory for heifers, but poor for cows. Losses of BCS during the first months of lactation and at insemination were the major risk factors for this poor performance. Moreover, the season had a more negative effect on fertility in cows than in heifers. [less ▲]

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See detailSédimentologie et contrôle eustatique: cas du Miocène, Tunisie centre Nord
Belghithi, Hanen ULg

Doctoral thesis (2017)

En Afrique du Nord, au Néogène, la compression qui affecte le domaine atlasique témoigne de la convergence Afrique-Europe, et se marque par des dépôts de séries silicoclastiques du Miocène pauvres en ... [more ▼]

En Afrique du Nord, au Néogène, la compression qui affecte le domaine atlasique témoigne de la convergence Afrique-Europe, et se marque par des dépôts de séries silicoclastiques du Miocène pauvres en faune. Le présent projet s’intéresse à caractériser les variations spatiotemporelles des faciès, les variations eustatiques et les corrélations de ces séries miocènes. Pour ce faire, nous observons et analysons les différents mécanismes sédimentaires, afin d’identifier des surfaces remarquables corrélables et se baser sur l’analyse séquentielle et les variations de susceptibilité magnétique. Sur la base des données obtenues, l’objectif est de proposer un modèle sédimentologique, étudier les variations eustatiques à l’échelle régionale, établir des corrélations et élaborer un modèle paléogéographique des séries du Miocène en Tunisie. [less ▲]

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See detailStability-based validation of dietary patterns obtained by cluster analysis
Sauvageot, Nicolas ULg; Schritz, Anna; Alkerwi, Ala'a et al

in Nutrition Journal (2017), 16(3),

Abstract Background Cluster analysis is a data-driven method used to create clusters of individuals sharing similar dietary habits. However, this method requires specific choices from the user which have ... [more ▼]

Abstract Background Cluster analysis is a data-driven method used to create clusters of individuals sharing similar dietary habits. However, this method requires specific choices from the user which have an influence on the results. Therefore, there is a need of an objective methodology helping researchers in their decisions during cluster analysis. The objective of this study was to use such a methodology based on stability of clustering solutions to select the most appropriate clustering method and number of clusters for describing dietary patterns in the NESCAV study (Nutrition, Environment and Cardiovascular Health), a large population-based cross-sectional study in the Greater Region (N = 2298). Methods Clustering solutions were obtained with K-means, K-medians and Ward’s method and a number of clusters varying from 2 to 6. Their stability was assessed with three indices: adjusted Rand index, Cramer’s V and misclassification rate. Results The most stable solution was obtained with K-means method and a number of clusters equal to 3. The “Convenient” cluster characterized by the consumption of convenient foods was the most prevalent with 46% of the population having this dietary behaviour. In addition, a “Prudent” and a “Non-Prudent” patterns associated respectively with healthy and non-healthy dietary habits were adopted by 25% and 29% of the population. The “Convenient” and “Non-Prudent” clusters were associated with higher cardiovascular risk whereas the “Prudent” pattern was associated with a decreased cardiovascular risk. Associations with others factors showed that the choice of a specific dietary pattern is part of a wider lifestyle profile. Conclusion This study is of interest for both researchers and public health professionals. From a methodological standpoint, we showed that using stability of clustering solutions could help researchers in their choices. From a public health perspective, this study showed the need of targeted health promotion campaigns describing the benefits of healthy dietary patterns. [less ▲]

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See detailBreaking Bad News: the TAKE five program
VAN CAUWENBERGE, Isabelle ULg; GILLET, Aline ULg; Bragard, Isabelle ULg et al

Conference (2017, January 14)

Introduction For years, bad news delivery’s impact on patients or their relatives, as well as physicians’ stress has been a major concern. Based on studies claiming the efficacy of training courses to ... [more ▼]

Introduction For years, bad news delivery’s impact on patients or their relatives, as well as physicians’ stress has been a major concern. Based on studies claiming the efficacy of training courses to help physicians delivering such news, many protocols, like SPIKES, BREAKS or SHARE, have emerged worldwide. However, training to such protocol might be time-consuming and not suitable with junior doctors or trainees’ turnover. We hypothesised that a standardized 5-hours training program could improve bad news delivery practice. Participants and methods This preliminary study was conducted in the ED of a tertiary care academic hospital accounting for 90000 ED census per year, 16 attending physicians, 10 junior residents, and 5 trainees per month. Data were collected between November 2015 and April 2016. The study included 3 phases over 4 weeks. Video recorded single role-playing sessions happened the 1st (T1) and the 4th (T3) weeks. A 3-hour theory lesson happened the second week (T2), introducing the basics of therapeutic communication and delivering bad news. Each role-playing session lasted almost 1 hour (10 minutes briefing and medical case reading, 10 minutes role-plays and 40 minutes group debriefing). Bad news delivery performance was evaluated by a 14-points retrospective assessment tool (1). We collected data about the status and impact of a stressful event at 3-days using the French version of the IES-R scale (2). We applied Student t-tests for statistical analysis. Results 14 volunteers (10 trainees and 4 junior emergency physicians) were included in the study. On average, bad-news delivery process took 9’45’’ at T1 and 10’20’’ at T3. From T1 to T3, bad-news delivery performance increased significantly for both junior emergency physicians and trainees (p=0.0003 and p=0.0006, respectively). Further analysis revealed that most relevant increases involved the “situation” (p<0.001), “presentation” (p=0.009), “knowledge” (p=0.037), “emotions” (p=0.01) and “summary” (p=0.001) steps. We also found a significant decrease of the impact of bad-news delivery on trainee physicians’ stress (p=0.006). Discussion and conclusion These preliminary results indicate some potential for this new standardized course of bad news delivery. Apart from allowing physicians increase their communications skills, we believe that this simple 5-hour simulation-training program could alleviate physicians’ stress when they happen to break bad news. References 1. Brunet, A. et al. (2003). Validation of a French version of the Impact of Event Scale-Revised. Can J Psychiatry, 48(1), 56-61. 2. Park, I. et al. (2010). Breaking bad news education for emergency medicine residents: A novel training module using simulation with the SPIKES protocol. J Emerg Trauma Shock, 3(4), 385-388. [less ▲]

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