Last 7 days
Bookmark and Share    
Full Text
See detailSous-arbres induits pleinement feuillus
Vandomme, Elise ULg

Scientific conference (2017, January 19)

In the last 60 years, polyominoes have been the object of many investigations. A central problem, that is still open, is to determine the number of polyominoes with n square cells. An approach to solve ... [more ▼]

In the last 60 years, polyominoes have been the object of many investigations. A central problem, that is still open, is to determine the number of polyominoes with n square cells. An approach to solve the problem is to use a combinatorial description of polyominoes and to try to describe particular families of polyominoes. Behind each polyomino there is a graph whose vertices are the cells, such that two vertices are adjacent if their cells share a common edge. In this framework, one can study the polyominoes with an acyclic graph, called tree-like polyominoes. In 2016, Blondin-Massé et al. determined the maximal number that can have a tree-like polyomino with n cells. In this talk, we generalize this problem to graphs in general and we show this problem is NP-complete. However, the problem becomes polynomial when we restrict ourselves to trees or to graphs with a constant tree-width. [less ▲]

Detailed reference viewed: 15 (1 ULg)
Full Text
Peer Reviewed
See detailGenetics of Pituitary Tumor Syndromes
Daly, Adrian ULg; BECKERS, Albert ULg

in Melmed, Shlomo (Ed.) The Pituitary (2017)

Detailed reference viewed: 27 (5 ULg)
See detailMoresnet-Neutre (1816-1919): Histoire et mémoire d'une curiosité géopolitique
Brüll, Christoph ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailIntegrated approach for ethics in research for young researchers at the University of Liege
Halleux, Isabelle ULg

E-print/Working paper (2017)

For ensuring good practices in research from the beginning and developing a culture of ethics, ULg developed an integrated approach focusing on young researchers. The objective is to instill, as soon as ... [more ▼]

For ensuring good practices in research from the beginning and developing a culture of ethics, ULg developed an integrated approach focusing on young researchers. The objective is to instill, as soon as possible, a good perception of what is quality in research, considering methodology, project management and ethics as norms and moral positioning for solving dilemma. Actions, coordinated by the Council for Ethics and Scientific Integrity (CEIS), are developed simultaneously through 5 axes. Young researchers are involved at all levels of the process, directly or as representative of the PhD Association. 1. Training: Sensitization and education to ethics; development of professional capacities, incl. data analysis & open data; seminaries with supervisors and PhDs ("duos") 2. Forum: ethics on the public space – Seminaries, conference, round tables, intervision, discussion and exchange on questions, dilemma, case-studies, with the help of external experts 3. Research appraisal: requirement for an ethics appraisal of each research project, with a special focus on human and social sciences, with the help of disciplinary ethics committees 4. Ethics analysis: Analysis of special questions, complains, problems, and decision making in case of violation of integrity 5. Regulation: Writing of procedures, dissemination of documents, recommendations and case-studies, link to the HR Strategy for researchers and the Charter and Code. In 2016, successful activities took place : - about 500 PhDs (25%) participated directly in the "Go2thesis training" (incl. 1 day on project management and ethics), dedicated trainings (introduction, special questions) and forum-debates - all the research projects, incl. PhD grants, supported by ULg were requested to provide an ethical issue check list, based on the H2020 standards. The R&D Office helped to explain about the issues and resources, and to orient the applicant to the ad hoc ethics committee - special requests were analyzed by the CEIS for several PhD's sensitive projects - Information was provided to PhDs regarding authorship, crowdfunding, privacy, open data and security while travelling New projects will be developed for (1) strengthening the relation between CEIS-ethics committee-doctoral school-supervisor-PhD (2) involving all the new PhDs in the training and forum, and (3) ensure the ethics appraisal during the whole duration of the PhD thesis (i.e. special chapter in the annual report). This presentation aims to exchange about what was done, the actual and expected impact of actions, what is going right and wrong, and how ULg is managing this dynamics as part of the HR Strategy for researchers project. A discussion with participants is expected on results and new projects. [less ▲]

Detailed reference viewed: 38 (4 ULg)
See detailA persistent meteoric layer in Mars' atmosphere
Crismani; Schneider; Plane et al

Poster (2017, January 18)

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 40 (8 ULg)
Full Text
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 ▲]

Detailed reference viewed: 71 (4 ULg)
See detailGlobal UV Imaging by MAVEN/IUVS: Diurnal Cloud Formation, Dust Storms and Atmospheric Scattering.
Schneider; Deighan; Jain et al

Conference (2017, January 17)

Detailed reference viewed: 13 (1 ULg)
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)

Detailed reference viewed: 30 (4 ULg)
Full Text
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 ▲]

Detailed reference viewed: 20 (3 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 10 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 27 (3 ULg)
Full Text
See detailLes institutions politiques belges
Grandjean, Geoffrey ULg

Learning material (2017)

Detailed reference viewed: 32 (1 ULg)
Full Text
See detailLeidenfrost effect at its limits
Maquet, Laurent ULg

Doctoral thesis (2017)

Detailed reference viewed: 66 (10 ULg)
See detailNO Nightglow studies status
Stiepen, Arnaud ULg; Jain; Deighan et al

Conference (2017, January 16)

Detailed reference viewed: 9 (1 ULg)
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)
Full Text
See detailPrésentation de cas cliniques
WANG, François-Charles ULg

Scientific conference (2017, January 16)

Detailed reference viewed: 16 (0 ULg)
Full Text
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 ▲]

Detailed reference viewed: 28 (5 ULg)