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See detailAvatars et actualité de la phénoménotechnique
Pieron, Julien ULiege

Conference (2017, April 24)

Detailed reference viewed: 27 (9 ULiège)
See detailDose-dependent effect of Estetrol on Angiogenesis and Tumor Growth
Gallez, Anne ULiege; Blacher, Silvia ULiege; Lenfant, Françoise et al

Poster (2017, April 24)

Hormone replacement therapies (HRT) based on estrogen preparations are the most powerful treatments to prevent menopause symptoms. However, they are associated to an increased risk of breast cancer and ... [more ▼]

Hormone replacement therapies (HRT) based on estrogen preparations are the most powerful treatments to prevent menopause symptoms. However, they are associated to an increased risk of breast cancer and they sustain the development of Estrogen Receptor α-positive tumors (ERα+). In addition, we have previously observed that estradiol (E2) can promote the growth of ERα-negative (ERα-) tumors, by increasing tumor angiogenesis that subsequently improves oxygen and nutrients delivery, thereby preventing hypoxia and necrosis. To identify new and safe drugs for the development of HRT presenting a better benefit/risk ratio, it is therefore necessary to evaluate the potential impact of new candidates on both ERα+ and ERα- tumors. In this context, estetrol (E4), a natural estrogen exclusively produced by the fetal liver, is a promising candidate. [less ▲]

Detailed reference viewed: 41 (6 ULiège)
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See detailCanopy aerodynamic distance (z-d) estimation and impact on eddy covariance measurements
Hurdebise, Quentin ULiege; De Ligne, Anne ULiege; Vincke, Caroline et al

in Geophysical Research Abstracts 2017 (2017, April 24)

Understanding if and how the spatial and temporal variability of the surrounding environment affects turbulence is essential for long-term eddy covariance measurements above growing and heterogeneous ... [more ▼]

Understanding if and how the spatial and temporal variability of the surrounding environment affects turbulence is essential for long-term eddy covariance measurements above growing and heterogeneous ecosystems. It requires characterizing the surrounding environment. One way to achieve this is to analyse the canopy aerodynamic distance, which is the difference between measurement height (z) and displacement height (d). In this study, twenty years of eddy covariance measurements from the Vielsalm Terrestrial Observatory, a site located in a mixed temperate forest, were used. Canopy aerodynamic distance (z-d) estimates were obtained using two micrometeorological methods: the first one, which is original so far as we know, was based on analysing sensible heat cospectra; the second one was derived from the wind speed profile equation. Canopy height estimates based on inventories were used to validate both methods. The micrometeorological methods allowed the z-d variations due to changes in canopy or measurement height to be detected. In addition, the results obtained using the two methods were well correlated, spatially and temporally, with the z-d derived from canopy height measurements. The micrometeorological approaches used could therefore be a promising tool for investigating z-d variability at a high directional and temporal resolution. Questions remain, however, particularly with regard to the variability observed that cannot be explained by canopy or measurement height variation. Forest management practices and the non-fulfilment of similarity relationships were suspected to be the main explanatory factors. [less ▲]

Detailed reference viewed: 36 (2 ULiège)
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See detailMomentum, sensible heat and CO2 correlation coefficient: what can we learn from 20 years of eddy covariance measurements
Hurdebise, Quentin ULiege; De Ligne, Anne ULiege; Vincke, Caroline et al

Poster (2017, April 24)

Long-term data series of carbon dioxide and other gas exchanges between terrestrial ecosystems and atmosphere become more and more numerous. Long-term analyses of such exchanges require a good ... [more ▼]

Long-term data series of carbon dioxide and other gas exchanges between terrestrial ecosystems and atmosphere become more and more numerous. Long-term analyses of such exchanges require a good understanding of measurement conditions during the investigated period. Independently of climate drivers, measurements may indeed be influenced by measurement conditions themselves subjected to long-term variability due to vegetation growth or set-up changes. The present research refers to the Vielsalm Terrestrial Observatory (VTO) an ICOS candidate site located in a mixed forest (beech, silver fir, Douglas fir, Norway spruce) in the Belgian Ardenne. Fluxes of momentum, carbon dioxide and sensible heat have been continuously measured there by eddy covariance for more than 20 years. During this period, changes in canopy height and measurement height occurred. The correlation coefficients (for momemtum, sensible heat and CO2) and the normalized standard deviations measured for the past 20 years at the Vielsalm Terrestrial Observatory (VTO) were analysed in order to define how the fluxes, independently of climate conditions, were affected by the surrounding environment evolution, including tree growth, forest thinning and tower height change. A relationship between canopy aerodynamic distance and the momentum correlation coefficient was found which is characteristic of the roughness sublayer, and suggests that momentum transport processes were affected by z-d. In contrast, no relationship was found for sensible heat and CO2 correlation coefficients, suggesting that the z-d variability observed did not affect their turbulent transport. There were strong differences in these coefficients, however, between two wind sectors, characterized by contrasted stands (height differences, homogeneity) and different hypotheses were raised to explain it. This study highlighted the importance of taking the surrounding environment variability into account in order to ensure the spatio-temporal consistency of datasets. [less ▲]

Detailed reference viewed: 24 (2 ULiège)
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See detailA terminology in General Practice / Family Medicine to represent non-clinical aspects for various usages
Jamoulle, Marc ULiege; Grosjean, Julien; Ittoo, Ashwin ULiege et al

in R. Randell et al. (Ed.) Informatics for Health: Connected Citizen-Led Wellness and Population Health (2017, April 24)

Abstract. The hereby proposed terminology called “Q-Codes” can be defined as an extension of the International Classification of Primary Care (ICPC-2). It deals with non-clinical concepts that are ... [more ▼]

Abstract. The hereby proposed terminology called “Q-Codes” can be defined as an extension of the International Classification of Primary Care (ICPC-2). It deals with non-clinical concepts that are relevant in General Practice/Family Medicine (GP/FM). This terminology is a good way to put an emphasis on underestimated topics such as Teaching, Patient issues or Ethics. It aims at indexing GP/FM documents such as congress abstracts and theses to get a more comprehensive view about the GP/FM domain. The 182 identified Q-Codes have been very precisely defined by a college of experts (physicians and terminologists) from twelve countries. The result is available on the Health Terminology/Ontology Portal (http://www.hetop.org/Q) and formatted in OWL-2 for further semantic considerations and will be used to index the 2016 WONCA World congress communications. [less ▲]

Detailed reference viewed: 105 (17 ULiège)
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See detailHow learning methods in anatomy allow a boost of visuospatial abilities for undergraduate students
Defaweux, Valérie ULiege; Ernst, Denise; Dernier, Adrienne ULiege et al

Poster (2017, April 24)

Because it is know that visuospatial abilities affect anatomy learning and that our students are heterogeneous related to these competences, it is essential to offer an educational strategy designed to ... [more ▼]

Because it is know that visuospatial abilities affect anatomy learning and that our students are heterogeneous related to these competences, it is essential to offer an educational strategy designed to specifically train and develop those skills at the beginning of the anatomy courses. We managed to offer various formative activities that improve visuospatial skills. [less ▲]

Detailed reference viewed: 35 (11 ULiège)
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See detailReduced Tillage generates higher N2O emissions: results of continuous chamber-based measurement in a winter wheat field.
Broux, François ULiege; Lognoul, Margaux ULiege; Theodorakopoulos, Nicolas et al

Poster (2017, April 24)

Agriculture is one of the most important contributors to GHG emission, notably through fertilized croplands. Though, few publications have studied simultaneously and through continuous measurement the N2O ... [more ▼]

Agriculture is one of the most important contributors to GHG emission, notably through fertilized croplands. Though, few publications have studied simultaneously and through continuous measurement the N2O and CO2 emissions in cultivated lands. We conducted this study to assess the effect of farming practices and climate on both N2O and CO2 emissions from a winter wheat crop. The experiment was held in an experimental field in the loamy region in Belgium from March 2016 till crop harvest in August 2016. The fluxes were measured on two nearby parcels in a winter wheat field with restitution of the residues from previous crop. For the past 8 years, one parcel was subjected to a Reduced tillage (RT, 10 cm depth) and the other one to a conventional tillage (CT, 25 cm depth). On each parcel, the emissions are assessed with homemade automated closed chambers. Measurement continuity and good temporal resolution (one mean flux every 4 hours) of the system allowed a fine detection and quantification of the emission peaks which usually represent the major part of N2O fluxes. In addition to gas fluxes, soil water content and temperature were measured continuously. Soil samples were taken regularly to determine soil pH, soil organic carbon and nitrogen pools (total, NO3- and NH4+) and study microbial diversity and nitrification/denitrification gene expression. Surprisingly, results showed N2O emissions twice as large in the RT parcel as in the CT parcel. On the contrary, less important CO2 emissions were observed under RT. Several emission peaks of N2O were observed during the measurement period. The peaks occurred after fertilization events and seemed to be triggered by an elevation of soil water content. Interesting links could be made between soil NH4-N and NO3-N pools and N2O emissions. Nitrification being the main process originating the fluxes was suggested on the one hand by the temporal evolution of nitrogen pools and N2O emissions and on the other hand by the relation between spatial variability of the emissions with the soil nitrate content. A comparison of the emissions between ST and CT and a discussion on peaks temporal dynamic, focusing on their intensity, duration and starting time will be presented. [less ▲]

Detailed reference viewed: 53 (6 ULiège)
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See detailSalinity impact on seed yield, polyphenols composition and antioxidant activity of Fennel (Foeniculum vulgarae Mill) extracts
Bettaieb Rebey, Ines; Bourgou, S.; Msaada, K. et al

Poster (2017, April 24)

Detailed reference viewed: 15 (1 ULiège)
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See detailGeomorphic and Hydrological challenges in Africa: implications for soil and water conservation
Vanmaercke, Matthias ULiege; Poesen, Jean

Conference (2017, April 24)

Expected scenarios of climate change and population growth confront Africa with various important challenges related to food, water and energy security. Many of these challenges are closely linked to the ... [more ▼]

Expected scenarios of climate change and population growth confront Africa with various important challenges related to food, water and energy security. Many of these challenges are closely linked to the impacts of soil erosion and other geomorphic processes, such as reduced crop yields, sedimentation of reservoirs and reduced freshwater quality. Despite the urgency and extent of many of these challenges, the causes and dynamics of these processes and their impacts remain severely understudied. This becomes apparent when the availability of e.g. soil erosion and catchment sediment export measurements for Africa is compared to that of other continents. Nonetheless, a substantial amount of geomorphic research has been conducted in Africa. Many of this work dates back from several decades ago, and were often only reported in ‘gray literature’ (e.g. internal reports). Here we present an overview of our current state of knowledge on soil erosion and its implications in Africa. We discuss which geomorphic process rate measurements are currently available and what can be learned from these with respect to the challenged raised above. We especially focus on our current understanding about the effectiveness of soil and water conservation techniques at various spatial and temporal scales. Based on specific case-studies (e.g. in Ethiopia and Uganda) and a meta-analysis of previous work, we highlight some research gaps, research needs and research opportunities when aiming to use Africa’s soil and water resources sustainably and efficiently [less ▲]

Detailed reference viewed: 17 (1 ULiège)
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See detailDetermining RUSLE P-factors for stonebunds and trenches in rangeland and cropland, Northern Ethiopia
Taye, Gebeyehu; Poesen, Jean; Vanmaercke, Matthias ULiege et al

Conference (2017, April 24)

The implementation of soil and water conservation (SWC) measures in the Ethiopian highlands is a top priority to reduce soil erosion rates and to enhance the sustainability of agroecosystem. Nonetheless ... [more ▼]

The implementation of soil and water conservation (SWC) measures in the Ethiopian highlands is a top priority to reduce soil erosion rates and to enhance the sustainability of agroecosystem. Nonetheless, the effectiveness of many of these measures for different hillslope and land use conditions remains currently poorly understood. As a result, the overall effects of these measures at regional or catchment scale remain hard to quantify. This study addresses this knowledge gap by determining the cover-management (C) and support practice (P) factors of the Revised Universal Soil Loss Equation (RUSLE), for commonly used SWC measures in semi-arid environments (i.e. stone bunds, trenches and a combination of both). Calculations were based on soil loss data collected with runoff plots in Tigray, northern Ethiopia (i.e. 21 runoff plots of 600 to 1000 m2 , monitored during 2010, 2011 and 2012). The runoff plots were installed in rangeland and cropland sites corresponding to a gentle (5%), medium (12%) and steep (16%) slope gradients. The C and P factors of the RUSLE were calculated following the recommended standard procedures. Results show that the C-factor for rangeland ranges from 0.31 to 0.98 and from 0.06 to 0.39 for cropland. For rangeland, this large variability is due to variations in vegetation cover caused by grazing. In cropland, C-factors vary with tillage practices and crop types. The calculated P-factors ranged from 0.32 to 0.74 for stone bunds, from 0.07 to 0.65 for trenches and from 0.03 to 0.22 for a combination of both stone bunds and trenches. This variability is partly due to variations in the density of the implemented measures in relation to land use (cropland vs rangeland) and slope angles. However, also annual variations in P factor values are highly significant. Especially trenches showed a very significant decline of effectiveness over time, which is attributable to their reduced static storage capacity as a result of sediment deposition (e.g. for trenches in rangeland: 0.07-0.13 in 2010 to 0.37-0.65 in 2012). Hence, the results of this work may not only help in better modelling and quantifying the average long-term impacts of SWC measures over larger areas, but also show the importance of considering temporal variations of the effectiveness of SWC measures. [less ▲]

Detailed reference viewed: 38 (1 ULiège)
See detailCancer associated fibroblast-derived integrin α11 regulates PDGFRβ signaling to promote breast cancer progression
Primac, Irina ULiege; Blacher, Silvia ULiege; cimino, Jonathan et al

Conference (2017, April 24)

CAF-specific proteins can provide important prognostic markers and targets for anticancer drugs. Recently, integrin α11 (ITGA11) emerged as a new biomarker of CAFs. ITGA11 is mainly expressed by ... [more ▼]

CAF-specific proteins can provide important prognostic markers and targets for anticancer drugs. Recently, integrin α11 (ITGA11) emerged as a new biomarker of CAFs. ITGA11 is mainly expressed by mesenchymal cells and is correlated with fibroblast activation and matrix reorganization. While the role of ITGA11 in wound healing has been well described, only a very limited number of reports have assessed its role in the cancer disease. This research project aims to investigate the role of stromal ITGA11 in breast cancer. To analyze the in vivo effects of ITGA11 on tumor insurgence, growth and metastasis, we crossed the oncogenic MMTv-PyMT mice with the ITGA11 KO/WT mice, which develop spontaneously breast tumors. ITGA11 deletion strongly delayed tumor growth and metastasis in PyMT mouse model. ITGA11 was poorly expressed at early stages of the tumor progression and its expression was strongly increased in the late stage invasive carcinomas. Importantly, a reduced angiogenesis and collagen content was observed in tumors lacking of ITGA11. Furthermore, a strong co-localization between ITGA11 and PDGFRb, but not other CAF markers such as alpha smooth actin, was also observed within the tumor stroma, suggesting that ITGA11 defines a subpopulation of CAFs, which is not represented by myofibroblasts, but rather PDGFRb+ CAFs. For mechanistic investigation, CAFs and breast cancer cells were isolated from the PyMT model. ITGA11 co-immunoprecipitated with PDGFRb in the isolated CAFs and regulated its phosphorylation. Interestingly, ITGA11-deficient CAFs failed to promote CAF and cancer cell invasion, in contrast to WT CAFs in a spheroid invasion assay. A high throughput comparative proteomics analysis on CAF spheroids in 3D a system was next performed. Proteomics data identified several proteins with relevance in the cancer disease which were significantly modulated in CAFs through ITGA11 down-regulation. The top-ranking candidates are under validation and molecular pathways, which may link these targets and ITGA11 will be further analyzed in the in vitro models. Overall, these in vivo and in vitro data show that ITGA11 defines a PDGFRβ+ subpopulation of CAFs distinct from α-SMA+ myofibroblasts that promote tumor cell invasion and angiogenesis at late stages of carcinoma evolution. ITGA11 is a promising target within the stroma of breast cancer and further investigations of its molecular signaling pathways will be of great relevance. [less ▲]

Detailed reference viewed: 63 (9 ULiège)
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See detailTransfert sol-plante et Procédés de phytoremédiation (Memoris)
Liénard, Amandine ULiege

Conference given outside the academic context (2017)

Detailed reference viewed: 40 (2 ULiège)
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See detailCharacterizing root system characteristics with Electrical resistivity Tomography: a virtual rhizotron simulation
Rao, Sathyanarayan; Ehosioke, Solomon ULiege; Lesparre, Nolwenn et al

Conference (2017, April 24)

Electrical Resistivity Tomography (ERT) is more and more used for monitoring soil water content in a cropped soil. Yet, the impact of roots on the signal is often neglected and a topic of controversy. In ... [more ▼]

Electrical Resistivity Tomography (ERT) is more and more used for monitoring soil water content in a cropped soil. Yet, the impact of roots on the signal is often neglected and a topic of controversy. In several studies related to soil-root system, it has been showed that the measured root mass density statistically correlates with the electrical conductivity (EC) data obtained from ERT. In addition, some studies suggest that some roots are more electrically conductive than soil for most water content. Thus, higher EC of roots suggest that it might have a measurable impact on ERT signals. In this work, virtual rhizotrons are simulated using the software package called R-SWMS that solves water and solute transport in plant root-soil system, including root growth. The distribution of water content obtained from R-SWMS simulation is converted into EC data using pedo-physical models. The electrical properties of roots and rhizosphere are explicitly included in the EC data to form a conductivity map (CM) with a very detailed spatial resolution. Forward ERT simulations is then carried out for CM generated for various root architectures and soil conditions to study the impact of roots on ERT forward (current and voltage patterns) and inverse solutions. It is demonstrated that under typical injection schemes with lateral electrodes, root system is hardly measurable. However, it is showed that adding electrodes and constraints on the ERT inversion based on root architecture help quantifying root system mass and extent. [less ▲]

Detailed reference viewed: 21 (1 ULiège)
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See detailThe growth and meat quality of H'mong chicken raised by industrial farming
Nguyen Van Duy, ULiege; Vu Dinh, Ton; Nguyen Thi, Phuong

in Journal of Sciences of Agriculture Vietnams (2017), 15(4), 438-445

This study was carried out at the experimental farm of Vietnam National University of Agriculture from January to December, 2016 on H’mong chickens that were raised by industrial farming. H’mong chickens ... [more ▼]

This study was carried out at the experimental farm of Vietnam National University of Agriculture from January to December, 2016 on H’mong chickens that were raised by industrial farming. H’mong chickens were raised in three lots in order to observe the survival rate, growth capacity, FCR and quality of meat. The results show that Hmong chicken adapted well with industrial farming method, which supposedly contributed to the improvement in survival rate of chickens (94,1%) compared to traditional free-range farming method.. H'mong chickens have low weight and considerable growth speed. Average daily gain of H’mong chickens was increasing gradually from one to ten weeks of age and then decreasing. From one to 12 weeks, H'mong chickens consumes averagely 24.81 grams of feed per day and Feed Conversation Rate was 3.1 kg of feed/kg live body weight. Twelve week-old roosters and hens achieved body weight at 1206,7g and 1026,7g in respectively. H'mong chicken is a dual-purpose breed, producing an amount of thigh meat 1.3 times greater than breast meat. The proportion of iron in Hmong chicken meat is higher than that in other domestic chicken breeds and there are eight unsubstituted amino acids in the meat. Key works: H’mong chickens, industrial farming. [less ▲]

Detailed reference viewed: 68 (2 ULiège)
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See detailCattle grazing dynamics under contrasted pasture characteristics at temporal and spatial scales
Andriamandroso, Andriamasinoro ULiege

Doctoral thesis (2017)

Grassland constitutes an important and a low-cost food source for grazing livestock. Optimal management should consider both forage resource productivity and animal needs. For cattle, grazing is a normal ... [more ▼]

Grassland constitutes an important and a low-cost food source for grazing livestock. Optimal management should consider both forage resource productivity and animal needs. For cattle, grazing is a normal behavior displayed in an attempt to eat the amount of forage to fulfill their nutritive requirements for maintenance and production. It is the most time-consumed activity of cows reared in pasture-based systems. With the increase of herd size, on one hand, farmers have been constrained to integrate innovative tools and techniques, such as milking robot, to improve the production system in particular to reduce the labor cost. On the other hand, such change might reduce time allocated for grazing on pasture. However pasture-based systems constitute a real pillar for sustainability as they are socially acceptable and environmentally profitable as they play an important role on ecosystem services and biodiversity provision. Studying grazing processes at individual level, which finally is the key point of animal-plant interactions, is a valuable research domain to enhance the knowledge about this mechanism and to feed decision support tools. This thesis aimed to link the changes in pasture characteristics to the grazing behavior of cattle in order to better understand the grazing strategy under different pasture characteristics and forage allowances. To allow an individual monitoring, sensor technology has integrated within farms and livestock researches to monitor many physical variables, inducing the emergence of precision livestock farming approach. Different types of sensors were designed, and already commercialized for some, primarily for physiological status detections such as heat, parturition or diseases. Grazing behaviors could be monitored using pressure, electromyography, acoustic or accelerometric sensors by classifying posture and movements of the animal into unitary behaviors (grazing, ruminating, resting, walking, etc.) and finer behavior such as chews and bites through jaw movements’ detection. When compared to real observation, detection accuracies of these behaviors were variable according to the type of sensor, its position on the animal during data acquisition on pasture, the data recording frequency, the time-window and the method dedicated to the post-recording data analysis. State-of-the-art analysis demonstrated a great performance of accelerometers for unitary behaviors and bites detection. An inertial measurement unit, integrating accelerometer, gyroscope and location sensors, was used for recording cattle movements during grazing at high sampling rate (100Hz). It allows a correct detection of grass intake and rumination behaviors with an average accuracy of 91% using 1-second time-window when calibrating and validating the detection algorithm. Deeper analysis of accelerometric signal allowed us to detect bites and chews performed during grazing and ruminating. Effects of pasture heights on grazing bites characteristics were differentiated by a higher frequency when pasture is at a lower height. Finally when combined to geographical information, a similar pattern was observed for cattle grazing on the same spot confirming their herd movement during grazing in terms of bites location. Differences were visible under different pasture heights but not significant. Such bites location, combined with continuous monitoring of cattle behaviors, through use of sensors, should be furtherly linked with more pasture characteristics, if possible with the same accuracy, and monitored on longer period in order to obtain a complete coverage of cattle grazing strategy and the effect of contrasted environment in order to purpose valuable tool for a better grazing management. [less ▲]

Detailed reference viewed: 102 (18 ULiège)
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See detailTo be plastic is fantastic: delineate coral species niches for assessing their tolerance to changes
Denis, Vianney; Sturaro, Nicolas ULiege; Yang, Shan-Hua et al

Conference (2017, April 24)

Climatic and anthropogenic disturbances alter coral reefs by reconfiguring existing coral assemblages. Surviving species are selected by the new environment based on particular traits that they may ... [more ▼]

Climatic and anthropogenic disturbances alter coral reefs by reconfiguring existing coral assemblages. Surviving species are selected by the new environment based on particular traits that they may exhibit. The plasticity in traits will define ecological strategies associated with contrasted degrees of tolerance to changes. In this process, specialists are expected to tolerate few changes to the environmental conditions and are restricted to specific habitat. To contrast, generalists can cope with a wider range of environmental conditions by readjusting traits according to the habitat’s features. Ecological strategies in corals have been exclusively defined according to species’ trait averages, irrespective of individual variations. Challenges representing the acquisition and use of energy have also tended to be oversimplified, specifically by the choice of easy traits in the absence of strong scientific evidence. Here, we propose a framework to re-examine strategies in scleractinian corals by focusing on the intraspecific variation of traits. We will show how the characteristics of a given species niche can help coral species to tolerate changes, illustrating this approach with examples taken from high-latitude locations and mesophotic coral ecosystems. We will demonstrate that multidisciplinary approach focusing on three major characteristics of the coral holobiont (its physiology, trophic ecology, and associated micriobiome), we can enhance the comprehension of ecological plasticity of coral species and predict future ecosystem reconfiguration. [less ▲]

Detailed reference viewed: 33 (1 ULiège)
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See detailComment on “Hypogonadotrophic hypogonadism due to a mutation in the luteinizing hormone β-subunit gene”
VALDES SOCIN, Hernan Gonzalo ULiege; Daly, Adrian ULiege; BECKERS, Albert ULiege

in Korean Journal of Internal Medicine (The) (2017), 32(3), 566-567

Detailed reference viewed: 17 (4 ULiège)
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See detailClay minerals behaviour in thin sandy clay-rich lacustrine turbidites (Lake Hazar, Turkey)
El Ouahabi, Meriam ULiege; Hubert, Aurelia ULiege; Lamair, Laura ULiege et al

Poster (2017, April 23)

Turbidites have been extensively studied in many different areas using cores or outcrop, which represent only an integrated snapshot of a dynamic evolving flow. Laboratory experiments provide the missing ... [more ▼]

Turbidites have been extensively studied in many different areas using cores or outcrop, which represent only an integrated snapshot of a dynamic evolving flow. Laboratory experiments provide the missing relationships between the flow characteristics and their deposits. In particular, flume experiments emphasize that the presence of clay plays a key role in turbidity current dynamics. Clay fraction, in small amount, provides cohesive strength to sediment mixtures and can damp turbulence. However, the degree of flocculation is dependent on factors such as the amount and size of clay particles, the surface of clay particles, chemistry and pH conditions in which the clay particles are dispersed. The present study focuses on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in stacked thin beds. Depositional processes and sources have been previously studied and three types were deciphered, including laminar flows dominated by cohesion, transitional, and turbulence flow regimes (Hage et al., in revision). For the purpose of determine the clay behavior in the three flow regimes, clay mineralogical, geochemical measurements on the cores allow characterising the turbidites. SEM observations provide further information regarding the morphology of clay minerals and other clasts. The study is particularly relevant given the highly alkaline and saline water of the Hazar Lake. Clay minerals in Hazar Lake sediments include kaolinite (1:1-type), illite and chlorite (2:1-type). Hazar lake water is alkaline having pH around 9.3, in such alkaline environment, a cation-exchange reaction takes place. Furthermore, in saline water (16‰), salts can act as a shield and decrease the repulsive forces between clay particle surfaces. So, pH and salt content jointly impact the behaviour of clays differently. Since the Al-faces of clay structures have a negative charge in basic solutions. At high pH, all kaolinite surfaces become negative-charged, and then kaolinite particles are dispersed, and the suspension is stabilized supported by our SEM observations. In alkaline water, kaolinite reveals a lower degree of consolidation. While, alkaline water has no measurable effect on illite and chlorite surface properties due to the absence of modifications in charge. Illite and chlorite form with other clasts clusters or aggregate structures in suspension when the particle interactions are dominated by attractive energies were formed. The aggregate structure plays a major part in the flow behavior of clay suspensions. Flocs will immobilize the suspending medium, and give rise to increasing viscosity and yield strength of the suspension. [less ▲]

Detailed reference viewed: 21 (2 ULiège)