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See detailThermal history modelling to understand microstructures observed in repair technology of Ti-6Al-4V
Tomé Jardin, Ruben Antonio ULiege; Tchuindjang, Jérôme Tchoufack ULiege; Paydas, Hakan ULiege et al

Conference (2017, June 28)

Study of laser cladding as a possible technology to repair Ti-6Al-4V. Development of a FEM thermal to predict microstructure.

Detailed reference viewed: 26 (6 ULiège)
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See detailAn integrated logistics decision support model for city logistics
Limbourg, Sabine ULiege

Scientific conference (2017, June 28)

Today, more than 50% of the world's population lives in cities; the urban population is projected to reach 85% by 2100. Mainly due to urbanization and e-commerce, the demand for urban freight transport ... [more ▼]

Today, more than 50% of the world's population lives in cities; the urban population is projected to reach 85% by 2100. Mainly due to urbanization and e-commerce, the demand for urban freight transport (both forward flows and reverse flows) is clearly growing. But, transport is also responsible for a large share of urban air pollution as well as noise nuisance. Thus, an integrated logistics system to optimize transport network and service design, as well as vehicles routing of a variety of modes has to be developed. The objective is to determine how to efficiently move freight by means of these services and vehicles, while reducing negative environmental impacts. The topic includes research questions related to the demand to be serviced, the type and number of facilities needed to store and consolidate freight, the better utilization of vehicle capacity (fill rate and fewer empty trips: on average, 25% of goods vehicles in Europe run empty) and the reduction of energy consumption. [less ▲]

Detailed reference viewed: 35 (1 ULiège)
See detailFrom internal experts to external interlocutors? EU agencies and procedures assessing the equivalence of third country legal rules with EU regulatory standards
Van Cleynenbreugel, Pieter ULiege

Scientific conference (2017, June 28)

this paper will offer an overview of procedures allowing EU agencies to determine the equivalence of third country regulatory regimes and conceptualise the accountability challenges they pose. Proceeding ... [more ▼]

this paper will offer an overview of procedures allowing EU agencies to determine the equivalence of third country regulatory regimes and conceptualise the accountability challenges they pose. Proceeding in three parts, the first part will identify and classify the different third country equivalence procedures in place. Analysing the legal basis for agency intervention and the specific powers granted to the respective agencies in that respect, this part will allow to develop a topology of two different equivalence roles conferred on EU agencies. Building upon this descriptive analysis, the second part will identify two accountability challenges associated with each of the identified third country equivalence procedure categories. Seeking to overcome those challenges, the third part of the paper will make four pointed suggestions aimed at recognising explicitly and in a more centralised way the external action powers conferred on EU agencies. Doing so would at the very least allow better to tailor modifications to the external action frameworks against the background of which existing equivalence procedures currently already implicitly operate. [less ▲]

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Peer Reviewed
See detailDecreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet
Hofer, S.; Tedstone, A.; Fettweis, Xavier ULiege et al

in Science (2017), 3(6),

The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the ... [more ▼]

The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation. [less ▲]

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See detailOn the transition between symmetric and asymmetric flow in rectangular shallow reservoirs - a case of maximum energy dissipation?
Westhoff, Martijn; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

Conference (2017, June 28)

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with ... [more ▼]

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with identical recirculation zones on both sides. In longer reservoirs, the main jet reattaches to the side of the reservoir leading to small and large recirculation zones. Previous studies have found an empirical geometric relation describing the switch between these two flow patterns. In this study, we demonstrate, with a simple analytical model, that this switch coincides with a maximization of energy dissipation in the shear layer between the main jet and recirculation zones: Short reservoirs dissipate more energy when the flow pattern is symmetric, while longer reservoirs dissipate more energy with an asymmetric pattern. This approach enables the prediction of the flow patterns without detailed knowledge of small scale processes, potentially useful in the early phase of reservoir design. [less ▲]

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See detailHolomorphic cohomological convolution
Dubussy, Christophe ULiege

Poster (2017, June 28)

In his thesis, T. Pohlen succeeded in defining a Hadamard product between holomorphic functions defined on star-eligible subsets of the Riemann sphere. We show how this theory is actually a particular ... [more ▼]

In his thesis, T. Pohlen succeeded in defining a Hadamard product between holomorphic functions defined on star-eligible subsets of the Riemann sphere. We show how this theory is actually a particular case of the holomorphic cohomological convolution, defined in a general way thanks to the integration map on complex Lie groups. [less ▲]

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See detailWear behaviour of laser clad High Speed Steels thick deposits
Hashemi, Seyedeh Neda ULiege; Tchuindjang, Jérôme Tchoufack ULiege; Dedry, Olivier ULiege et al

Conference (2017, June 28)

The wear behaviour of 4 different High Speed Steel (HSS) thick coatings (one cast material and 3 laser clad deposits with varying Mo, V and W contents) was investigated at 2 different test temperatures, i ... [more ▼]

The wear behaviour of 4 different High Speed Steel (HSS) thick coatings (one cast material and 3 laser clad deposits with varying Mo, V and W contents) was investigated at 2 different test temperatures, i.e. at room temperature and at 300°C. For all four materials under both test conditions, oxidative wear was identified as the main wear mechanism. The 3 laser clad deposits exhibit a higher wear resistance compared to the conventional cast reference material, and this effect was mainly attributed to their strongly refined microstructures. Moreover, a detailed comparison of the wear behaviour of the 3 laser clad deposits, in correlation with their microstructures, allows a better understanding of the effect of the different carbides and of their morphology. [less ▲]

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See detailFrom local initiatives to territorial transition project: case study of a grassroots food belt project in Liège (Belgium)
Feyereisen, Marlène ULiege; Stassart, Pierre M ULiege; Jonet, Christian

Conference (2017, June 28)

This study analyses a local food initiatives in Liege (Belgium) linked to the Transition Network movement: Ceinture Aliment-Terre Liégeoise (CATL). The study aims to analyse how CATL evolved from a ... [more ▼]

This study analyses a local food initiatives in Liege (Belgium) linked to the Transition Network movement: Ceinture Aliment-Terre Liégeoise (CATL). The study aims to analyse how CATL evolved from a marginal grassroots movement, to a project of transition of the agri-food system which is considered exemplary by Belgian institutional actors. [less ▲]

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See detailAntimicrobial activities of key intermediate plant oxylipins
Deboever, Estelle ULiege

Conference (2017, June 28)

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated ... [more ▼]

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated fatty acids (PUFAs), appear to be crucial agents in plant defense mechanisms. Among plant oxylipins, the 13-hydroperoxy oxylipins (13-HPO) constitute key intermediate oxylipins (KIOs) as they can be converted into jasmonic acid, OPDA, dn-OPDA or traumatic acid, well-characterized components involved in plant resistance mechanisms. Their presumed functions include direct antimicrobial effect, stimulation of plant defense gene expression, and/or regulation of plant cell death. However, the precise contribution of each KIOs to plant defense remains essentially unknown. In this work, we focus on two h13-HPO, the 13(S)-hydroperoxy-octadecadienoic acid (13-HPOD) and the 13(S)-hydroperoxy-octadecatrienoic acid (13-HPOT). In vitro growth inhibition assays were performed to investigate the direct antimicrobial activities against 7 pathogens of agronomic interest including bacteria, oomycetes and fungi. This study showed unambiguously that 13-HPO are able to hinder growth of some plant microbial pathogens, generally with a higher efficacity for 13-HPOT. In order to get a better insight into their mechanism of action, a complementary in silico and experimental biophysical approach was applied. Biomimetic pathogen plasma membranes are used to study the mechanism at the molecular level. Slight conformational differences may have significant impacts on their ability to interact with pathogens lipids and plasma membranes. [less ▲]

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See detailAbsent, yet present? Tracing "Responsible Research and Innovation" in Radiation Protection Research
Van Oudheusden, Michiel ULiege

Conference (2017, June 28)

In this paper, I argue that although the notion of responsible research and innovation (RRI) is manifestly absent in research programs for radiation protection and nuclear research and training, RRI is ... [more ▼]

In this paper, I argue that although the notion of responsible research and innovation (RRI) is manifestly absent in research programs for radiation protection and nuclear research and training, RRI is increasingly recognized, and mobilized, by various actors in the field; is an essentially contested concept; and facilitates the development of a sizeable network comprising actors with a variety of roles, expectations and stakes, including researchers in the social sciences and humanities (SSH). To sustain these points, I draw on my experiences as an embedded social scientist in nuclear research, singling out sites and instances (e.g. the crafting and dissemination of the 2015 Ricomet Public Declaration, SSH research within the EU-Concert framework, conversations with radiation protection researchers) where RRI is explicitly discussed, propagated, negated, or transformed. This exploration highlights recurring challenges of “translating” RRI to radiation protection research, such as the strong evaluative connotation of RRI and its top-down character; the lack of industry involvement in RRI processes; the tight connection between RRI and new and emerging technologies; and the hybridization of SSH through inter- and transdisciplinary research. I discuss each of these challenges in turn, with the aims of reflexively considering how RRI is co-produced in radiation protection research through negotiations between stakeholders and the interplay of practices and artifacts; and what the potential implications of these processes are for SSH engagement in the field. [less ▲]

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See detailThe behavior of pesticide during beer brewing and the toxicity of pesticide using state-of-the-art omic tools
Kong, Zhiqiang ULiege

Doctoral thesis (2017)

Beer is an extremely popular beverage worldwide, representing the third-most popular drink after water and tea. And barley is the major raw material used for beer production. However, various combinations ... [more ▼]

Beer is an extremely popular beverage worldwide, representing the third-most popular drink after water and tea. And barley is the major raw material used for beer production. However, various combinations of pesticides are widely used at several stages of barley culti¬vation and during post-harvest storage to control pest and fungal disease. Hence, traces of these pesticides might remain in the beer produced from the treated ingredients. Hence, monitoring trace levels of pesticide residues during beer brewing and investigated the effects of pesticide residue on the quality of beer is essential. First, the behavior and fate of 3 pesticides (triadimefon, malathion, and dichlorvos) and the main metabolites (triadimenol and malaoxon) during barley storage or beer processing were assessed using a pilot-plant equipment. The residues of all products were determined using liquid chromatography coupled with tandem mass spectrometry. Field investigation of the dissipation rate kinetics for triadimefon and malathion during storage indicated that their half-life was twice as high when 5 times the recommended dosage was used. Milling had little effect on removing dichlorvos and malathion residues, whereas they were substantially removed when the spent grains were mashed. The calculated processing factors after processing were all <1, indicating that the residual ratios of dichlorvos and malathion were reduced during the entire process. In conclusion, storage and processing extensively reduced pesticide residue levels in barley and beer; however, greater focus needs to be paid to the toxicity of their metabolites in commercial by-products. Then we selected the triadimefon as the target fungicide to further study its behavior, the dissipation kinetics of TF during fermentation mediated by two different yeast strains, Saccharomyces cerevisiae IAPPST 1401 (Y1) and CICC 1202 (Y2), and found that Y2 promoted the degradation of TF. Response surface methodology was used to optimize fermentation process variables, in order to achieve the maximum removal rate of TF and the minimum production of its corresponding metabolite, triadimenol (TN). Triadimefon is also a widely used triazole fungicide with one chiral carbon center, Stereoselective degradation of triadimefon was found during barley storage, the half-life of S-(+)-triadimefon was 36.5d, 31.5d and 30.1d, while R-(-)-traidmefon was 69.3d, 53.3d and 33d under 4°C, 25°C and 40°C, respectively. During brewing process, both enantiomers of triadimefon were easily degraded. After fermentation, little triadimefon detected in the beer, while RS-(+) and SS-(-)-triadimenol were detectable. This research provides accurate information for evaluating the risk of food safety. Furthermore, we investigated the effect of triadimefon affect the quality and flavor of the fermented beer, The effect of triadimefon on yeast growth and the sensory quality of beer were studied. There were significant differences in sensory quality between beer samples fermented with and without triadimefon based on data obtained with an electronic tongue and nose. Such an effect was most likely underlain by changes in yeast fermentation activity, including decreased utilization of maltotriose and most amino acids, reduced production of isobutyl and isoamyl alcohols, and increased ethyl acetate content in the fungicide treated samples. Furthermore, yeast metabolic profiling by phenotype microarray and UPLC/TOF-MS showed that triadimefon caused significant changes in the metabolism of glutathione, phenylalanine and sphingolipids, and in sterol biosynthesis. Thus, triadimefon negatively affects beer sensory qualities by influencing the metabolic activity of S. cerevisiae during fermentation, emphasizing the necessity of stricter control over fungicide residues in brewing by the food industry. [less ▲]

Detailed reference viewed: 43 (3 ULiège)
See detailRôle des lymphocytes T TCR γδ dans la progression des lésions associées à l'infection par les papillomavirus humains
Van Hede, Dorien ULiege

Doctoral thesis (2017)

Cervical cancer was the fourth most frequent cancer in women in 2012, with the majority of cases occurring in less developed countries. Although this cancer is induced by Human Papillomavirus (HPV ... [more ▼]

Cervical cancer was the fourth most frequent cancer in women in 2012, with the majority of cases occurring in less developed countries. Although this cancer is induced by Human Papillomavirus (HPV) infections that have a high prevalence, only a very few percentage of infected women will developed this disease. Host immune defenses are essential to clear infection and to kill virus-infected transformed cells. Indeed, majority of infected women clear the virus within two years while immunocompromised patients are more likely to develop cervical preneoplastic lesions and cancers. γδ T cells have been shown to protect against the formation of squamous cell carcinoma (SCC) in several models. Nowadays, the contribution of γδ T cells in HPV associated uterine cervical SCC is unknown. Here we investigated the impact of γδ T cells in a transgenic mouse model of carcinogenesis induced by HPV16-oncoproteins. Surprisingly, γδ T cells promoted the development of HPV16-oncoprotein-induced lesions. These oncoproteins induced a decrease in epidermal Skint-1 expression and modification of the associated anti-tumor Vγ5+ γδ T cells (or DETC), which were joined by other γδ T cell subsets actively producing IL-17. Consistent with a proangiogenic role, γδ T cells promoted the formation of blood vessels in the dermis underlying the HPV-induced lesions. In human cervical, IL-17+ γδ T cells could be only observed at the cancer stage (SCC) (but not in less advanced cervical lesions), where HPV oncoproteins are highly expressed, supporting the clinical relevance of our observations in mice. Overall, our results suggest that HPV16-oncoproteins induce a reorganization of the local epithelial-associated γδ T cell Subpopulations thereby promoting angiogenesis and cancer development. [less ▲]

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See detailSpatial diversification of agroecosystems towards biological control of insect pests: A focus on intercropping and wildflower strips
Hatt, Séverin ULiege

Doctoral thesis (2017)

Facing the limits of input-intensive agriculture, agroecology aims at thinking ways to design a sustainable agriculture that is economically viable and socially relevant. It notably invites to mobilize ... [more ▼]

Facing the limits of input-intensive agriculture, agroecology aims at thinking ways to design a sustainable agriculture that is economically viable and socially relevant. It notably invites to mobilize ecological processes within agroecosystems in order to enhance the delivery of ecosystem services towards reducing the use of external inputs – among others insecticides. For enhancing biological control of insect pests, a strategy is to spatially diversify agroecosystems at the field scale. Whereas increasing plant diversity could directly negatively affect pest development on the one hand (i.e. bottom-up effect), providing flowering features could allow the enhancement of natural enemies and their direct effect on pest populations on the other hand (i.e. top-down effect). The present thesis focused on intercropping (i.e. the cultivation of at least two crop species simultaneously in a same field) as a way to diversify crop habitat, and the sowing of wildflower strips as a non-crop feature. A systematic analysis of the literature revealed that, in most of studies, wheat (Triticum aestivum L.)-based intercropping allows a reduction of insect pests on crops, without necessarily favouring their natural enemies, compared to pure-stands. Besides, the provision of flowering resources, by for instance sowing wildflower strips, can attract and support flower visiting predators and parasitoids. Hence, in a first set of field experiments, combining the two tactics of increasing crop diversity and providing flowering resources was tested. First in China, wheat crop was associated with oilseed rape (Brassica napus L.), but it neither allowed reducing aphid (Hemiptera: Aphididae) abundance nor enhancing their natural enemies compared to pure stands. Instead, aphid density – independently from the treatments – affected natural enemy abundance, and interspecific relations between aphids and their natural enemies were observed. Second in Belgium, wildflower strips were sown within a wheat field, which led to a reduction of aphid density in wheat plots in between flowering features and an increase of aphidophagous hoverflies (Diptera: Syrphidae) compared to pure-stand wheat. Nevertheless, the presence of flowering strips did not affect the other natural enemies, i.e. lacewings (Neuroptera: Chrysopidae), ladybeetles (Coleoptera: Coccinellidae) and parasitoid wasps (Hymenoptera: Braconidae). Therefore, a second set of field experiments focussed on ways to compose mixtures of wild flowers attractive to a diversity of natural enemies. Flower functional traits were considered due to their effect on insect behaviour. First, the hypothesis that mixtures with high functional diversity attract and support a high abundance and diversity of aphid flower visiting predators was tested. This hypothesis was not verified. Instead, the high density in the plots of some flower species (especially the Asteraceae Leucanthemum vulgare Lam.) known to be attractive to flower visitors was supposed to have overwhelmed the effect of functional diversity. Second, a methodology was developed to identify which flower traits significantly affect natural enemy abundance – in this experiment parasitoids of oilseed rape beetle pests (i.e. Meligethes spp. [Coleoptera: Nitidulidae] and Ceutorhynchus spp. [Coleoptera: Curculionidae]) – in flower mixtures. Among seven traits, visual traits (i.e. colour, ultra-violet reflectance) and the one related to food availability (i.e. corolla morphology) were found to significantly affect parasitoid abundance. These results highlight that (i) increasing plant diversity at the field scale can – but not systematically – favour a reduction of insect pests, (ii) including flowering features can enhance some – but not all – of their natural enemies, and (iii) in order to compose flower mixes attractive to natural enemies, specific flower traits – rather than functional diversity at the mixture level – can be considered. These results are discussed in a broader perspective. Indeed, strategies to spatially diversify crop and non-crop habitats in agroecosystems are various, as well as the ways to compose, manage and design such habitats. Also, processes at larger scales than the field may be determinant. Moreover, insects are not the only pests, and pests are not the only biotic or abiotic elements that need to be regulated in agroecosystems. Controlling multiple pests simultaneously but also enhancing the provision of multiple regulating services represent challenges for future research in agriculture. [less ▲]

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See detailProxima Cen b: theoretical spectral signatures for different atmospheric scenarios
Defrere, Denis ULiege; Léger, Alain; Grenfell, John Lee et al

Speech/Talk (2017)

Proxima Cen b is possibly the nearest rocky exoplanet orbiting in the habitable zone of its star and might represent by consequent a formidable opportunity for astrobiology. In this presentation, we ... [more ▼]

Proxima Cen b is possibly the nearest rocky exoplanet orbiting in the habitable zone of its star and might represent by consequent a formidable opportunity for astrobiology. In this presentation, we discuss several possible atmospheric compositions and present the corresponding infrared spectrum computed with modern planetary atmosphere models. To be specific, we consider (1) a bare planet, which has lost its atmosphere; (2) a water-ocean planet; (3) an Earth-analog planet; and (4) a planet similar to Earth but with a lower O2 pressure (< 1mbar) that produces a false positive for the triple signature (H20, O3, and CO2). We discuss the information contained in each infrared spectrum and the possibility to constrain the nature of the planet by remote sensing. We end this presentation by describing an instrumental concept recently proposed to ESA and optimised for this task. [less ▲]

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See detailCharacterizing exoplanetary atmospheres with a mid-infrared nulling interferometer
Defrere, Denis ULiege; Léger, Alain; Absil, Olivier ULiege

Speech/Talk (2017)

The discovery of an increasing number of terrestrial planets around nearby stars marks the dawn of a new era in the exoplanet field: the characterization and understanding of their atmospheres. To make ... [more ▼]

The discovery of an increasing number of terrestrial planets around nearby stars marks the dawn of a new era in the exoplanet field: the characterization and understanding of their atmospheres. To make significant progress, it becomes clear that a large number of exoplanetary atmospheres have to be studied at various wavelengths. This is particularly relevant for identifying possible bio-signatures. In this talk, we present a concept of a space-based mid-infrared nulling spectrograph that can characterize a large number of exoplanetary atmospheres and provide key information on their size, surface temperature, and the presence of key molecules such as CO2, H2O, CH4 and O3. The proposed mission concept would be particularly suited to characterize Proxima Cen b. [less ▲]

Detailed reference viewed: 22 (4 ULiège)
See detailIs going to space still worthwhile?
Rochus, Pierre ULiege

Conference (2017, June 27)

Very often, we hear: “Is it still worth going to space? Aren’t there better causes to spend our money on, here on Earth?” At this talk, Pierre Rochus will highlight the importance of the benefits that ... [more ▼]

Very often, we hear: “Is it still worth going to space? Aren’t there better causes to spend our money on, here on Earth?” At this talk, Pierre Rochus will highlight the importance of the benefits that space activities and space research bring. He will try to convince the credulous that besides those everyday space applications that we obviously can no longer do without (GPS, for instance!), space science activities are also essential for humanity. Space research not only gives answers to fundamental questions facing humanity but the technical design of future missions also poses a challenge to the collective imagination. Space scientific research is not only an intellectual challenge, it is much more: it is a stimulus for technical developments; it requires constant, leading-edge developments in different technical domains such as:  systems miniaturisation,  light detectors,  new materials,  coatings,  cryogenics,  mechanisms,  electrical motors,  tribology (the study of friction, wear, lubrication, and the design of bearings)  ... Space Research gives rise to spin-offs and unpredictable developments which will come in useful in our future daily life. One hope is that some part of the huge budgets dedicated to military research could be transferred to space activities. And, of course, it is very important to convince young people to study sciences and technology - where better to start, than in space? [less ▲]

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See detailAtmospheric free acidity from cloud processing
Franco, Bruno ULiege; Taraborrelli, Domenico; Gromov, Sergey et al

Conference (2017, June 27)

Detailed reference viewed: 36 (4 ULiège)
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See detailCharacterizing the leaching of sperrylite (PtAs2) in cyanide-based solutions
Mwase Malumbo, James ULiege; Petersen, Jochen

in Hydrometallurgy (2017)

The mineral sperrylite (PtAs2), unlike other Pt minerals, has shown to be resistant to cyanide leaching, even at elevated temperatures of 50 °C. This has prevented further development of a two-stage heap ... [more ▼]

The mineral sperrylite (PtAs2), unlike other Pt minerals, has shown to be resistant to cyanide leaching, even at elevated temperatures of 50 °C. This has prevented further development of a two-stage heap leaching process, of which the second stage is cyanide leaching for a Platreef ore, due to a considerable portion of the Pt being present as sperrylite. Through a comprehensive set of leaching tests, this study has shown that sperrylite leaches slowly in cyanide due to eventual passivation. The addition of ferricyanide to the cyanide solution results in significantly more Pt being leached (up to 16 times) than with cyanide only under identical process conditions. However, over time passivation occurred in this system also, but can be seemingly be overcome by filtering, rinsing and re-suspending the sperrylite. This was further investigated using a reactor system continuously fed with a ferricyanide-cyanide to leach a fixed bed of sperrylite mineral. Again, gradual passivation of the mineral phase was observed, which was fully reversible following a day of feeding with distilled water. XPS analysis of fresh and leached mineral indicated a depletion of As on the mineral surface, which tallied with an observed preferential leaching of As during leaching, at least initially. As a result, it is postulated that a less cyanide-soluble compound of the form PtAs(X) forms, where x is < 2. The ease with which the leaching process can be restarted after rinsing the mineral indicates that the adsorption of solution species is the key step in forming a passivating layer. This adsorption is potentially favoured by the gradual surface transformation. Finally, an electrochemical study confirmed that the ferricyanide-cyanide system facilitated an electron transfer reaction at the sperrylite surface with the likely oxidation of As and reduction of the ferricyanide. Gradual passivation of the surface was also observed in this system. [less ▲]

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See detailChine-Costa Rica. La projection des normes chinoises en Amérique centrale
Wintgens, Sophie ULiege

Conference (2017, June 27)

Cet article a pour hypothèse que l’accroissement des échanges économiques et commerciaux de la Chine avec le Costa Rica, premier pays membre du Système d’intégration centraméricain (SICA) à avoir signé un ... [more ▼]

Cet article a pour hypothèse que l’accroissement des échanges économiques et commerciaux de la Chine avec le Costa Rica, premier pays membre du Système d’intégration centraméricain (SICA) à avoir signé un accord de libre-échange avec Pékin, va de pair avec la projection des normes économiques et politiques chinoises en Amérique centrale. Afin de démontrer cette hypothèse, il article analyse les enjeux de la présence de la Chine au Costa Rica afin de voir si sa politique commerciale envers l’Amérique centrale est porteuse d’un projet économico-politique régional. [less ▲]

Detailed reference viewed: 13 (2 ULiège)