Last 7 days
Bookmark and Share    
Full Text
See detailMix and match: Essays on collective dynamics in nascent social entrepreneurship
Dufays, Frédéric ULg

Doctoral thesis (2016)

Social entrepreneurship is increasingly recognized both in research and practice as a form of entrepreneurship that is inherently hybrid as it combines a social-welfare logic with a commercial logic at ... [more ▼]

Social entrepreneurship is increasingly recognized both in research and practice as a form of entrepreneurship that is inherently hybrid as it combines a social-welfare logic with a commercial logic at its core. Collective dynamics, whether they point at an networked individual or a team, appear particularly salient both in the discourse on social entrepreneurship and in its practice. These would constitute a distinguishing feature of social entrepreneurship, which this dissertation examines through a set of four related research papers. First, social entrepreneurship as generically collective is taken as a starting point to review the literature. In particular, it identifies how the social network concept is used in relation to social entrepreneurship and develops research proposals aiming to explain social entrepreneurship emergence through this lens. Considering the entrepreneurial team as a crystallized social network that allows for bridging distinct logics constitutes one of these proposals, which is further explored in the second paper. Grounded in institutional theory, it develops a processual model describing how hybridity emerges and sustains throughout the entrepreneurial process and suggests that the entrepreneurial team may be a carrier of hybridity. The empirical part of the dissertation examines particular moments of this process. The third paper questions the collective dimension by seeking individuals’ meanings of entrepreneuring in team in the context of social entrepreneurship. Located a bit further in time in the entrepreneurial process, the fourth paper looks at organizational tensions in social entrepreneurial teams and nascent social enterprises and seeks to portray the manifestations of hybridity. Overall, this dissertation contributes to institutional theory by exploring the emergence of hybrid organizations; to team entrepreneurship literature by unravelling its antecedents and by explaining tensions in a context of institutional complexity; and to knowledge on social entrepreneurship by examining its collective dynamics at the early stages of the process. [less ▲]

Detailed reference viewed: 103 (17 ULg)
Full Text
See detailFirst come first served: “priority effect“ benefits Ambrosia artemisiifolia L. more than other ruderal Asteraceae species
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

Poster (2016, September 14)

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of ... [more ▼]

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of central and southern France, and northern Italy. Northwards beyond the edge of this range, occurrence of casual population have been described for years, but these populations do not appear to become invasive, and the species does not seem to spread. This situation raises the following question: Has the invaded range reached a limit or will the species continue its invasion northwards? To answer this question, we followed two complementary approaches. First we set up an experimental garden in Belgium, 250 km north to the current invaded range, to see if the local climate allows the completion of the species reproduction cycle. Second, we performed an in situ measurement campaign in 12 population located beyond the edge, within the range but near the margin, and in the center of the invaded range. The aim of this campaign was to test whether the species had reduced plant performance towards range margins. The results showed that the species is able to establish populations with high growth rates in Belgium. Furthermore, the species expressed similar performance across the considered areas, even beyond the current invasion front. No evidence of processes constraining the invasion was found, which suggests a great potential for invasion north to the current invaded range. In this uncertain situation, awareness actions should be considered in the northern countries. [less ▲]

Detailed reference viewed: 359 (215 ULg)
Full Text
Peer Reviewed
See detailPredicting the dynamic impact behaviour of spray droplets on flat plant surfaces
Delele, Mulugeta Admasu; Nuyttens, David; Douga, Ashenafitilahun T. et al

in Soft Matter (2016), 12 (34)(7), 195-211

The dynamic impact behaviour of water droplets on plant surfaces was investigated based on a multiphase computational fluid dynamics (CFD) model. The study was conducted using the Volume Of Fluid (VOF ... [more ▼]

The dynamic impact behaviour of water droplets on plant surfaces was investigated based on a multiphase computational fluid dynamics (CFD) model. The study was conducted using the Volume Of Fluid (VOF) approach. The static contact angle of water droplets on leaf surfaces of different plants (apple, pear, leek and cabbage) was measured and found to vary between 54.9 and 138.2°. Impact experiments were conducted by monitoring the flow and impact characteristics of water droplets on leaves in still air with a high speed camera. Droplets were generated by an agricultural flat fan spray nozzle moving across the leaf at constant speed. The nozzle produced droplets with diameters ranging from 20.6 up to 550.8 μm, and droplet velocity values near the impact between 0.03 and 13.2 m s(-1). The CFD model was capable of predicting the observed dynamic impact behaviour of droplets on the plant surfaces. The fate of the droplets after the impact process for adhesion, bouncing or splashing was accurately predicted for Weber numbers (We) in the range of 0.007 to 1096 and droplet Reynolds numbers (Re) between 5 to 8000. The process was highly dependent on the surface and droplet flow characteristics during the impact. Combinations of We, Re and Ohnesorge (Oh) numbers defined the droplet maximum spread factor, the number of secondary droplets generated as a result of the splashing process and the transition between the different impact outcomes. These criteria can then be used in field scale spray deposition and drift models to better understand agricultural spray operations. [less ▲]

Detailed reference viewed: 14 (1 ULg)
Full Text
See detailMonitoring water and pollutant leaching at an industrial site using geophysics and a vadose zone monitoring system.
Fernandez de Vera, Natalia ULg

Doctoral thesis (2016)

The development of protection and remediation plans for contaminated soil and groundwater require a detailed understanding of water flow dynamics and contaminant distribution in the subsurface. However ... [more ▼]

The development of protection and remediation plans for contaminated soil and groundwater require a detailed understanding of water flow dynamics and contaminant distribution in the subsurface. However, the retrieval of such information across the vadose zone is challenging, as most field technologies have limited accessibility beyond the first meters of subsoil and industrial environments pose additional technical difficulties for installation. The research presented here aims to provide effective in situ characterization tools that are capable of providing information about water flow dynamics, contaminant distribution and chemistry across the vadose zone of industrial contaminated sites. The Vadose Zone Monitoring System (VMS) was selected in conjunction with geophysical methods (Electrical Resistivity Tomography), given their adaptability for installation in polluted industrial sites. The VMS allows retrieval of in situ continuous hydraulic and chemical information of infiltrated water at different depths of the vadose zone through customized sensors installed in a slanted borehole. The spatial resolution of the subsurface is improved with geophysical methods, which are used to characterize structural heterogeneities in the subsurface and the spatial distribution of solutes therein. The setup containing both the VMS and a geophysical system was installed at a former industrial contaminated site in the west of Belgium. Soil and groundwater at the study site are contaminated with heavy metals, Polycyclic Aromatic Hydrocarbons (PAH) and inorganic contaminants, among others. Upon installation, the site was monitored under natural recharge conditions. Results from water content sensors installed in the VMS reveal quick rises in water content as a response to rainfall events to depths reaching 3.65m. From such water fluctuations, macropore, micropore, matrix and preferential flow mechanisms are identified. At greater depths, slower flow dynamics and matrix mechanisms are dominant. Results from sampled waters across the vadose zone reveal the existence of two predominant chemical facies at different depths, which are related with water infiltration flow mechanisms. Ni is identified as the main contaminant that is leaching across the vadose zone. Subsequent to such initial monitoring period, a saline tracer test was infiltrated on site and monitored via surface, cross-borehole ERT methods and the VMS to simulate the transport of a contaminant across the vadose zone. Results from a short term monitoring period (5 days) reveal the formation of a plume in the first meter of the subsurface. Slow vertical flow through matrix is found to be dominant. Measurements carried out 105 days after tracer infiltration vertical transport of the tracer towards depths that reached 4m. Results obtained from the VMS indicate that the tracer has reached such depths through the activation of matrix and fracture flow mechanisms following frequent rainfall episodes. The implementation of the setup has provided detailed information about water flow dynamics and chemistry across the vadose zone, as well as the spatial characterization of structures and tracer distribution in the subsurface. From such outcome, it can be concluded that this setup could be used to improve site conceptual models which are essential for developing risk assessments and remediation plans. [less ▲]

Detailed reference viewed: 27 (6 ULg)
Peer Reviewed
See detailSemi-continuous fermentation of a thermotolerant and high acetic acid producing Acetobacter pasteurianus bacterium
Mounir, Majid ULg; Thonart, Philippe; Ismaili Alaoui, Mustapha et al

Conference (2016, September 14)

Among 63 strains isolated from fruits and homemade vinegars from different ecosystems of Morocco, a thermotolerant bacterium with high production of acetic acid was selected and evaluated for its ability ... [more ▼]

Among 63 strains isolated from fruits and homemade vinegars from different ecosystems of Morocco, a thermotolerant bacterium with high production of acetic acid was selected and evaluated for its ability to perform efficient acetous fermentation at high temperature in a bioreactor. CV01 strain, isolated from cactus (Opuntia ficus-indica), was considered to be an Acetobacter pasteurianus sp. according to phylogenetic study based on 16s rDNA gene sequence analysis. An optimal culture medium containing initial concentrations of acetic acid and ethanol of 1% (v/v) and 4% (v/v), respectively, was used. The growth kinetics of this isolate were monitored in flasks and compared with those of the wild type LMG 1625 mesophilic strain and the thermoresistant Acetobacter senegalensis reference strain. The CV01 strain exhibited abundant growth along with high amount of produced acetic acid at high temperature (41°C). Subsequently, a 20-L stirred tank bioreactor was used to assess thermotolerance and acidoresistance properties of the selected strain during semi-continuous acetic acid fermentation at 38°C. Interestingly, a total amount of 13.4% (w/v) acetic acid was yielded at the end of fermentation. Moreover, this bacterium could produce during the same fermentation process a final concentration of 11.2 g/L gluconic acid, a sensory quality indicator in vinegar production. Finally, the enzymatic study showed that CV01 strain exhibited high ADH and ALDH enzyme activity at 38°C compared with the mesophilic reference strain LMG 1632, which was significantly susceptible to thermal inactivation. [less ▲]

Detailed reference viewed: 22 (1 ULg)
Full Text
See detailMethods and models for brain connectivity assessment across levels of consciousness
Amico, Enrico ULg

Doctoral thesis (2016)

The human brain is one of the most complex and fascinating systems in nature. In the last decades, two events have boosted the investigation of its functional and structural properties. Firstly, the ... [more ▼]

The human brain is one of the most complex and fascinating systems in nature. In the last decades, two events have boosted the investigation of its functional and structural properties. Firstly, the emergence of novel noninvasive neuroimaging modalities, which helped improving the spatial and temporal resolution of the data collected from in vivo human brains. Secondly, the development of advanced mathematical tools in network science and graph theory, which has recently translated into modeling the human brain as a network, giving rise to the area of research so called Brain Connectivity or Connectomics. In brain network models, nodes correspond to gray-matter regions (based on functional or structural, atlas-based parcellations that constitute a partition), while links or edges correspond either to structural connections as modeled based on white matter fiber-tracts or to the functional coupling between brain regions by computing statistical dependencies between measured brain activity from different nodes. Indeed, the network approach for studying the brain has several advantages: 1) it eases the study of collective behaviors and interactions between regions; 2) allows to map and study quantitative properties of its anatomical pathways; 3) gives measures to quantify integration and segregation of information processes in the brain, and the flow (i.e. the interacting dynamics) between different cortical and sub-cortical regions. The main contribution of my PhD work was indeed to develop and implement new models and methods for brain connectivity assessment in the human brain, having as primary application the analysis of neuroimaging data coming from subjects at different levels of consciousness. I have here applied these methods to investigate changes in levels of consciousness, from normal wakefulness (healthy human brains) or drug-induced unconsciousness (i.e. anesthesia) to pathological (i.e. patients with disorders of consciousness). [less ▲]

Detailed reference viewed: 27 (1 ULg)
Peer Reviewed
See detailExtremophile plants as source of biopesticides against European damageable plant pathogens
Ben Kaab, Sofiène ULg; Parisi, Olivier ULg; De Clerck, Caroline ULg et al

Poster (2016, September 14)

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments (Pane et al., 2016). Unfavorable environmental conditions (such as salt ... [more ▼]

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments (Pane et al., 2016). Unfavorable environmental conditions (such as salt and drought) increase production and accumulation of reactive oxygen species (ROS). Consequently, extremophile plants have developed adaptive responses including the synthesis of specific bioactive molecules used for medical and nutritional purposes (Ksouri et al., 2012). In that context, the main objective of the present study was the identification of effective plant extracts and essential oils from extremophile plants against the most important plant pathogens in Europe (in term of loss, treatment necessity and/or cost). The study began with the selection of four endemic medicinal species suspected to be antimicrobial due to their wealth of phenolic and terpene compounds, such as flavonoids, phenolic acids, and coumarins (Ksouri et al., 2012). Each of the aerial plant materials was grounded and macerated with solvent (methanol or chloroform) for 24 h. The solvent was then eliminated along rotavapor. The yield of plant extract varied between 1.56 and 6.7%. Kinetics of growth of the 3 pathogens cultivable in liquid medium was determined before testing the impact of plant extracts and essential oils. Methanolic and chloroform plant extracts (EM1, EM2, EC1 and EC2) and essential oils (EO1, EO2) were compared for their antifungal potential. The chemical composition of the essential oils obtained by hydrodistillation from the aerial parts was analyzed by GC/MS. Yield of essential oil varied between 0.7 and 1.2%. Therefore, antifungal activity of plant extracts and essential oils was evaluated using ELISA microplates with a blocked randomized design, as described previously (Parisi et al., 2013). The results obtained showed that EM2 at 7 mg/ml has a very high fungistatic activity against Fusarium culmorum, F. oxysporum and Penicillium italicum. It was characterized with a high amount of polyphenols, flavonoids and condensed tannins. Statistical analysis showed that the efficiency of methanol extracts significantly differed from those of the chloroform extracts. In addition, essential oils significantly reduced spores germination in a dose-dependent manner. Their fungistatic activity reached 100% at 6000 ppm. In conclusion, this work allowed us to open new perspectives on the application of extremophile plant extracts as novel biocontrol strategy against plant pathogens. [less ▲]

Detailed reference viewed: 46 (13 ULg)
See detailWhat’s with the hyphens? A social studies perspective on science-technology-society
Van Oudheusden, Michiel ULg

Scientific conference (2016, September 13)

This presentation highlights the roles social scientists (notably in the field of science and technology studies) can/should play in nuclear research and development. Three cases are briefly described and ... [more ▼]

This presentation highlights the roles social scientists (notably in the field of science and technology studies) can/should play in nuclear research and development. Three cases are briefly described and assessed: citizen science after Fukushima, incident reporting at the Belgian Nuclear Research Centre SCK-CEN, and the "microbiologization" of radioactive waste management. [less ▲]

Detailed reference viewed: 19 (1 ULg)
See detailOrganocatalytic ring-opening polymerization towards polyphosphoesters
Clément, Benoit; Vanslambrouck, Stépanie; Carion, Stéphan ULg et al

Conference (2016, September 13)

Hydrolytically degradable and biocompatible aliphatic polyesters are widely applied for biomedical applications as implants, scaffolds for tissue engineering and, finally, as nanocarriers for drug ... [more ▼]

Hydrolytically degradable and biocompatible aliphatic polyesters are widely applied for biomedical applications as implants, scaffolds for tissue engineering and, finally, as nanocarriers for drug delivery. Aliphatic phophoesters, known since the pioneering work of S. Penczek in the 70’s, exhibit the same properties of hydrolytic degradability and biocompatibility and are thus more and more studied for biomedical applications as well. In the field of materials, anti-fire properties opens up new perspectives. The difference between polyesters and polyphosphoesters in terms of synthesis and properties will be highlighted. Polyphosphosphoesters are synthesized by step-growth and chain growth polymerization. When these polyphosphoesters are synthesized by ring-opening polymerization of cyclic phosphoesters, organocatalysts turned out to be very efficient compared to coodination processes. The last part of the talk will deal with te implementation of ROP of cyclic phosphates towards a series of amphiphilic PEO-block-polyphosphate copolymers of tailored hydrophobicity depending on the length of the lateral alkyl group. These polymers are able to self assemble into nanoparticles by direct dissolution in water, thus in the absernce of any organic solvent. The so-obtained micelles were studied by a set of techniques (Pyrene Fluorescence, Dynamic Light Scattering, Tensiometry). Finally, the influence of the hydrophobicity of the polyphosphate block of the micelle on the encapsulation and the release of a model drug was investigated. [less ▲]

Detailed reference viewed: 46 (7 ULg)
Full Text
See detailIs Ambrosia artemisiifolia L. able to expand its invaded range northward in Western Europe?
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

Conference (2016, September 13)

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of ... [more ▼]

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of central and southern France, and northern Italy. Northwards beyond the edge of this range, occurrence of casual population have been described for years, but these populations do not appear to become invasive, and the species does not seem to spread. This situation raises the following question: Has the invaded range reached a limit or will the species continue its invasion northwards? To answer this question, we followed two complementary approaches. First we set up an experimental garden in Belgium, 250 km north to the current invaded range, to see if the local climate allows the completion of the species reproduction cycle. Second, we performed an in situ measurement campaign in 12 population located beyond the edge, within the range but near the margin, and in the center of the invaded range. The aim of this campaign was to test whether the species had reduced plant performance towards range margins. The results showed that the species is able to establish populations with high growth rates in Belgium. Furthermore, the species expressed similar performance across the considered areas, even beyond the current invasion front. No evidence of processes constraining the invasion was found, which suggests a great potential for invasion north to the current invaded range. In this uncertain situation, awareness actions should be considered in the northern countries. [less ▲]

Detailed reference viewed: 36 (12 ULg)
See detailInvestigating the effect of plant-derived amendments on PAHs degradation in brownfield contaminated soils
Davin, Marie ULg; Starren, Amandine ULg; Colinet, Gilles ULg et al

Conference (2016, September 13)

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistant organic compounds of major concern that tend to accumulate in the environment, damaging ecosystems and health. Brownfields represent an ... [more ▼]

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistant organic compounds of major concern that tend to accumulate in the environment, damaging ecosystems and health. Brownfields represent an important tank for PAHs that require remediation. As an alternative to environmentally aggressive, expensive and often disruptive soil remediation strategies, experiences have been carried on to understand and develop techniques based on bioremediation and phytoremediation. PAHs degradation experiments were conducted in microcosms (laboratory scale) in order to determine whether several plant-derived amendments could enhance bioremediation. Briefly, samples of aged contaminated soils were treated with different concentrations of Medicago sativa or Trifolium pratense root exudates or dried roots, commercial saponin, a natural surfactant found in some plant roots such as some Fabaceae, and some samples were left unamended as controls. Soil samples were incubated for two and four weeks at controlled temperature (28°C). Carbon dioxide emission was monitored throughout the whole incubation. At the end of each experiment, dehydrogenase activity was measured as an indicator of microbiological activity and residual PAHs were determined using High-Performance Liquid Chromatography with Fluorimetric Detection (HPLC-FLD). In total, eleven amendment modalities and two incubation periods were tested and repeated four times. Preliminary experiments show promising results as amended samples seem to show different respiration activities. Ongoing studies will allow discussion as to whether or not PAHs degradation is influenced by the different modalities and if there are any differences according to the nature and concentration of the amendment. [less ▲]

Detailed reference viewed: 41 (2 ULg)
Full Text
Peer Reviewed
See detailRaised interferon beta, type 3 interferon and interferon stimulated genes - evidence of innate immune activation in neutrophilic asthma.
da Silva, J.; Hilzendeger, Clarissa ULg; Moermans, Catherine et al

in Clinical & Experimental Allergy : Journal of the British Society for Allergy & Clinical Immunology (2016)

BACKGROUND: Interferons play an important role in innate immunity. Previous studies report deficiency in virus-induction of interferon (IFN)-alpha, -beta and -lambda in bronchial epithelial and bronchial ... [more ▼]

BACKGROUND: Interferons play an important role in innate immunity. Previous studies report deficiency in virus-induction of interferon (IFN)-alpha, -beta and -lambda in bronchial epithelial and bronchial lavage cells in atopic asthmatics. It is now recognized that asthma is a heterogeneous disease comprising different inflammatory phenotypes, some of which may involve innate immune activation in the absence of overt infection. OBJECTIVE: The aim of the study was investigate if the severity of asthma or a specific cellular sputum pattern may be linked to evidence of innate immune activation. METHODS: Here we investigate the expression of IFN-beta, IFN-lambda1 (IL-29), IFN-lambda2/3 (IL-28A/B) and the interferon-stimulated genes (ISGs) myxovirus resistance 1 (Mx1), oligoadenylate synthetase (OAS) and viperin in unstimulated sputum cells in 57 asthmatics (including 16 mild, 19 moderate and 22 severe asthma patients) and compared them with 19 healthy subjects. RESULTS: We observed increased expression of IFN-beta, IFN-lambda1/IL-29, OAS and viperin in asthmatic compared to healthy subjects while IL-28 was not expressed in any group. The overexpression was restricted to neutrophilic asthmatics (sputum neutrophils >/= 76%) while eosinophilic asthmatics (sputum eosinophils >/= 3%) did not differ from healthy subjects or even showed a lower expression of Mx1. No difference in interferon or ISG expression was seen according to clinical asthma severity. CONCLUSION AND CLINICAL RELEVANCE: Neutrophilic, but not eosinophilic, asthmatics display overexpression of IFN-beta, IFN-lambda1/IL-29 and ISGs in their sputum cells that may reflect ongoing innate immune activation. This article is protected by copyright. All rights reserved. [less ▲]

Detailed reference viewed: 13 (3 ULg)
Full Text
Peer Reviewed
See detailDirect measurement of evapotranspiration from a forest using a superconducting gravimeter
Van Camp, Michel; de Viron, Olivier; Pajot-Métivier, Gwendoline et al

in Geophysical Research Letters (2016), 43

Evapotranspiration (ET) controls the flux between the land surface and the atmosphere. Assessing the ET ecosystems remains a key challenge in hydrology. We have found that the ET water mass loss can be ... [more ▼]

Evapotranspiration (ET) controls the flux between the land surface and the atmosphere. Assessing the ET ecosystems remains a key challenge in hydrology. We have found that the ET water mass loss can be directly inferred from continuous gravity measurements: as water evaporates and transpires from terrestrial ecosystems, the mass distribution of water decreases, changing the gravity field. Using continuous superconducting gravity measurements, we were able to identify daily gravity changes at the level of, or smaller than, 10-9 nms-2 (or 10-10 g) per day. This corresponds to 1.7mmof water over an area of 50 ha. The strength of this method is its ability to enable a direct, traceable and continuous monitoring of actual ET for years at the mesoscale with a high accuracy. [less ▲]

Detailed reference viewed: 20 (9 ULg)
Full Text
See detailDerecho constitucional comparado: observaciones desde la perspectiva europea
Colussi, Ilaria Anna ULg

Scientific conference (2016, September 13)

The conference was focused on Comparative Constitutional Law. The speech (in Spanish) was aimed at highlighting the object, methodology, nature, purpose of comparative constitutional law, and underline ... [more ▼]

The conference was focused on Comparative Constitutional Law. The speech (in Spanish) was aimed at highlighting the object, methodology, nature, purpose of comparative constitutional law, and underline current and future challenges of the field from the European perspective. An analysis of forms of State, of government and different types of Constitutions and legal systems is offered, as well as the convergence between systems of common law and civil law, and the actual tendencies of "osmosis" of human rights' protection. [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
See detailMethodik zur schnellen Bewertung von Syntheserouten auf Basis von Exergiebilanzen
Frenzel, Philipp; Pfennig, Andreas ULg

Conference (2016, September 13)

Heutige chemische Produkte basieren fast ausschließlich auf erdölbasierten Rohstoffen. Aufgrund weltweiter Bemühungen, die Abhängigkeit von fossilen Rohstoffen zu reduzieren, wird in den letzten Jahren ... [more ▼]

Heutige chemische Produkte basieren fast ausschließlich auf erdölbasierten Rohstoffen. Aufgrund weltweiter Bemühungen, die Abhängigkeit von fossilen Rohstoffen zu reduzieren, wird in den letzten Jahren verstärkt die Nutzung alternativer Kohlenstoffquellen wie Biomasse oder CO2 erforscht. Die alternativen Kohlenstoffquellen unterscheiden sich hinsichtlich ihrer Zusammensetzung und Stoffeigenschaften teilweise deutlich von fossilen Rohstoffen. Aus diesem Grund müssen Syntheserouten und darauf aufbauende Prozesse neu entwickelt werden. Da zum einen sehr viele Syntheserouten prinzipiell denkbar sind und zum anderen die Entwicklung der entsprechenden Prozesse aufwendig ist, wird eine Möglichkeit benötigt, begrenzte Entwicklungsressourcen sinnvoll zu steuern. Dazu sollte bereits in einem frühen Entwicklungsstadium ein quantitativer Vergleich der Syntheserouten erfolgen, um diejenigen zu identifizieren, die das größte wirtschaftliche Potential versprechen. In diesem Vortrag wird eine Methodik vorgestellt, um eine schnelle erste, auf Exergie basierte Bewertung des wirtschaftlichen Potentials einer Syntheseroute bereits in einem frühen Entwicklungsstadium durchzuführen, in dem nur wenige Informationen vorliegen. Die Idee der Methodik ist, Syntheserouten in standardisierten Prozessen abzubilden, wodurch eine automatisierte Auswertung und somit ein schnelles Screening möglich wird. Die standardisierten Prozesse umfassen sowohl den Einfluss der Reaktion durch Abbildung der Reaktionsbedingungen, Stöchiometrie, Umsatz und Selektivität als auch die Auswirkungen der Trennaufgabe. Ebenso berücksichtigt wird die Rückführung von Lösungsmitteln und ggf. nicht umgesetzten Edukten. Als zentrale Bewertungsgröße zur Abschätzung des wirtschaftlichen Potentials wird eine Kombination aus Exergie- und Rohstoffeinsatz herangezogen. Der Vorteil von Exergiebilanzen gegenüber Energiebilanzen ist, dass die Produktion von Entropie berücksichtigt wird und so die Auswirkungen einzelner Prozessschritte untersucht und zwischen verschiedenen Energieformen unterschieden werden kann. Durch Berechnung der Exergieverluste, also der Verluste von Exergie aufgrund von Entropieerzeugung in den Prozessen, ergibt sich ein quantitativer Vergleich verschiedener Syntheserouten. [less ▲]

Detailed reference viewed: 10 (0 ULg)
Full Text
See detailDynamics of ligands on gold surface to obtain Janus nanoclusters: A theoretical and experimental investigation
Lugo Preciado, Jesús Gustavo ULg

Doctoral thesis (2016)

We performed a joint computational – experimental investigation of the dynamics of ligand exchange on gold nanoclusters (GNC) surface with the aim to understand how to control the structural and optical ... [more ▼]

We performed a joint computational – experimental investigation of the dynamics of ligand exchange on gold nanoclusters (GNC) surface with the aim to understand how to control the structural and optical properties of GNC through the design of their ligand shell. Our computational studies were carried out in the framework of the Kohn – Sham implementation of density functional theory in quantum chemistry. We analyzed the main features of UV – Vis spectra computed at the TD – DFT / CAM – B3LYP level for the Au13, Au25, and Au28 metallic cores protected by thiolate, chloride, and phosphine ligands. Our results show that it is possible to tune the energy of the lowest absorption band of gold clusters by ligand shell engineering in order to control the charge redistribution between ligand shell and metallic core. In parallel we synthesized a set of Au25(ATP)x(TP)18 – x clusters with different ATP/TP ratios using an adapted Demessence protocol by combining 4ATP (4 – aminothiophenol) and TP (thiophenol) ligands. ESI – MS measurements evidence that for these mixed ligand shells the Au25 nuclearity is preserved. However, the addition of the DDT (1 – dodecanethiol) ligand in the mixture leads to nanoparticle formation. FT – IR spectroscopy confirms the absorption of two different ligands on the gold surface and SAXS shows that we have a good correlation between the distance between two clusters and the length of the ligand protecting them. Furthermore, we collaborated with the Institut Charles Gerhardt in the Université de Montpellier, France whose experimental results show that several n – heterocyclic carbenes (NHC) bearing different groups on the N atoms exhibit similar reactivity when protecting a gold nanosurface. The formation of the bis(NHC) AuI gold complexes is evidenced by 13C NMR. In order to complement and interpret the experimental results, we carried out a computational study of the adsorption of a single NHC on Au38 which acts as a model for the gold surface, as well as of the fully NHC ligated Au38 cluster. The joint experimental – theoretical study, in particular the comparison between computed and 13C NMR spectra allows proposing a possible mechanism explaining the formation of [NHC – Au – NHC]+ complexes and the erosion experienced by the nanoparticle. Finally, we carried out a comparison of the mode of binding and the structural and optical properties of the fully ligated PH3 and NHC GNC with metallic cores of different nuclearities. Our computations show that the Au – P bond is weaker than the Au – NHC one. Additionally, our study confirms that the ligand – to – metal charge transfer is an important parameter for understanding the electronic transitions and the UV – Vis spectra in these clusters. Our computations on the PH3 – Au38 set of complexes show that there is a site selectivity for the reactivity for the PH3 interacting on the Au38 surface which allows predicting where the PH3 is likely to be adsorbed. This selectivity is not observed in the case of the binding of a single NHC ligand on the surface of the Au38 cluster. [less ▲]

Detailed reference viewed: 29 (5 ULg)
See detailUn demi-siècle d''exploration de la planète Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2016)

Detailed reference viewed: 23 (1 ULg)
Full Text
Peer Reviewed
See detailEffects of equine chorionic gonadotropin (eCG) on the sexual behaviour and ovulatory characteristics of female african N'Dama cattle.
Okouyi, M.W. Marcel; Hanzen, Christian ULg

in Revue de Médecine Vétérinaire (2016), 167(7-8), 211-215

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days ... [more ▼]

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days (Controlled Internal Drug Released) and a PGF2α injection two days after the end of treatment. The animals were randomly split into a non-treated control group (n=26) and four groups with increasing doses of eCG: 300 IU (n=25), 400 IU (n=24), 500 IU (n=23) and 600 IU (n=23), which were injected on the day of CIDR withdrawal. The animals were then followed (24 hours a day) for six days. Oestrus was confirmed on the basis of identifying 'standing oestrus', i.e., when the cow stood to be mounted. Seven to ten days after the CIDR® was withdrawn, the animals were slaughtered, and their ovaries were examined to identify and count the number of follicular and/or luteal structures. The onset of heat was 48.6 ± 5.3 hours after eCG injection, and the average length of oestrus was 9.9 ± 2 hours. The eCG dosage had no significant effect on these two parameters. In contrast, the observed rate of oestrus was significantly (p<0.05) higher in animals that had been treated (70.8 to 84.0%) in comparison with animals that had not been treated (50%). Similarly, the ovulation rate was significantly (p<0.05) higher in treated animals (88.0 to 100%) than in untreated animals (73.1%). The percentage of animals that presented multiple ovulations increased significantly (p <0.001) with the dosage of eCG administered (4.5% to 36.4%). [less ▲]

Detailed reference viewed: 29 (13 ULg)