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See detailElectric current crowding effects in microstructured superconductors
Adami, Obaïd-Allah ULg

Doctoral thesis (2016)

Many applications of modern electronic devices are based on thin film geometries including sharp turns, holes and exhibiting inhomogeneities. The inevitable detour of current streamlines around such ... [more ▼]

Many applications of modern electronic devices are based on thin film geometries including sharp turns, holes and exhibiting inhomogeneities. The inevitable detour of current streamlines around such obstacles cause an inhomogeneous current density profile giving rise to current crowding. The goal of my research is to highlight the current crowding effects in micro and nanopatterned superconducting films. [less ▲]

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See detailNormative data on teachers’ voice use in real-life situations
Schiller, Isabel ULg; Morsomme, Dominique ULg; Alcoulombre, Anaëlle et al

Conference (2016, August 25)

Background As part of their working routine, teachers use their voice for extended periods of time. To compensate for adverse acoustic conditions and background noise, they are also required to speak at ... [more ▼]

Background As part of their working routine, teachers use their voice for extended periods of time. To compensate for adverse acoustic conditions and background noise, they are also required to speak at high intensities. Since teaching is acknowledged to be vocally demanding, several studies have investigated teachers’ vocal load, that is, the stress inflicted on the larynx during vocalization, which is thought to be influenced by duration, intensity and frequency of phonation. A promising method for analyzing teachers’ phonatory behavior in real-life situations is the use of a portable voice dosimeter that objectively documents vocal parameters. Depending on several factors, those parameters may vary within the teaching profession (Masuda et al., 1993; Morrow and Connor, 2011; Remacle, Morsomme, and Finck, 2014). With the aim of quantifying their vocal parameters and identifying the most at-risk teaching conditions, we have established a large database of French-speaking teachers. Based on this database, this study analyzed vocal loading differences with regard to gender, teaching level, and environment (professional versus extra-professional). Methods Seventy-six French-speaking teachers (15 males and 61 females) were monitored during one workweek using the Ambulatory Phonation Monitor voice dosimeter (KayPENTAX). The subjects included 21 kindergarten, 20 primary and 35 secondary school teachers. All male subjects were in the latter group. The vocal parameters analyzed were phonation time, intensity and fundamental frequency (F0). Results The statistical analysis revealed that, irrespective of gender, phonation time, F0 and intensity level were significantly higher in the professional environment than the extra-professional environment (p<.01). Among female subjects, the F0 of kindergarten teachers was significantly higher than that of primary school teachers, which in turn was higher than that of secondary school teachers (p<.01). The phonation time and intensity were also higher in female kindergarten teachers than other female teachers, but this difference did not reach significance. As expected, regarding gender differences, we found that female secondary school teachers spoke with significantly higher F0 than their male colleagues (p<.001). In the extra-professional setting, they also spoke with a significantly higher intensity (p<.05), but no such effect was found in the professional environment. Conclusion Overall, our subjects showed an increase in vocal loading parameters when they were at work compared to their free time. This confirms the results of earlier studies and demonstrates that teaching is an occupation with remarkably high vocal demands. The analysis of mean frequency showed that lower school levels were associated with higher-pitched voice. It can be assumed that kindergarten teachers adapt to the higher F0 of their young pupils and that their effort to maintain the pupils’ attention results in greater frequency variations. References Masuda, T., Ikeda, Y., Manako, H., & Komiyama, S. (1993). Analysis of vocal abuse: Fluctuations in phonation time and intensity in 4 groups of speakers. Acta Oto-Laryngologica, 113(3), 547–552. Morrow, S. L., & Connor, N. P. (2011). Comparison of voice-use profiles between elementary classroom and music teachers. Journal of Voice, 25(3), 367–372. Remacle, A., Morsomme, D., & Finck, C. (2014). Comparison of vocal loading parameters in kindergarten and elementary school teachers. Journal of Speech, Language, and Hearing Research, 57(2), 406–415. [less ▲]

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See detailEtude des sémiochimiques volatils impliqués dans le mutualisme fourmis-pucerons
Fischer, Christophe ULg

Doctoral thesis (2016)

For decades, the mutualistic relationship that ant and aphids may present has fascinated entomologists, as evidenced by the abundant literature on the subject. The principles of this interaction are ... [more ▼]

For decades, the mutualistic relationship that ant and aphids may present has fascinated entomologists, as evidenced by the abundant literature on the subject. The principles of this interaction are simple: as long as their colony remains, aphids provide ants with a stable and abundant source of sugars, honeydew. In exchange, ants tend aphid colonies and provide them cleaning and protection against various natural enemies. Nevertheless, some aspects of this relationship remain misunderstood. This is for example the case of the factors influencing the search and the discovery of a potential partner, first step to any potential mutualistic interaction. The role held by volatile chemical cues, called semiochemicals, in this relationship is also misunderstood. The objective of this thesis is to improve understanding of the role played by volatile semiochemicals in this mutualistic relationship, especially during the partner search stage, both from the perspective of the ant and of the aphid. The black garden ant, Lasius niger L., and the black bean aphid, Aphis fabae Scop., constitute our biological model. The impact of volatile compounds on the search behavior of the ant has first been investigated. These compounds are from multiple origins, either directly emitted by the aphid or induced by its presence. First, the ability of ants to perceive E-β-farnesene, the main component of many aphid alarm pheromone, and to use it to locate aphid colonies has been highlighted. This compound has indeed shown attractiveness to ants, even at low doses corresponding to the emissions of an unstressed aphid colony. Then, the roles played by honeydew volatile compounds in ant attraction have been demonstrated. These compounds also allow ants to remotely discriminate different aphid species and to direct their searches accordingly. These semiochemicals are produced by honeydew microflora, and a particularly attractive bacterial strain, Staphylococcus xylosus, has been isolated from A. fabae honeydew. Finally, the active role of winged aphids, which are aphid’s dispersal form, in the search for a mutualistic partner was also studied. Aphids do not appear to be preferentially attracted toward a host plant frequented by ants or close an ant nest. Nevertheless, once a potential host plant reached, they remain longer on it in case of ant presence. This thesis highlights the importance of volatile semiochemicals and honeydew microflora in ant-aphid mutualistic relationships, thus completing by a new aspect an already well documented biological model. [less ▲]

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See detailMESURES INCITATIVES A LA PRODUCTION COTONNIERE ET PERSPECTIVES DE LA PRIVATISATION DES FILIALES CMDT AU MALI
Koné, Bouréma ULg

Doctoral thesis (2016)

Cotton is the first export crop in Mali with 84,370 billion Fcfa in 2010 (INSTAT, 2010), but the production of this crop has huge problems due to external factors (prices of inputs and seed cotton) and ... [more ▼]

Cotton is the first export crop in Mali with 84,370 billion Fcfa in 2010 (INSTAT, 2010), but the production of this crop has huge problems due to external factors (prices of inputs and seed cotton) and internal (within payment to producers, internal debts of cooperatives). To boost cotton production during the years 2010/11 and 2011/12, the government had maintained the level of fertilizer subsidy at 50% of normal price on the market. In addition to this level of subsidy, the incentive price of 255Fcfa / kg was fixed to the producer and the National Union of Cotton Producers Cooperative Societies (NU-CPCS) facilitated the clearance of the internal debts of cooperatives. Despite the fall in world prices after 2011/12, the price of cotton seed remains little changed. The price stayed at 255 CFA francs / kg in 2012/13 and got back to 250 CFA francs / kg in 2013/14. The objective of this work is to analyze the effects of incentives factors cotton production with a view to the privatization of CMDT subsidiaries Surveys were conducted with a sample of 240 farms selected from the four zones of the CMDT zones based on two villages subsidiary during the years of 2008/09, 2010/11 and 2011/12. The results showed a positive trend in production (mainly due to an increase in the area) and in the income of cotton producers with a higher reimbursement rate of input credits under cultivation. The analysis of the Domestic Resource Cost (DRC) the Nominal protection coefficients (NPC) and the Effective (CPE) showed an improvement in thèse variables in 2011/12 with the incentive policy. An analysis of the determinants of the supply of cotton showed that only two variables were significant: the price cottonseed and payment period. The incentive factors are influenced by fiber market in 2011/12 which took a downward trend from the campaign. This incentive policy being favored by the market of fiber which is very unstable, it would be necessary to create conditions in which the producer can benefit from the price obtained on the quality of fiber to maintain the incentive policy for producers. For the privatization of Cotton Company, an upgrade of this company is necessary with the support of the Malian state. But this upgrade should not affect too much the selling price of sale of cotton that can bring new companies in a situation of too long term recovery of capital invested (long period of investment recovery). The privatization scheme as presented makes major companies more competitive. In order to reduce the operating costs a form of collaborative relationships among delivery companies would be required. Keywords: fertilizer subsidy, incentive price, cotton sector in Mali, privatization subsidiary, competitiveness. [less ▲]

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See detailOccurrence rates of invasive plants in limestone quarries (Southern Belgium)
Pitz, Carline ULg; Jorion, Alexis ULg; Mahy, Grégory ULg et al

Conference (2016, August 23)

In quarries, invasive plant species can slow down the installation of high conservation value vegetation. Successful management of invasive requires, at first, a quantitative assessment of invasion levels ... [more ▼]

In quarries, invasive plant species can slow down the installation of high conservation value vegetation. Successful management of invasive requires, at first, a quantitative assessment of invasion levels. Although European legislation has adopted an ambitious strategy against invasive species, there is still a lack of knowledge about their occurrence in quarries. The aim of this study was to evaluate occurrence rates of invasive plant species in limestone quarries throughout Wallonia (Southern Belgium) and identify high priority and emerging invasive plants for adapted management. During 2016 vegetation period, forty quarries were selected by stratified sampling, using abandoned and active quarries as strata. Within selected quarries, two-meter wide transects were established to cross all activity sectors. Transects were divided in 10x2m plots, resulting in 2% of total surface of each quarry being surveyed. Cover and number of individuals of invasive plants species were recorded in each plot. Species considered were those of Harmonia list (67 species), the reference at the Wallonia scale. More than 30 000 plots were surveyed. Results of our recent study are presented (occurrences rates by species, mean percentage cover per site). First results indicate that dominant invasive species originate from different introduction paths: (i) planted (Robinia pseudoacacia); (ii) ornamentals (Cotoneaster horizontalis) and (iii) spontaneous colonization (Senecio inaequidens) - and follow various invasion dynamics. We propose research and management methods to be directed towards limitation of top ten frequent species (e.g. Buddleia davidii, Senecio inaequidens), and to establish a detection system for the emerging invasive plants. [less ▲]

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See detailDevelopment of innovative and practical management tools to improve sustainability of milk production and quality of dairy products
Arnould, Valérie ULg

Doctoral thesis (2016)

In the current complex economical context, novel strategies are needed to help local dairy farmers to face the European dairy sector crisis. This thesis was initiated in the framework of ManageMilk ... [more ▼]

In the current complex economical context, novel strategies are needed to help local dairy farmers to face the European dairy sector crisis. This thesis was initiated in the framework of ManageMilk project and was globally aimed to investigate the possibility to develop some innovative and practical management tools helping dairy farmers in their daily decisions. To develop such management tools, several conditions must be fulfilled. Firstly, used data must be relevant. According to the literature, the milk composition, and in particular, the milk fatty acid (FA) profile, appears to be a suitable trait allowing useful information about the dairy cow’s health status or about the management system efficiency. These data must also be easily available at low cost from milk recording organization. Recently, the MIR spectrometry offers the possibility to build routinely cheaper and more important databases. To develop management tools, milk samples have to be collected using comparable sampling methods. Unfortunately, in order to decrease the milk quality control costs, the International Committee for Animal Recording allows alternative sampling schemes including the collection of samples from morning or evening only milkings. This alternative sampling scheme can interact with phenotypic and genetic parameters. Therefore, additionally to the development of conversion equations, this thesis is establishing if morning or evening only milkings are genetically different traits. Last condition concerns a useful phenotypic and genetic variability. Milk FA profile is, among others, altered by genetics. So, one paper of this thesis concerns the setup of a useful genetic evaluation model able to estimate accurately the genetic part of milk fat composition variations. Routine genetic evaluation of production traits in dairy cattle commonly uses random regression model (RRM). Recently, “splines” have been advocated as a good alternative to Legendre polynomials (LP) for analyzing test-day yields in RRM. Therefore, several models are compared. Obtained results show the possibility to propose a practical and robust method for estimating accurate daily major FA production from single milking, useful for a further development of practical management tools helping dairy farmers in their daily decisions. [less ▲]

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See detailThe influence of background noise on vocal loading parameters in music theory teachers
Schiller, Isabel ULg; Morsomme, Dominique ULg; Sfez, Lou et al

Poster (2016, August 23)

Background: Music theory teachers, who teach rhythm, singing and other music-related skills and topics, depend greatly on a well-functioning voice. Unlike other schoolteachers, who primarily use their ... [more ▼]

Background: Music theory teachers, who teach rhythm, singing and other music-related skills and topics, depend greatly on a well-functioning voice. Unlike other schoolteachers, who primarily use their voice as a pedagogic tool, music theory teachers also use it as an instrument. Furthermore, they often engage in vocally demanding free-time activities requiring a singing voice. To date, few studies have specifically looked at the voice use of music theory teachers. This study aims (1) to measure the background noise level and the amount of vocal loading affecting this specific population, and (2) to describe the influence of background noise on vocal loading parameters. Methods: Thirteen French-speaking music theory teachers (9 females and 4 males) working in a music school were monitored for one workweek, using the VoxLog voice dosimeter (Sonvox). To investigate the professional and extra-professional environments, all subjects wore the dosimeter from early morning until the end of the day. The parameters analysed were background noise level, duration of phonation, sound pressure level (SPL) and fundamental frequency (F0) of voice. Results: Overall, the mean background noise level was 75.2 dB (SD=5.4). We measured higher background noise level at work (mean=78.2 dB, SD=5.8) than in the extra-professional environment (mean=72.2 dB, SD=5.2). As expected, a rise in background noise was accompanied by a significant rise in voice SPL in both males and females (r=.61, p<.001). A significant correlation between background noise and F0 was found in females (r=.41, p=.002), but not in males (r=.39, p=.055). Furthermore, our data exhibit a significant correlation between background noise and duration of phonation (r=.05, p<.001). Conclusion: Our data suggest, that in class, music theory teachers must cope with background noise levels that dramatically exceed the limit of 35 dB recommended by the WHO (Inserm, 2006). High background noise levels lead to an increase in voice SPL, a phenomenon known as the Lombard effect (Inserm, 2006). In female subjects, we also observed a rise in F0 further to high background noise. Like Ternström, Södersten, and Bohman’s (2002) study, our data indicate that high background noise levels increase the duration of phonation. In a noisy environment, subjects seem to prolong the voiced segments of speech to make themselves understood. In other words, high background noise levels result in higher vocal loading. In the long run, this may increase the risk of voice disorders such as hyperfunctional dysphonia or vocal fold pathologies consecutive to repeated microtrauma in music theory teachers. [less ▲]

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See detailANALYSE DE LA DEMANDE EN CHARBON DE BOIS PAR LES MÉNAGES URBAINS DE BUJUMBURA AU BURUNDI
Sabuhungu, Emery Gaspard ULg

Doctoral thesis (2016)

The objective of this study is to evaluate the demand for charcoal by urban households in Bujumbura in order to make recommendations ensuring the security of household energy and environmental protection ... [more ▼]

The objective of this study is to evaluate the demand for charcoal by urban households in Bujumbura in order to make recommendations ensuring the security of household energy and environmental protection. To achieve this objective, the analysis of the related documentation and collection of secondary data were carried out in order to formulate specific objectives, hypotheses and the methodology used in the course of this study. The specific objectives are: to analyze the structure, operation and market performance of the charcoal market in the city of Bujumbura and to compare this market to the cities of Lubumbashi and Kigali; to determine the charcoal consumption pattern by urban households in Bujumbura; to identify the factors which influence the demand for charcoal by urban households in Bujumbura; to evaluate the demand for charcoal by urban households in Bujumbura. The assumptions made in this study are: the charcoal market in the city of Bujumbura is a competitive and effective market; charcoal is the dominating cooking fuel used by urban households in Bujumbura and is consumed exclusively or in combination with others; an urban household’s demand for charcoal in Bujumbura is essentially based on household income, the size of household, eating habits (preparation of food that requires a long cooking time), the frequency of use of carbon and the possession or not of improved cooking stoves; the demand for charcoal by urban households in Bujumbura is high and this leads to significant annual deforestation. Three surveys were conducted to collect primary data. The first survey, with the specific objective of analysing the charcoal market in Bujumbura, was conducted among the key players of the charcoal value chain produced in the communes of Mugamba and Muramvya and consumed in the city of Bujumbura. The remaining two surveys, with the specific objective of analysing the consumption of charcoal by households, were conducted among households-users of charcoal of different standards of living in three areas of the city of Bujumbura (areas Buterere, Cibitoke and Rohero). The results indicate that the charcoal market is competitive. The production, the commercialisation and the consumption of charcoal allow the creation of positive value added all along the charcoal value chain. The use of cooking fuels by households in Bujumbura shows that they have not yet achieved an energy transition. In fact, 83% of those surveyed only use charcoal; 12% combine charcoal and electricity and 5% combine charcoal and firewood. The results revealed that the main factors influencing households demand for charcoal are: household income, the price of charcoal, household size, number of cooking sessions per day, frequency of preparation of cassava leaves and the possession or not of improved braziers. To solve the energy and environmental problem, a rehabilitation of woodland, an implementation of the best techniques of woodland planting with the most adaptable species on productive land, a greater penetration of substitutable energy to wood fuel such as gas or electricity, a growth in the use of improved cooking stoves in households and greater efficiency in wood carbonisation will help reduce the number of hectares of deforestation for wood energy needs. [less ▲]

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See detailOne pot synthesis by plasma treatment of Pt-based catalysts for PEM fuel cells
Busby, Yan; Gulas, Michal; Laurent-Brocq, Mathilde et al

Conference (2016, August 22)

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See detailAbility of Tuta absoluta (Lepidoptera: Gelechiidae) to develop on alternative host plant species
Bawin, Thomas ULg; Dujeu, David; De Backer, Lara ULg et al

in Canadian Entomologist (2016), 148(4), 434-442

The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous crops. The characterization of its host ... [more ▼]

The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous crops. The characterization of its host range could help to understand and prevent the dispersion behavior of the insect in the environment. In this study, the ability of T. absoluta to develop on 12 cultivated or non-cultivated plants including Solanaceae, Chenopodiaceae, Convolvulaceae, Fabaceae and Malvaceae species under laboratory conditions was assessed. For each plant species, we monitored the development times of immature stages, survival, sex ratios and adult fecundity rates. All the 6 tested non-solanaceous plants, including Chenopodium, Convolvulus and Malva species, were not able to sustain (i.e. allow growth and development) T. absoluta larvae. Among Solanaceae, Solanum species were the most suitable host plants for the pest, but others could be opportunistically colonized with fewer incidences. T. absoluta appears to be strongly related to solanaceous plants which would predominantly support self-sustaining field populations. Preventing crop infestation by removing potential host plants in the immediate field vicinity and culture rotations with non-solanaceous crops is of primary importance. [less ▲]

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See detailAggiornamento historiographique sur Godefroid Kurth (XIXème siècle-2016)
Genin, Vincent ULg

Conference (2016, August 19)

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See detailAspects fonciers de l'exil des religieux français en Belgique (1901-1914)
Murez, Jean-Baptiste ULg

Conference (2016, August 19)

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See detailLes enquêtes de terrain du Musée de la Vie wallonne : Un outil au service de la collecte de la mémoire, des savoirs et savoir-faire régionaux
Postula, Jean-Louis ULg

Conference (2016, August 19)

Débutées dans les années 1920, la réalisation de reportages sur le terrain puis la diffusion régulière des résultats de ces recherches ont été pendant longtemps l’un des traits distinctifs de la fonction ... [more ▼]

Débutées dans les années 1920, la réalisation de reportages sur le terrain puis la diffusion régulière des résultats de ces recherches ont été pendant longtemps l’un des traits distinctifs de la fonction scientifique mise en œuvre au Musée de la Vie wallonne. Jusqu’à la fin des années 1980 environ, les activités du Service des enquêtes ont permis au Musée de devenir le conservatoire d’une collection unique en son genre de documents d’archives multimédia – photographies, films et sons. La rénovation du Musée à partir de 2004, assortie de la réorientation de son projet muséal vers le modèle du « musée de société », a été l’occasion d’investir à nouveau du temps et des moyens dans la relance de cette riche tradition d’enquêtes ethnographiques. Grâce à de nombreux exemples, cette communication ambitionne de montrer l’évolution des terrains d’enquêtes du Musée, qui privilégie désormais l’exploration de nouvelles thématiques liées aux enjeux contemporains de nos sociétés urbaines, industrielles et post-industrielles. Oscillant entre continuité et renouvellement, les enquêtes du Musée de la Vie wallonne permettent à l’institution de se profiler comme un contributeur influent à la préservation du patrimoine culturel immatériel de notre région. [less ▲]

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See detailModel Sensitivity Studies of the Decrease in Atmospheric Carbon Tetrachloride
Chipperfield, M. P.; Liang, Q.; Rigby, M. et al

in Atmospheric Chemistry & Physics Discussions (2016), 2016

Carbon tetrachloride is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this ... [more ▼]

Carbon tetrachloride is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl4 is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (76% of total) but a reported 10% uncertainty in its combined photolysis cross-section and quantum yield has only a modest impact on the modelled rate of CCl4 decay. This is partly due to the limiting effect of the rate of transport of CCl4 from the main tropospheric reservoir to the stratosphere where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9% of total) is also relatively small. In contrast, the model shows that uncertainty in ocean loss (15% of total) has the largest impact on modelled CCl4 decay due to its sizeable contribution to CCl4 loss and large uncertainty range (157 to 313 years). With an assumed CCl4 emission rate of 39 Gg/yr, the reference simulation with best estimate of loss processes still underestimates the observed CCl4 (overestimates the decay) over the past two decades but to a smaller extent than previous studies. Changes to the rate of CCl4 loss processes, in line with known uncertainties, could bring the model into agreement with in situ surface and remote-sensing measurements, as could an increase in emissions to around 45 Gg/yr. Further progress in constraining the CCl4 budget is partly limited by systematic biases between observational datasets. For example, surface observations from the NOAA network are larger than from the AGAGE network but have shown a steeper decreasing trend over the past two decades. These differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl4 sinks. [less ▲]

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See detailIncorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages
Janssens, Julie; Meiners, Klaus M.; Tison, Jean-Louis et al

in Elementa: Science of the Anthropocene (2016), 4(1), 000123

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for ... [more ▼]

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for oceanic waters of the Southern Ocean has been clearly established, the processes leading to the enrichment of Fe in sea ice have yet to be investigated and quantified. We conducted two in situ sea-ice growth experiments during a winter cruise in the Weddell Sea. Our aim was to improve the understanding of the processes responsible for the accumulation of dissolved Fe (DFe) and particulate Fe (PFe) in sea ice, and of particulate organic carbon and nitrogen, dissolved organic carbon, extracellular polymeric substances, inorganic macro-nutrients (silicic acid, nitrate and nitrite, phosphate and ammonium), chlorophyll a and bacteria. Enrichment indices, calculated for natural young ice and ice newly formed in situ, indicate that during Antarctic winter all of the measured forms of particulate matter were enriched in sea ice compared to underlying seawater, and that enrichment started from the initial stages of sea-ice formation. Some dissolved material (DFe and ammonium) was also enriched in the ice but at lower enrichment indices than the particulate phase, suggesting that size is a key factor for the incorporation of impurities in sea ice. Low chlorophyll a concentrations and the fit of the macro-nutrients (with the exception of ammonium) with their theoretical dilution lines indicated low biological activity in the ice. From these and additional results we conclude that physical processes are the dominant mechanisms leading to the enrichment of DFe, PFe, organic matter and bacteria in young sea ice, and that PFe and DFe are decoupled during sea-ice formation. Our study thus provides unique quantitative insight into the initial incorporation of impurities, in particular DFe and PFe, into Antarctic sea ice. [less ▲]

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See detailReformulations of nonlinear binary optimization problems
Crama, Yves ULg

Scientific conference (2016, August 17)

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See detailThe Chemistry of New Garlic-Derived Organosulfur Compounds and the Molecular Basis of Olfaction »
Dethier, Bérénice ULg

Doctoral thesis (2016)

Garlic is a very popular condiment that has been used around the world for centuries. It is also a source of a remarkably extensive range of organosulfur compounds, whose chemistry is the focus of this ... [more ▼]

Garlic is a very popular condiment that has been used around the world for centuries. It is also a source of a remarkably extensive range of organosulfur compounds, whose chemistry is the focus of this thesis. The central reaction in formation of these compounds is the enzymatic cleavage of alk(en)yl cysteine sulfoxides by alliinases, which leads to sulfenic acids. The latter can then undergo condensation and rearrangement into various organosulfur compounds. Three aspects of the chemistry of garlic have been investigated in this thesis. First, little studied, minor organosulfur compounds in extracts of freshly chopped garlic were studied. These higher molecular weight compounds (MW 150–550) can be conveniently studied using state-of-the-art Liquid Chromatography-Mass Spectrometry (LC-MS) and Direct Analysis in Real Time-Mass Spectrometry (DART-MS) techniques. Novel garlic-derived compounds were studied and the structure of one representative compound containing a five-membered thiolane ring, ajothiolane, was determined by spectroscopic methods, using synthetic analogues as spectroscopic standards. The fate of compounds in a garlic extract over time was also studied, since the new, higher mass sulfur compounds are slowly formed by rearrangement of smaller metabolites a few days after maceration of the garlic. A second part of this thesis provides hands-on methods for the analysis and preparation of key garlic metabolites. The isolation and/or synthesis of alliin, alliinase and vinyldithiins have been optimized, and are proposed as turnkey procedures for future work. Finally, in an effort to explain the unique odor of garlic-related thiols and sulfides (in garlic breath, sweat, etc.), the interactions between odorants and olfactory receptors have been studied. Work described in this thesis contributed to this larger project by designing and synthesizing model macrocyclic odorants to resolve the mechanism of olfaction at the receptor level. The conclusions, arguing against the plausibility of the so-called “vibration theory of olfaction”, have been published as a foundation for future work on olfactory detection of thiols and other sulfur-containing compounds. [less ▲]

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