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See detailGas Sensing with Au-Decorated Carbon Nanotubes
Zanolli, Zeila ULg; Leghrib, Radouane; Felten, Alexandre et al

in ACS Nano (2011), 5(6), 4592-4599

The sensing properties of carbon nanotubes (CNTs) decorated with gold nanopar- ticles have been investigated by means of combined theoretical and experimental approaches. On one hand, first-principles and ... [more ▼]

The sensing properties of carbon nanotubes (CNTs) decorated with gold nanopar- ticles have been investigated by means of combined theoretical and experimental approaches. On one hand, first-principles and nonequilibrium Green's functions techniques give access to the microscopic features of the sensing mechanisms in individual nanotubes, such as electronic charge transfers and quantum conductances. On the other hand, drop coating deposition of carbon nanotubes decorated with gold nanoparticles onto sensor substrates and their characterization in the detection of pollutants such as NO2, CO, and C6H6 provide insight into the sensing ability of nanotube mats. Using the present combined approaches, the improvement in the detection of some specific gases (NO2 and CO) using Au-functionalized nanotubes is explained. However, for other gases such as C6H6, the Au nanoparticles do not seem to play a crucial role in the sensing process when compared with pristine CNTs functionalized with oxygen plasma. Indeed, these different situations can be explained by identifying the relationship between the change of resistance (macroscopic feature) and the shift of the Fermi level (microscopic feature) after gas adsorption. The understanding of the sensing ability at the atomic level opens the way to design new gas sensors and to tune their selectivity by predicting the nature of the metal that is the most appropriate to detect specific molecular species. [less ▲]

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See detailGas sensor array applied to the monitoring of biogas process
Adam, Gilles ULg; Lemaigre, Sébastien; Romain, Anne-Claude ULg et al

Conference (2011, May)

There is a lack of simple online monitoring system to control the performances of biogas reactors. The electronic nose technology appears to be an adapted device to deliver fast information about process ... [more ▼]

There is a lack of simple online monitoring system to control the performances of biogas reactors. The electronic nose technology appears to be an adapted device to deliver fast information about process disturbances in anaerobic reactors as it is adequate for online monitoring. In this study, twelve anaerobic mini-reactors were supervised with a home-made e-nose to observe process reaction in relation to organic overloads events. Usually, to avoid overload situations, on farms reactors are not fed at maximum load capacity, resulting in non optimized biogas production. The objective of the experiment was to determine if the gas sensors array feature can be related to the process state and if an indirect state variable, giving early warning of process faults, can be derived from the e-nose response. <br />The results demonstrated that focusing on gas phase of anaerobic reactors with a simple device composed of an array of non-specific gas sensors helped in the warning of disorders of the anaerobic digestion process. Mahalanobis distance from a cautious feeding group (group of observations indicating a good process) can be used as an indirect variable to evaluate the intensity of the state disorder. Euclidean distance has been also calculated but it was less informative than the Mahalanobis distance. [less ▲]

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See detailGas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames)
Borges, Alberto ULg; Delille, Bruno ULg; Schiettecatte, L. S. et al

Poster (2003, April)

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See detailGas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames)
Borges, Alberto ULg; Delille, Bruno ULg; Schiettecatte, Laure-Sophie et al

in Limnology & Oceanography (2004), 49(5), 1630-1641

We measured the flux of CO2 across the air–water interface using the floating chamber method in three European estuaries with contrasting physical characteristics (Randers Fjord, Scheldt, and Thames). We ... [more ▼]

We measured the flux of CO2 across the air–water interface using the floating chamber method in three European estuaries with contrasting physical characteristics (Randers Fjord, Scheldt, and Thames). We computed the gas transfer velocity of CO2 (k) from the CO2 flux and concomitant measurements of the air–water gradient of the partial pressure of CO2 (pCO2). There was a significant linear relationship between k and wind speed for each of the three estuaries. The differences of the y-intercept and the slope between the three sites are related to differences in the contribution of tidal currents to water turbulence at the interface and fetch limitation. The contribution to k from turbulence generated by tidal currents is negligible in microtidal estuaries such as Randers Fjord but is substantial, at low to moderate wind speeds, in macrotidal estuaries such as the Scheldt and the Thames. Our results clearly show that in estuaries a simple parameterization of k as a function of wind speed is site specific and strongly suggest that the y-intercept of the linear relationship is mostly influenced by the contribution of tidal currents, whereas the slope is influenced by fetch limitation. This implies that substantial errors in flux computations are incurred if generic relationships of the gas transfer velocity as a function of wind speed are employed in estuarine environments for the purpose of biogas air–water flux budgets and ecosystem metabolic studies. [less ▲]

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See detailGas Transfer Velocity as a critical variable in coastal ecosystem metabolism studies
Gazeau, F.; Gattuso, J.–P.; Frankignoulle, M. et al

Poster (2005, May)

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See detailGas-dynamic description of electrostatic solitons
Verheest, F.; Cattaert, Tom ULg; Lakhina, G. S. et al

in Journal of Plasma Physics (2004), 70

The nonlinear propagation of electrostatic solitary structures in unmagnetized multispecies plasmas is studied in the wave frame, where they are stationary, via the recently developed McKenzie approach as ... [more ▼]

The nonlinear propagation of electrostatic solitary structures in unmagnetized multispecies plasmas is studied in the wave frame, where they are stationary, via the recently developed McKenzie approach as an alternative to the more usual Sagdeev pseudo-potential method. This way of looking at the problem brings out the gas-dynamic aspects, which then allow a straightforward characterization of the solitary wave possibilities in terms of the species' own sonic points and of the global charge neutral points. A qualitative discussion of ion-, dust- and electron-acoustic solitary waves is given in terms of these concepts and the results are contrasted with those obtained by other methods. Ion-acoustic solitons can be shown to always be compressive, without invoking simplifying assumptions such as cold ions or Boltzmann electrons. Beam-plasmas can also be studied, as in the elect non-acoustic solitary wave model for the spiky structures of the broadband electrostatic noise observed in the auroral regions of the Earth's magnetosphere. Such solitons always show a potential dip. [less ▲]

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See detailGas-liquid mass transfer in a circulating jet-loop nitrifying MBR
Kouakou, Edouard; Salmon, Thierry ULg; Toye, Dominique ULg et al

in Chemical Engineering Science (2005), 60(22 Sp. Iss. SI), 6346-6353

Based on airlift configuration, a novel circulating jet-loop submerged membrane bioreactor (JLMBR) adapted to ammonium partial oxidation has been developed. Membrane technology and combined air and water ... [more ▼]

Based on airlift configuration, a novel circulating jet-loop submerged membrane bioreactor (JLMBR) adapted to ammonium partial oxidation has been developed. Membrane technology and combined air and water forced circulation are adopted to obtain a high biomass retention time and to achieve a separate control of mixing and aeration. This study is intended to determine how gas-liquid mass transfer is affected by operating conditions. In a first approximation, liquid was assumed to be perfectly mixed. A classical non-steady state clean water test, known as the "gas out-gas in" method, was used to determine the gas-liquid mass transfer coefficient k(L)a. Air and recirculated liquid superficial velocities were gradually increased from 0.013 to 0.019m s(-1) and 0.0056 to 0.011 m s(-1), respectively. Subsequently, the gas-liquid mass transfer coefficient kLa varied from 0.01 to 0.02 s(-1). It appears to be influenced by the combined action of air and recirculated liquid flowrates in the range 0.72-1.03N m(3) h(-1) and 0.30-0.58 m(3) h(-1), respectively, for air and liquid. Correlations are proposed to describe this double influence. Experiments were performed on tap water and a culture medium used for the autotrophic growth of nitrifying bacteria, respectively. Oxygen transfer appeared to be not significantly affected by the mineral salt (0.48 g 1(-1)) encountered in this medium. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailGas-liquid-solid bubble column investigation by electrical resistance tomography
Marchot, Pierre ULg; Fransolet, Emmanuelle; Crine, Michel ULg et al

Conference (2002)

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See detailGaseous and traditional forms of cryotherapy provide similar outcomes following TKA
Demoulin, Christophe ULg; Brouwers, M.; Darot, S. et al

in Orthoevidence: ACE-Evidence report (2013)

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See detailGaseous emissions associated to a high-fibre diet fed to gestating sows group-housed on deep litter
Philippe, François-Xavier ULg; Canart, B.; Laitat, Martine ULg et al

in Proceeding of the XIV ISAH Congress (2009)

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See detailGaseous emissions during the fattening of pigs kept either on fully slatted floor or on straw flow
Philippe, François-Xavier ULg; Laitat, Martine ULg; Canart, Bernard et al

in Animal (2007), 1(1), 1515-1523

The aim of this study was to compare the environmental impact of the straw-flow system for fattening pigs with the slatted-floor system by measuring pollutant gas emissions such as ammonia (NH3), nitrous ... [more ▼]

The aim of this study was to compare the environmental impact of the straw-flow system for fattening pigs with the slatted-floor system by measuring pollutant gas emissions such as ammonia (NH3), nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2), manure nitrogen (N) content and emissions of water vapour (H2O). Three successive batches of 32 pigs were fattened. For each batch, pigs were allotted to two groups raised in separated rooms fitted either with a concrete totally slatted-floor system (0.75 m(2) per pig) or with a straw-flow system (0.79 m(2) per pig). With this last system, pigs were kept on a sloped floor, straw being provided daily at the top of the pen. Throughout the fattening period, about 34.4 kg of straw were supplied per pig. The straw, mixed with dung, travelled down the slope by pig motion and went out of the pen to a scraped passage. The solid fraction was scraped every day, stored in a heap in the room and removed every month, 1 week before each period of gaseous emission measurement. The liquid fraction was automatically pumped from the scraped passage into a hermetic tank, which was emptied at the end of each fattening period. Rooms were ventilated mechanically in order to maintain a constant ambient temperature. Once a month, the emissions of NH3, N2O, CH4, CO2 and H2O were measured hourly for 6 consecutive days via infrared photoacoustic detection. Mean daily emissions per pig fattened on the slatted floor or on the sloped floor were, respectively, 4.98 and 13.31 g NH3, 0.67 and 0. 68 g N2O, 15.2 and 8.88 g CH4, 548 g and 406 g CO2 equivalents, 1.61 and 1.77 kg CO2 and 2.33 and 2.95 kg H2O. Except for N2O emissions, all the differences were statistically significant (P < 0.001). From the slatted-floor system, the amount of slurry removed per fattening period was on average 256 kg per pig. From the straw-flow system, solid manure amounted on average to 209 kg per pig and liquid manure to 53 kg per pig. The total N-content of the manure was 2.23 kg N per pig with the straw-flow system (solid and liquid manure) v. 3.26 kg N per pig for slurry from the slatted-floor system. This reduction of 30% observed with the sloped floor was mainly explained by the higher level of NH3-N emissions. [less ▲]

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See detailGaseous emissions from deep-litter pens with straw or sawdust for fattening pigs
Nicks, Baudouin ULg; Laitat, Martine ULg; Farnir, Frédéric ULg et al

in Animal Science (2004), 78(Part 1), 99-107

Three successive batches of fattening pigs were raised on a deep litter of straw in one room and of sawdust in another. The quantities of litter used per pig were 40 kg of straw and 81 kg of sawdust. Once ... [more ▼]

Three successive batches of fattening pigs were raised on a deep litter of straw in one room and of sawdust in another. The quantities of litter used per pig were 40 kg of straw and 81 kg of sawdust. Once a month, the emissions of ammonia, nitrous oxide, methane, carbon dioxide and water vapour were measured continuously for 6 days consecutively. Gaseous emissions from pig raising on sawdust-based litter and straw-based litter were respectively 12.16 and 13.61 g per pig per day for ammonia (NH3), 4.96 and 7.39 g per pig per day for methane (CH4), 2.09 and 0.03 g per pig per day for nitrous oxide (N2O), 3.15 and 2.74 kg per pig per day for water (H2O) and 1.32 and 1.30 kg per pig per day for carbon dioxide (CO2). Differences between the emissions of the two litters were significant for N2O and H2O (P < 0.01). The nitrogen content of the manures collected at the end of the experiment was 1.47 kg per pig for the straw-based litter and 1.07 kg per pig for that based on sawdust. Nitrogen emissions were calculated under the assumption that no gases volatilized from the litter or from the animals other than NH3 and N2O. With the two litters, about 50% of nitrogen excreted by the pigs was emitted into the atmosphere in the form of N-2. [less ▲]

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See detailGaseous emissions from fattening pigs offered an ad libitum high-fibre diet and kept on fully slatted floor: preliminary results
Philippe, François-Xavier ULg; Laitat, Martine ULg; Wavreille, José et al

in Proceedings of the International Symposium on Emissions of Gas and Dust from Livestock (2012)

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See detailGaseous emissions from fattening pigs offered an ad libitum high-fibre diet and kept on fully slatted floor: preliminary results
Philippe, François-Xavier ULg; Laitat, Martine ULg; wavreille, José et al

in Proceedings of the 2nd Scientific Meeting of the Faculty of Veterinary Medicine (Liège – Belgium) (2012)

According to the literature, the diet composition of livestock can influence polluting gas emissions from agriculture. The aim of this preliminary study was to measure gaseous emissions from fattening ... [more ▼]

According to the literature, the diet composition of livestock can influence polluting gas emissions from agriculture. The aim of this preliminary study was to measure gaseous emissions from fattening pigs offered an ad libitum high-fibre diet (HFD) and kept on fully slatted floor. A batch of 24 fattening pigs was divided into two homogeneous groups randomly allocated to a treatment: conventional cereals-based diet or sugar beet pulpbased diet (HFD). With HFD, a significant decrease of animal performance was observed (837 vs. 962 g for the average daily gain). With pigs offered HFD, gaseous emissions per pig were significantly lower for NH3 (-30%, 6.64 vs. 9.47 g/d; P<0.05) and significantly greater for CH4 (+40%, 6.46 vs. 4.60 g/d; P<0.05). The emissions of N2O (0.34 g/d), CO2equivalent (0.27 kg/d), CO2 (1.68 kg/d) were not significantly influenced by the diet. Due to a more important microbial activity with HFD, the lower NH3-emissions could be attributed to the shift of a part of excreted nitrogen from urine (as urea) to faeces (as protein form), and to a lower slurry pH explained by the increase of volatile fatty acid content. The higher CH4-emissions could be explained by a greater production in the digestive tract and in the slurry due to fibre fermentations. In conclusion, HFD allowed decreasing NH3- and increasing CH4-emissions. However, in terms of climate change, this increase was offset by the decrease of indirect N2O-emissions due to NH3-emission decrease, as indicated by the similar CO2equivalent-emissions in the two groups. [less ▲]

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See detailGaseous emissions from group-housed gestating sows kept on deep litter and offered an ad libitum high-fibre diet
Philippe, François-Xavier ULg; Canart, Bernard; Laitat, Martine ULg et al

in Agriculture, Ecosystems & Environment (2009), 132

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part in the global problem of ... [more ▼]

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part in the global problem of climate change. Ammonia (NH3) emissions are responsible of soil and water acidification and eutrophication and contribute also to indirect emissions of N2O. The objective of this study was to investigate the effects of a high-fibre diet offered ad libitum to gestating sows on gaseous emissions (NH3, N2O, CH4, CO2 and water vapour (H2O)). Four successive batches of 10 gestating sows were used for this trial. Each batch was divided into 2 homogeneous groups randomly allocated to a treatment: restricted conventional cereals based diet or high-fibre diet based on sugar beet pulp (42%). The groups were separately kept in two identical rooms equipped with a straw-bedded pen of 12.6 m². For restricted sows, meals were provided once a day in individual feeding stalls available only during the feeding time. In both rooms, ventilation was automatically adapted to maintain a constant ambient temperature. The gas emissions were measured by infrared photoacoustic detection during 6 consecutive days at the 6th, 9th and 12th weeks of gestation. Sows performance (body weight gain, backfat thickness, number and weight of piglets) was not significantly different according to the diet. With sows offered high-fibre diet and compared to sows offered restricted diet, gaseous emissions were significantly greater for NH3 (9.64 g NH3-N d-1 sow-1 vs. 5.37 g NH3-N d-1 sow-1; P < 0.001), CH4 (17.20 g d-1 sow-1 vs. 15.21 g d-1 sow-1; P < 0.01), CO2 (3.00 kg d-1 sow-1 vs. 2.41 kg d-1 sow-1; P < 0.001) and H2O (4.71 kg d-1 sow-1 vs. 3.68 kg d-1 sow-1; P < 0.001) and significantly lower for N2O (0.97 g N2O-N d-1 sow-1 vs. 2.48 g N2O-N d-1 sow-1; P < 0.001) and CO2 equivalents (0.88 kg d-1 sow-1 vs. 1.55 kg d-1 sow-1; P < 0.001). In conclusion, the effects of high-fibre diet offered to gestating sows on deep litter on environment seem ambiguous with an increase of NH3 emissions but a decrease of N2O and CO2 equivalent emissions. [less ▲]

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See detailGaseous emissions from weaned pigs raised on different floor systems
Cabaraux, Jean-François ULg; Philippe, François-Xavier ULg; Laitat, Martine ULg et al

in Agriculture, Ecosystems & Environment (2009), 130

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part to the global problem of ... [more ▼]

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part to the global problem of climate change. Ammonia (NH3) emissions are responsible of soil acidification and eutrophication and contribute also to indirect emissions of N2O. This work evaluated the influence of the type of floor on the emissions of these gases in the raising of weaned pigs. Two trials were carried out. In the first trial, the animals were kept either on fully slatted floor or on straw-based deep litter and, in the second one, either on fully slatted floor or on sawdust-based deep litter. For each trial and on each type of floor, 2 successive batches of weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. The rooms were automatically ventilated to maintain a constant ambient temperature. The performance of the animals was not significantly different according to the floor type. In trial 1, the nitrogen contents of the straw deep litter (including the substrate) and slurry were respectively 276 and 389 g pig-1. In trial 2, the sawdust deep litter and slurry nitrogen contents were respectively 122 and 318 g pig-1. Raising pigs on straw deep litter produced proportionately around 100% more NH3 than raising pigs on slatted floor (0.61 vs. 0.31 g NH3-N d-1 per pig; P<0.05). Differences in CO2, H2O and CH4 emissions were not significant between systems. Raising pigs on sawdust deep litter produced also proportionately more NH3 (+52%; 0.55 vs. 0.36 g NH3-N d-1 per pig; P<0.01) but also more CO2 (+25%; 427 vs. 341 g d-1 per pig; P<0.001) and H2O (+65%; 981 vs. 593 g d-1 per pig; P<0.001) and less CH4 (-40%; 0.52 vs. 0.86 g d-1 per pig; P<0.001) than raising pigs on slatted floor. Practically no N2O emission was observed from rooms with slatted floor while the N2O emissions were 0.03 and 0.32 g N2O-N d-1 per pig for the straw and sawdust deep litter respectively. The warming potential of the greenhouse gases (N2O + CH4), were about 22, 34 and 168 g CO2 equivalents per day and per pig on fully slatted floor, straw or sawdust deep litter respectively. In conclusion, pollutant gas emissions from rearing of weaned pig seem lower with fully slatted plastic floor system than with deep litter systems [less ▲]

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See detailGaseous emissions in the raising of fattening pigs on fully slatted floor or on straw-based deep litter
Nicks, Baudouin ULg; Philippe, François-Xavier ULg; Laitat, Martine ULg et al

in Proceedings of the XIIth international congress of the International Society for animal Hygiene, Animals and the environment (2005)

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See detailGaseous emissions in the raising of weaned pigs on fully slatted floor or on sawdust-based deep litter
Nicks, Baudouin ULg; Laitat, Martine ULg; Farnir, Frédéric ULg et al

in Proceedings of the International workshop on Green Pork Production (2005)

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See detailGaseous emissions in the raising of weaned pigs on fully slatted floor or on straw-bases deep litter
Nicks, Baudouin ULg; Laitat, Martine ULg; Farnir, Frédéric ULg et al

in Clement, G.; Madec, F. (Eds.) Proceedings of the in- between congress of the International Society for Animal Hygiene (2004)

Detailed reference viewed: 13 (7 ULg)