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See detailNitric oxide: a new messenger in the brain.
Bruhwyler, J.; Chleide, E.; Liégeois, Jean-François ULg et al

in Neuroscience & Biobehavioral Reviews (1993), 17(4), 373-84

The important role played by nitric oxide (NO) in the central nervous system has largely been emphasized in the recent literature. It can originate at least from four different sources: the endothelium of ... [more ▼]

The important role played by nitric oxide (NO) in the central nervous system has largely been emphasized in the recent literature. It can originate at least from four different sources: the endothelium of cerebral vessels, the immunostimulated microglia and astrocytes, the nonadrenergic noncholinergic nerve, and the glutamate neuron. NO has been implicated in a large number of pathologies (such as neurotoxicity in Alzheimer's disease and Huntington's disease, cerebral ischemia, stroke, and anxiety) and also in normal physiological functions (such as memory and learning, regulation of the cerebrovascular system, modulation of the wakefulness, mediation of nociception, olfaction, food intake and drinking, regulation of noradrenaline, and dopamine release). The aim of this paper is to review and to integrate the most recent advances in our understanding of the roles of NO in the brain. [less ▲]

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See detailNitric oxide: does it play a role in the heart of the critically ill?
MASSION, Paul ULg; Moniotte, S.; Balligand, J. L.

in Current Opinion in Critical Care (2001), 7(5), 323-36

Nitric oxide regulates many aspects of myocardial function, not only in the normal heart but also in ischemic and nonischemic heart failure, septic cardiomyopathy, cardiac allograft rejection, and ... [more ▼]

Nitric oxide regulates many aspects of myocardial function, not only in the normal heart but also in ischemic and nonischemic heart failure, septic cardiomyopathy, cardiac allograft rejection, and myocarditis. Accumulating evidence implicates the endogenous production of nitric oxide in the regulation of myocardial contractility, distensibility, heart rate, coronary vasodilation, myocardial oxygen consumption, mitochondrial respiration, and apoptosis. The effects of nitric oxide promote left ventricular mechanical efficiency, ie, appropriate matching between cardiac work and myocardial oxygen consumption. Most of these beneficial effects are attributed to the low physiologic concentrations generated by the constitutive endothelial or neuronal nitric oxide synthase. By contrast, inducible nitric oxide synthase generates larger concentrations of nitric oxide over longer periods of time, leading to mostly detrimental effects. In addition, the recently identified beta3-adrenoceptor mediates a negative inotropic effect through coupling to endothelial nitric oxide synthase and is overexpressed in heart failure. An imbalance between beta 1 and beta2-adrenoceptor and beta3-adrenoceptor, with a prevailing influence of beta3-adrenoceptor, may play a causal role in the pathogenesis of cardiac diseases such as terminal heart failure. Likewise, changes in the expression of endothelial nitric oxide synthase or inducible nitric oxide synthase within the myocardium may alter the delicate balance between the effects of nitric oxide produced by either of these isoforms. New treatments such as selective inducible nitric oxide synthase blockade, endothelial nitric oxide synthase promoting therapies, and selective beta3-adrenoceptor modulators may offer promising new therapeutic approaches to optimize the care of critically ill patients according to their stage and specific underlying disease process. [less ▲]

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See detailLa nitrification dans le cadre du traitement des eaux usées: production de nitrites, préservation des nitrifiants et effet d'un support
Malchair, Sandrine ULg

Master's dissertation (2002)

Le monde actuel est confronté à de nombreux problèmes environnementaux résultant des activités anthropiques. Parmi ceux-ci se pose le problème de la pollution de l’eau. Veiller au maintien de la qualité ... [more ▼]

Le monde actuel est confronté à de nombreux problèmes environnementaux résultant des activités anthropiques. Parmi ceux-ci se pose le problème de la pollution de l’eau. Veiller au maintien de la qualité de l’eau devient une nécessité pour les sociétés humaines. Ce mémoire s’inscrit dans le cadre du traitement des eaux usées. Nous avons étudié le processus de nitrification, qui associé à la dénitrification, permet de diminuer l’impact de la pollution par l’azote. Ce mémoire s’inscrit dans le cadre d’un projet de la région wallonne qui étudie l’élimination de la charge azotée des eaux usées d’origine agricole par dans une première phase, le développement d’un procédé biotechnologique permettant de produire préférentiellement des nitrites ; pour ensuite, éliminer ceux-ci par dénitrification. La nitrification peut être définie comme étant la transformation biologique de composés organiques et inorganiques (NH4+) d’une forme réduite en forme plus oxydée (NO2-, NO3-). Ce processus peut être le fait d’organismes autotrophes et hétérotrophes. La présence de nitrate dans les cours d’eau peut provoquer l’eutrophisation de ces systèmes aquatiques entraînant des conditions anoxiques et la diminution de la diversité. Ce mémoire est composé de trois chapitres traitant chacun un aspect de la nitrification dans le traitement des eaux usées. Le premier chapitre tente de déterminer les conditions du milieu favorisant les bactéries responsables de la nitritation. Pour cela, des systèmes d’étude en continu sont mis en place. Lors de cette expérience, il est apparu nécessaire de toujours disposer d’inocula stables. C’est pourquoi, dans le second chapitre, nous avons testé différentes méthodes de préservation des populations bactériennes. Le dernier chapitre de ce mémoire étudie l’effet de différents supports sur la nitrification. Dans le premier volet de ce mémoire, les systèmes de culture en continu ont permis d’établir les conditions du milieu favorables à la production de nitrites. Ces conditions sont les suivantes : Concentration en N-NH4+ de 300 mg N/l, pH de 8.2 ± 0.2, température de 30°C et concentration en oxygène dissous inférieure à 2mg/l. Les paramètres les plus importants pour favoriser les populations bactériennes oxydant l’ammonium sont le pH et la teneur en oxygène dissous. Nous avons mis en évidence que les fluctuations de pH sont néfastes pour le maintien de la nitritation. Les teneurs en oxygènes dissous faibles (inférieures à 2mg/l) stimulent les bactéries oxydant l’ammonium mais n’affectent pas celles qui oxydent les nitrites. Le second volet de ce mémoire étudie les méthodes de préservation de la population nitrifiante afin d’envisager la méthode de stockage adéquate permettant à ces populations de maintenir leur activité nitrifiante. Les différentes méthodes de conservation envisagées sont les suivantes : conservation à court terme à 4°C, conservation à plus long terme à -20°C, -80°C ou par lyophilisation, en présence ou en absence de cryoprotecteurs (DMSO et glycérol). Il apparaît que les traitements employés ont des effets significatifs sur les taux de production de nitrites plus nitrates (p<0.05). La lyophilisation ne semble pas être une technique adéquate pour la préservation des nitrifiants. L’emploi de DMSO comme cryoprotecteur semble plus adéquat que l’emploi de glycérol. La conservation à court terme à 4°C semble appropriée aux nitrifiants. A plus long terme, la conservation à -80°C en présence de DMSO semble la plus adéquate aux populations de bactéries nitrifiantes. Le dernier volet de ce mémoire envisage l’effet d’un support sur la nitrification. Notre hypothèse de départ était que la présence d’un support favorise la nitrification. Dans le sol, les bactéries se lient fortement aux argiles. Nous avons utilisé quatre argiles comme support dans cette expérience. Nous avons employé, également des cubes de mousses de polyuréthane (grande surface pour que les bactéries se fixent) et de la craie (tamponner le milieu). Les traitements envisagés n’ont aucun effet significatif sur la production de nitrites plus nitrates (p> 0.05). Notre hypothèse de départ a été infirmée. Cependant, aucune inhibition due à la présence du support sur la nitrification n’est observée. En conclusion, nous pouvons dire qu’il est possible en ajustant le pH et la teneur en oxygène dissous de favoriser les populations de bactéries oxydant l’ammoniac et donc la production de nitrites. Les conservations à court et à long terme de populations nitrifiantes sont envisageables. La présence de support a maintenu la nitrification à un taux identique à celui observé pour des populations témoins sans support. Malgré leurs propriétés respectives, aucun support testé n’a favorisé la nitrification. [less ▲]

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See detailNitroaldol condensation catalyzed by topologically modulable cooperative acid–base chitosan–TiO2 hybrid materials
Aqil, Abdelhafid ULg; El Kadib, Abdelkrim; Aqil, Mohamed ULg et al

in RSC Advances (2014), 4(63), 33360-33363

Chitosan–TiO2 shaped as macroporous aerogels, lamellar cryogels or electrospun films act synergistically as acid–base bifunctional catalysts. Depending on the topology of the material, a marked difference ... [more ▼]

Chitosan–TiO2 shaped as macroporous aerogels, lamellar cryogels or electrospun films act synergistically as acid–base bifunctional catalysts. Depending on the topology of the material, a marked difference in the selectivity for nitroaldol condensation is observed. [less ▲]

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See detailNitrogen Adsorption on Silica Xerogels or the Odd Look of a t Plot
Gommes, Cédric ULg; Blacher, Silvia ULg; Pirard, Jean-Paul ULg

in Langmuir (2005), 21

Nitrogen adsorption in some silica xerogels leads to t plots that cannot be interpreted by the occurrence of capillary condensation or by the filling of micropores. Their particular appearance stems from ... [more ▼]

Nitrogen adsorption in some silica xerogels leads to t plots that cannot be interpreted by the occurrence of capillary condensation or by the filling of micropores. Their particular appearance stems from the unique columnar structure of these samples at the nanometer scale, by which the adsorbent surface has a positive curvature. A standard thermodynamic approach allows the phenomenon to be exploited to characterize the samples. [less ▲]

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See detailNitrogen and carbon cycling in the North Sea and exchange with the North Atlantic-A model study, Part II: Carbon budget and fluxes
Kuhn, Wilfried; Paetsch, Johannes; Thomas, Helmuth et al

in Continental Shelf Research (2010), 30(16), 1701-1716

The 3-d coupled physical-biogeochemical model ECOHAM (version 3) was applied to the Northwest-European Shelf (47 degrees 41'-63 degrees 53'N, 15 degrees 5'W-13 degrees 55'E) for the years 1993-1996 ... [more ▼]

The 3-d coupled physical-biogeochemical model ECOHAM (version 3) was applied to the Northwest-European Shelf (47 degrees 41'-63 degrees 53'N, 15 degrees 5'W-13 degrees 55'E) for the years 1993-1996. Carbon fluxes were calculated for the years 1995 and 1996 for the inner shelf region, the North Sea (511,725 km(2)). This period was chosen because it corresponds to a shift from a very high winter-time North Atlantic Oscillation Index (NAOI) in 1994/1995, to an extremely low one in 1995/1996, with consequences for the North Sea physics and biogeochemistry. During the first half of 1996, the observed mean SST was about 1 degrees C lower than in 1995; in the southern part of the North Sea the difference was even larger (up to 3 degrees C). Due to a different wind regime, the normally prevailing anti-clockwise circulation, as found in winter 1995, was replaced by more complicated circulation patterns in winter 1996. Decreased precipitation over the drainage area of the continental rivers led to a reduction in the total (inorganic and organic) riverine carbon load to the North Sea from 476 Gmol C yr(-1) in 1995 to 340 Gmol C yr(-1) in 1996. In addition, the North Sea took up 503 Gmol C yr(-1) of CO2 from the atmosphere. According to our calculations, the North Sea was a sink for atmospheric CO2, at a rate of 0.98 mol C m(-2) yr(-1), for both years. The North Sea is divided into two sub-systems: the shallow southern North Sea (SNS; 190,765 km(2)) and the deeper northern North Sea (NNS; 320,960 km2). According to our findings the SNS is a net-autotrophic system (net ecosystem production NEP > 0) but released CO2 to the atmosphere: 159 Gmol C yr(-1) in 1995 and 59 Gmol C yr(-1) in 1996. There, the temperature-driven release of CO2 outcompetes the biological CO2 drawdown. In the NNS, where respiratory processes prevail (NEP < 0), 662 and 562 Gmol C yr(-1) were taken up from the atmosphere in 1995 and 1996. respectively. Stratification separates the productive, upper layer from the deeper layers of the water column where respiration/remineralization takes place. Duration and stability of the stratification are determined by the meteorological conditions, in relation to the NAO. Our results suggest that this mechanism controlling the nutrient supply to the upper layer in the northern and central North Sea has a larger impact on the carbon fluxes than changes in lateral transport due to NAOI variations. The North Sea as a whole imports organic carbon and exports inorganic carbon across the outer boundaries, and was found to be net-heterotrophic, more markedly in 1996 than in 1995. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲]

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See detailNitrogen balance and nitrate residues in pastures grazed by dairy cows and and fertilised with mineral fertiliser, pig slurry or cattle compost
Dufrasne, Isabelle ULg; Meura, S.; Cabaraux, Jean-François ULg et al

in Permanent and temporary grassland plant, environment and economy, A De Vliegher an L. Carlier editors, Book of abstracts of 14th Symposium of European Grassland Federation (2007)

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See detailNitrogen balance and nitrate residues in pastures grazed by dairy cows and fertilised with mineral fertiliser, pig slurry or cattle compost
Dufrasne, Isabelle ULg; Meura, Stéphane; Cabaraux, Jean-François ULg et al

in Permanent and temporary grassland plant, environment and economy; A. De Vliegher and L. Carlier (Eds); Proceedings of 14th symposium of the European Grassland Federation (2007)

A code of good practices was established by each European member state according to the nitrate directive. In Belgium, the nitrogen (N) inputs from slurry or compost are limited to 230 kg N/ha in pastures ... [more ▼]

A code of good practices was established by each European member state according to the nitrate directive. In Belgium, the nitrogen (N) inputs from slurry or compost are limited to 230 kg N/ha in pastures. Larger amounts can be applied when a program of additional measurements, including soil nitrates analysis, is followed by the farmer. This trial aims to measure nitrogen balance and soil nitrates in pastures fertilised with mineral nitrogen fertiliser (min N), pig slurry (S) or cattle compost (C). The pastures were grazed by dairy cows and the fertilisation allowed similar efficient N levels. N inputs by fertilisation were different at 169, 170 and 102 kg N/ha in C, S and min N plots respectively. The use of pig slurry and cattle compost as compared with mineral N fertiliser increased N balance and reduced apparent N efficiency. The nitrogen, potassium and phosphorus nutrition indexes, the number of grazing days and the milk yields per ha were not different. The soil nitrate contents were not increased by use of slurry or compost. The overall low nitrate contents suggested a low nitrate leaching with the three types of fertilisation. [less ▲]

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See detailNitrogen budget of the northwestern Black Sea shelf inferred from modeling studies and in situ benthic measurements
Grégoire, Marilaure ULg; Friedrich, Jana

in Marine Ecology. Progress Series (2004), 270

A 3D eddy-resolving coupled biogeochemical-hydrodynamical model and in situ observations are used to investigate benthic processes on the Black Sea's NW shelf. Measurements of benthic fluxes (oxygen ... [more ▼]

A 3D eddy-resolving coupled biogeochemical-hydrodynamical model and in situ observations are used to investigate benthic processes on the Black Sea's NW shelf. Measurements of benthic fluxes (oxygen, nutrients, redox compounds) with in situ flux chambers are analyzed in regard to sediment dynamics on the shelf. The seasonal/interannual and spatial variability of benthic processes is explained in terms of 3D ecohydrodynamics. The space/time distribution of benthic fluxes depended on the position of the river plume and the associated primary production, intensity of vertical mixing and water depth. Model results and in situ observations reveal the presence of a region of intense benthic recycling and high benthic nutrient fluxes nearshore and in the northern part of the shelf. The model estimates that this region covers about 15 % of the shelf area and is connected to the high productivity and high sedimentation caused by river input of organic matter. On the offshore shelf, covering about 85 % of the shelf area, benthic nutrient regeneration is low due to low productivity. Benthic mineralization pathways (aerobic respiration, denitrification, sulfate reduction, methanogenesis) are quantified. In the high flux region, more than 55 % and in the offshore low flux region more than 80 % of the organic matter is decomposed by aerobic respiration. In the high flux region, sulfate reduction is the main anaerobic pathway, whereas denitrification is more important on the low flux offshore shelf. At the shelf edge, under the influence of anoxic waters, more than 60 % of organic matter is remineralized by sulfate reduction. Little organic matter is decomposed by methanogenesis. A mass balance of particulate organic carbon (POC) and particulate organic nitrogen (PON), integrated over the whole shelf and year, shows that 3.7 to 4.2 x 10(6) t of POC reach the sediments, while model results give a value of 1.4 x 10(6) t C. The annual ammonium benthic outflux is estimated at 85 x 10(3) and 174 x 10(3) t N by in situ data and the model, respectively. The amount of nitrogen lost by burial and denitrification estimated from in situ observations is 57 x 10(3) and 324 x 10(3) t N, respectively. Therefore, NW shelf Black Sea sediments are an efficient sink for riverine nitrogen, trapping about 50 % of the annual river discharge in total inorganic N. [less ▲]

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See detailNitrogen budget on the shelf and slope area of the Back Sabasin as inferred from modeling experiments
Grégoire, Marilaure ULg; Beckers, Jean-Marie ULg; Friederich, J. et al

in Second International Conference on "Oceanography of the Eastern Mediterranean and Black Sea: Similarities and Differences of Two Interconnected Basins" (2002)

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See detailNitrogen deposition and nitrification in coniferous forests’
Carnol, Monique ULg

Doctoral thesis (1997)

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forest ecosystems. High anthropogenic N emissions, mainly from fossil fuel combustion and ... [more ▼]

The increased inorganic nitrogen (N) deposition in the last decades has become a major concern for the health of forest ecosystems. High anthropogenic N emissions, mainly from fossil fuel combustion and livestock agriculture, have resulted in both high gaseous concentrations and high deposition in rainfall and throughfall. In forest ecosystem, where N is no longer limiting to primary production due to high inputs, the excess N is thought to be related to forest decline and a concept of ‘N saturation ‘ has been developed. In particular, N in the form of NH4, in excess to plant and microbial demands could lead to soil acidification if nitrified in the soil and leached, causing loss of base cations or mobilisation of phytotoxic aluminium. Nutrient imbalances due to high soil solution NH4/cation ratios or damaged root systems may also occur. The fate of the incoming NH4 is central to determining the effects on the ecosystem, and is closely related to the controls of nitrification. Although this process has been intensely studied in pure cultures for some nitrifying bacteria, the organisms responsible and controlling factors in acid forest soils are still poorly understood. A better comprehension of the fate of NH4 deposition is necessary to determine ‘Critical Loads for N’, the threshold deposition not damaging to the ecosystem, which is used as a political tool for quantifying pollution limits. In this thesis, I focused on a) the effects of increased (NH4)2SO4 deposition on soil solution chemistry of six coniferous forest sites the presence of live roots, b) the impacts of (NH4)2SO4 deposition on Norway spruce (Picea abies [L.] Karst) and Scots pine (Pinus sylvestris L.) fine roots, and c) the controls of nitrification in an acid forest soil. The work was part of the CEC project ‘CORE’, investigating the effects of atmospheric pollution on nutrient turnover in soils. An identical field experiment was performed in six coniferous sites, situated in five European countries. Chronically increased NH4 deposition by 75 kg N ha-1 a-1 through (NH4)2SO4 application, demonstrated the contrasting responses of the different ecosystems. Soil solution concentrations and yearly ionic fluxes were analysed. (NH4)2SO4 treatment resulted in deposition of 79 to 93 kg N ha-1 a-1 at the different sites. In the two less acidic, clay/clay loam soils, only 6% of the added NH4 was lost through leaching. The two sandy soils lost up to 75% of the added NH4, and the two remaining sites lost ca. 25%. Leaching of added NH4 was thought to be related to soil physico-chemical characteristics, such as pH, C and N content and texture. NO3 leaching was increased at three sites, only 4-9 months after starting the (NH4)2SO4 treatment, with a maximum doubling of concentrations. One sandy soil failed to nitrify under any condition, and the other sandy soil showed high NO3 leaching under all treatments, but no increase due to increased N inputs. The presence of live roots reduced NO3 leaching in two sites, delaying the increase in soil solution NO3 concentrations in response to the (NH4)2SO4 deposition in one of them. In all nitrifying soils, soil solution NO3 concentrations were related to cation concentrations, with Al being the dominant cation in the more acid soils with low base saturation. This experiment demonstrated the importance of soil N storage capacity and nitrification potential in determining the consequences of increased NH4 deposition, and the strong relationship between NO3 and cation leaching. Ionic fluxes and soil solution chemistry were further analysed in one of the six sites (Grizedale, UK). In this Norway spruce stand on clay soil, NO3 fluxes were increased by increased (NH4)2SO4 deposition, and mainly balanced by increased Al losses. This soil had a pHH2O around 3.6, and was characterised by over 90% of the exchange complex being occupied by Al. Independent of treatment, soil solution changed from Ca to Al leaching during the 18 month field experiment, with a decrease in soil solution pH from 4.9 to 3.8. At the end of the experiment, soil solution Al concentrations were higher for the (NH4)2SO4 treatments. It was suggested that nitrification had caused the pH decrease, with a further lowering of the base saturation, linked to a abrupt increase in soil solution Al concentrations. The impacts of increased (NH4)2SO4 deposition and soil characteristics on Norway spruce root biomass and vitality, and on Norway spruce and Scots pine fine root chemistry, were investigated with an ingrowth core technique. The same experiment was performed in a Norway spruce stand on clay soil (Grizedale, UK) and a Scots pine stand on sandy soil (Wekerom, NL), using soil from each of the two sites. For Norway spruce, root biomass and numbers of fine root tips were higher in the organic than in the mineral horizon of the clay and sandy soils. This was related to higher fine root Al and lower Ca contents in the mineral horizon. Root biomass and the proportion of dead roots were higher in the clay soil, compared to the sandy soil, with higher root Al contents, despite lower soil solution Al concentrations than in the sandy soil. For Norway spruce, a negative correlation between root biomass and fine root Al content was established. Enhanced N deposition caused an increase in the total number of root tips and in the proportion of dead roots in the sandy soil. Effects of increased (NH4)2SO4 deposition on root biomass were not significant for the clay soil, yet caused increased fine root N content in the organic horizon for both species. Scots pine fine roots also showed higher Al and lower Ca contents in the mineral horizon. (NH4)2SO4 treatment caused increased fine root Al content and a decreased Mg/Al ratio in the mineral layer of the sandy soil, with opposite effects in the clay soil. This (NH4)2SO4 treatment effect in the sandy soil for Scots pine was the only indication of a potential adverse effect of (NH4)2SO4 deposition on fine roots. Results demonstrated the dominant importance of inherent soil characteristics and the stratification into soil horizons on fine root growth and chemical composition. The effects of temperature, throughfall volume and NH4 deposition on soil solution NO3 concentrations, N2O emissions and numbers of NH4 oxidisers were investigated for the Grizedale soil in a controlled laboratory experiment. Multiple regression and surface response analysis revealed temperature as the most important factor, with an optimum for NO3 leaching and numbers of NH4 oxidisers in the mineral horizon at 11°C. Volume acted independently of temperature with a minimum at 870 mm throughfall 2 weeks-1. The relatively low optimum temperature compared to other studies was explained by the minimum disturbance of the soil in the current study. NO3 fluxes increased quadratically with throughfall volume. N2O fluxes increased quadratically with temperature and throughfall volume, and showed high variability. It was suggested that the temperature optimum for net nitrification depended on the physico-chemical characteristics of the soil and on the activity of decomposers, by competition for O2 and NH4. Optimum temperatures may have been overestimated in previous studies using disturbed soils. The regression model for NO3 leaching derived from the laboratory experiment was applied to data from the previous field experiment and tested with different time intervals for temperature input parameters. A model including two-monthly mean temperatures yielded the best fit between measured and simulated values, as determined by correlation and minimum sum of squared residuals. Simulated NO3 leaching was over-estimated in the second part of the field study. The good correspondence between field temperature frequency distribution and the optimum temperature determined by the regression model, as well as the high correlation between measured and simulated values, demonstrated the adequacy of a quadratic model with a relatively low temperature optimum to describe field NO3 leaching, determined for the same soil with an identical sampling design. [less ▲]

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See detailNitrogen dynamics in Posidonia oceanica cuttings: implications for transplantation experiments
Lepoint, Gilles ULg; Vangeluwe, Denis; Eisinger, Michael et al

in Marine Pollution Bulletin (2004), 48(5-6), 465-470

A N-15 tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica ... [more ▼]

A N-15 tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement because, leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural recolonisation processes. The increase of the N-15 content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots). (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailNitrogen enrichment, boron depletion and magnetic fields in slowly-rotating B-type dwarfs
Morel, Thierry ULg; Hubrig, S.; Briquet, Maryline ULg

in Astronomy and Astrophysics (2008), 481

Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to ... [more ▼]

Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to theoretical expectations, we present a detailed and fully-homogeneous, NLTE abundance analysis of 20 early B-type dwarfs and (sub)giants that reveals the existence of a population of nitrogen-rich and boron-depleted, yet intrinsically slowly-rotating objects. The low-rotation rate of several of these stars is firmly established, either from the occurrence of phase-locked UV wind line-profile variations, which can be ascribed to rotational modulation, or from theoretical modelling in the pulsating variables. The observational data presently available suggest a higher incidence of chemical peculiarities in stars with a (weak) detected magnetic field. This opens the possibility that magnetic phenomena are important in altering the photospheric abundances of early B dwarfs, even for surface field strengths at the one hundred Gauss level. However, further spectropolarimetric observations are needed to assess the validity of this hypothesis. [less ▲]

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See detailNitrogen excess in slowly-rotating beta Cephei stars: deep mixing or diffusion?
Morel, Thierry ULg; Butler, K.; Aerts, C. et al

in Communications in Asteroseismology (2007), 150

We present the results of an NLTE abundance study of a small sample of β Cephei stars, which point to the existence of a population of slowly-rotating B-type pulsators exhibiting a significant amount of ... [more ▼]

We present the results of an NLTE abundance study of a small sample of β Cephei stars, which point to the existence of a population of slowly-rotating B-type pulsators exhibiting a significant amount of nitrogen-enriched material at their surface. Although the origin of this nitrogen excess remains unclear, an overabundance preferentially occurring in stars with a detected magnetic field seems to emerge at this stage. Full details can be found in Morel et al. (2006). [less ▲]

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See detailNitrogen excretions in dairy cows on a rotational grazing system: effects of fertilization type, days in the paddock and time period.
Dufrasne, Isabelle ULg; Robaye, Vincent ULg; Istasse, Louis ULg et al

in Schnyder, Hans; Isselstein, J.; Taube, F. (Eds.) et al Grassland in a changing world (2010, September)

The present study aims to quantify nitrogen (N) excretions in dairy cows on a rotational grazing system with different types of fertilization (mineral N, slurry and compost) after 3 or 5 days in the ... [more ▼]

The present study aims to quantify nitrogen (N) excretions in dairy cows on a rotational grazing system with different types of fertilization (mineral N, slurry and compost) after 3 or 5 days in the paddock and during two different periods in June and September. Individual samples of faeces and urine were collected to assess N excretions from cows in the paddocks. The urea content in milk from the tank or from the individual cows was also measured. N intake was higher on day 3 compared to day 5 (465 vs 425 g d-1, P<0.001) and in September as compared to June (488 vs 425 g d-1, P<0.001) but was not influenced by the fertilization type. The amount of excreted urinary N was significantly higher in the mineral N group than in the two other groups (272 vs 226 g d-1; P<0.001). The N excretion in faeces and urines decreased with days (92 vs 84 g d-1, P<0.01; 256 vs 228 g d-1, P<0.001 respectively for days 3 and 5). Urinary N excretion was lower in June than in September (181 vs 302 g d-1, P<0.001) while the N excretion in the faeces was higher (96 vs 80 g d-1, P<0.01). [less ▲]

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