Search results for "carbon"
showing 10 items of 6057 documents
Mesurer le temps de l'âge du Bronze
2022
Cette question de la mesure du temps reste une préoccupation majeure des archéologues et des spécialistes de l'âge du Bronze bien sûr. Si, globalement, cette période occupe en France une plage de quinze siècles environ, calée entre 2 300 et 800 avant notre ère, il convient toujours de préciser les limites des étapes majeures de l'évolution des sociétés de l'âge du Bronze, mais également de mieux apprécier la place réelle dans le temps des sites étudiés. La question, par exemple, du début de l'âge du Bronze reste toujours une problématique d'actualité qui occupe nos débats, ainsi que parfois ceux de nos collègues néolithiciens. Si on accepte, comme c' est de plus en plus le cas, que le Campa…
Long-term impacts of increased timber harvests on ecosystem services and biodiversity : A scenario study based on national forest inventory data
2020
The transition to a climate-neutral economy is expected to increase future timber demands and endanger the multifunctionality of forests. National scenario analyses are needed to determine long-term forest management impacts and support forest policy making in defining guidelines for the sustainable provision of forests’ ecosystem services and biodiversity (ESB). Using national forestry inventory data, the forest management model MASSIMO and a model to estimate harvesting costs, we simulated forest development in Switzerland under five politically relevant timber harvesting scenarios until 2106 (business as usual and four increased timber mobilisation scenarios). Model results were analysed…
Denitrifying microbial communities along a boreal stream with varying land-use
2019
Streams have an important role in regulating nitrogen (N) transportation from terrestrial ecosystems to downstream waters. Here, we examined how catchment land-use affects potential denitrification rates and the function and composition of denitrifier communities in boreal stream sediments, using stable isotope incubations and qPCR and 454-pyrosequencing targeted on nirS, nirK and nosZ genes. Although land-use influenced the water chemistry as higher nitrite + nitrate (NO x − ) concentration at the agriculture-affected sampling point, sediment organic matter content was found to be the key factor in regulating potential denitrification rates. However, the abundance as well as the diversity …
Enhanced nitrogen removal of low carbon wastewater in denitrification bioreactors by utilizing industrial waste toward circular economy
2020
Aquaculture needs practical solutions for nutrient removal to achieve sustainable fish production. Passive denitrifying bioreactors may provide an ecological, low-cost and low-maintenance approach for wastewater nitrogen removal. However, innovative organic materials are needed to enhance nitrate removal from the low carbon effluents in intensive recirculating aquaculture systems (RAS). In this study, we tested three additional carbon sources, including biochar, dried Sphagnum sp. moss and industrial potato residues, to enhance the performance of woodchip bioreactors treating the low carbon RAS wastewater. We assessed nitrate (NO3−) removal and microbial community composition during a one-y…
Environmental control on granular clinoforms of ancient carbonate shelves
2006
The purpose of this paper is to document the influence of depositional environments on shallow-water, low-relief clinoforms from the description of five ancient carbonate platforms: the Neoproterozoic (Namibia), Middle Jurassic (France), Lower Cretaceous (France), Upper Cretaceous (Oman) and Miocene (Turkey). These examples have been investigated on the basis of field observations. The clinoforms are described with reference to geometric and compositional attributes: declivity, shape, height, sedimentary structures, sediment fabric and components. The results show great variability in stratal geometry, declivity and facies distribution: (1) depositional profiles vary from exponential, to si…
CCDC 713845: Experimental Crystal Structure Determination
2016
Related Article: Denys Mavrynsky, Mari Päiviö, Katri Lundell, Reijo Sillanpää, Liisa T. Kanerva, Reko Leino|2009|Eur.J.Org.Chem.|2009|1317|doi:10.1002/ejoc.200801248
Heat-resistant unfired phosphate ceramics with carbon nanotubes for electromagnetic application
2014
Composite materials, containing low concentrations of carbon nanotubes (CNTs) of three different diameters and heat-resistant phosphate ceramic as a matrix were prepared by cold-pressing method. Their dielectric properties were studied at room temperature in a wide frequency range (20 Hz–1 MHz). It was found experimentally and proved theoretically via modeling of the composites as a random capacitor–resistor–diode network that electrical percolation concentration depends significantly on the diameter of the nanoinclusions. The main conclusion is that the best candidate providing both the lower percolation threshold and high absolute values of ac conductivity is thinner carbon nanotubes (in …
Dielectrophoresis as an assembly method for carbon nanotube memory elements
2010
The experiments described in this Master's thesis aim to assess the practicality of using dielectrophoresis (DEP) for assembling memory elements from carbon nanotubes (CNTs). These elements were field-effect transistors (FETs) with a wide hysteresis window. The devices assessed were made on a silicon substrate with a HfO2 - TiO2 - HfO2 gate dielectric layer to ensure a predictable hysteresis for memory operation. The FETs were used for further research in regard to environmental effects in their operation. An average yield of 12.5 % over 26 different trapping attempts, a total of 650 gaps, was achieved for single trapped CNTs in a two-electrode configuration with a 1 µm gap between electrod…
Gas geochemistry and preliminary CO2 output estimation from the island of Kos (Greece)
2017
Several gas samples have been collected from natural gas manifestations at the island of Kos. Most of them are found underwater along the southern coast of the island. On land two anomalous degassing areas have been recognized. These are characterised by lack of vegetation and after long dry periods by the presence of sulfate salts efflorescences. Almost all the gases are CO2-dominated (CO2 ranging from 88 to 99%) with minor amounts of N2 (up to 7%) and CH4 (up to 2.6%). Only the on-land manifestations have also significant contents of H2 (up to 0.2%) and H2S (up to 0.3%). Only one underwater manifestation is N2-dominated (61-99%) with CH4 (0.6-11%) and low CO2 (0.1-26%). The isotopic compo…
Reactions of Terphenyl-Substituted Digallene AriPr4GaGaAriPr4 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with Transition Metal Carbonyls and Theoretical In…
2016
The neutral digallene AriPr4GaGaAriPr4 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) was shown to react at ca. 25 °C in pentane solution with group 6 transition metal carbonyl complexes M(CO)6 (M = Cr, Mo, W) under UV irradiation to afford compounds of the general formula trans-[M(GaAriPr4)2(CO)4] in modest yields. The bis(gallanediyl) complexes were characterized spectroscopically and by X-ray crystallography, which demonstrated that they were isostructural. In each complex, the gallium atom is two-coordinate with essentially linear geometry, which is relatively rare for gallanediyl-substituted transition metal species. The experimental data show that the gallanediyl ligand :GaAriPr4 behaves as a g…