Articles de revues sur le sujet « Cycle de carbone »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Cycle de carbone.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Cycle de carbone ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Bailly, Sean. « Un cycle en pur carbone ». Pour la Science N° 504 - octobre, no 10 (10 janvier 2019) : 9b. http://dx.doi.org/10.3917/pls.504.0009b.
Texte intégral
2
Friedlingstein, Pierre, Laurent BOPP et Patricia CADULE. « Changement climatique et cycle du carbone ». La Météorologie 8, no 58 (2007) : 21. http://dx.doi.org/10.4267/2042/18204.
Texte intégral
3
Bard, Édouard, et Richard Sempéré. « Le cycle du carbone dans l’océan ». La lettre du Collège de France, no 40 (2 septembre 2015) : 38–39. http://dx.doi.org/10.4000/lettre-cdf.2102.
Texte intégral
4
Schlamadinger, Bernhard, Lorenza Canella, Gregg Marland et Josef Spitzer. « Bioenergy strategies and the global carbon cycle. / Stratégies bioénergétiques et cycle global du carbone ». Sciences Géologiques. Bulletin 50, no 1 (1997) : 157–82. http://dx.doi.org/10.3406/sgeol.1997.1951.
Texte intégral
5
Jonas, KOALA, KAGAMBEGA O. Raymond et SANOU Lassina. « Distribution des stocks de carbone du sol et de la biomasse racinaire dans un parc agroforestier à Prosopis africana (Guill., et Rich.) Taub au Burkina Faso, Afrique de l’Ouest ». Journal of Applied Biosciences 160 (30 avril 2021) : 16482–94. http://dx.doi.org/10.35759/jabs.160.5.
Texte intégralRésumé :
Objectif : Cette présente étude visait à déterminer la distribution verticale des stocks de carbone organique du sol et de la biomasse racinaire dans un parc agroforestière à Prosopis africana (Guill., et Rich.) Taub au Burkina Faso. Méthodologie et Résultats : L’étude a été menée à Saria sur un dispositif factoriel avec 3 répétitions. L’échantillonnage des racines et du sol a été fait par l’extraction de monolithes sur 5 couches à une profondeur de 150 cm. Les résultats montrent que la profondeur a influencé les stocks de carbone. La couche 0-50 cm renferme 91% du stock total de carbone de la biomasse racinaire. Les stocks de Carbone Organique du Sol (COS) le plus élevé a été enregistré dans la couche 80-120 cm (26,59±7,94 tC ha-1), contre 8,74±6,05 tC ha-1 dans la couche 0-20 cm. Conclusion et implication des résultats : Les résultats montrent que les parcs agroforestiers étudiés ont un fort potentiel de séquestration de carbone. Cependant, les éventuels projets de carbone dans les parcs agroforestiers devront se focaliser sur la biomasse végétale aérienne et souterraine car le carbone organique du sol parait ne pas être influencé par les différents aménagements. Aussi pour une bonne gestion de ces stocks de carbone, des études complémentaires doivent être menées en vue de comprendre le cycle de de renouvellement des racines fines des parcs agroforestiers afin de de mesurer les flux de carbone organique du sol dans les parcs agroforestiers. Mots clés : Carbone organique du sol; Parc agroforestier, Prosopis africana, séquestration de carbone ; Biomasse racinaire 16482 Koala et al., J. Appl. Biosci. Vol.160 :2021 Distribution des stocks de carbone du sol et de la biomasse racinaire dans un parc agroforestier à Prosopis africana (Guill., et Rich.) Taub au Burkina Faso, Afrique de l’Ouest Distribution of carbon stocks from soil and root biomass in Prosopis africana (Guill., And Rich.) Taub agroforestry parkland in Burkina Faso, West Africa. ABSTRACT Objectives The aim of this study was to determine soil organic carbon stocks and root biomass carbon vertical distribution in an agroforestry parkland of Prosopis africana (Guill., And Rich.) Taub in Burkina Faso. Methodology and Results: The study was carried out in Saria on factorial design with 3 replicates. Root and soil sampling was done by extracting monoliths in 5-layer up to 150 cm depth. Results show that depth influenced carbon stocks. 0-50 cm layer contains 91% of root biomass total carbon stock. Highest soil Organic Carbon (SOC) stocks were recorded in 80-120 cm layer (26.59 ± 7.94 tC ha-1), compared to 8.74 ± 6.05 tC ha-1 in 0-20 cm layer. Conclusions and application of findings: Our results show that agroforestry parklands have a high carbon sequestration potential. However, any carbon projects in agroforestry parklands have to focus on trees above-ground and below-ground biomass because soil organic carbon does not influenced by management. Also for good management of these carbon stocks, additional studies must be carried out in order to understand the renewal cycle of fine roots in agroforestry parks in order to measure organic carbon flow from soil in agroforestry parklands. Keywords: Soil organic carbon; Agroforestry parklands, Prosopis africana, carbon sequestration; Root biomass INTRODUCTION L’agroforesterie est un système d’utilisation des terres traditionnel qui est toujours utilisé de nos jours par les populations (Santoro et al., 2020). Elle est considérée comme un système durable car contribuant à lutter contre la dégradation des terres. Sa contribution à l’amélioration à la productivité de l’agriculture est bien reconnue de nos jours (Montagnini and Nair, 2004). L’amélioration de la productivité est due à l’augmentation de la matière organique et au recyclage des éléments
6
Viovy, Nicolas, et Nathalie de Noblet. « Coupling water and carbon cycle in the biosphere. / Couplage du cycle de l'eau et du carbone dans la biosphère ». Sciences Géologiques. Bulletin 50, no 1 (1997) : 109–21. http://dx.doi.org/10.3406/sgeol.1997.1948.
Texte intégral
7
Mavouroulou Quentin, Moundounga, Ngomanda Alfred et Lepengue Nicaise Alexis. « Etat des Lieux des Incertitudes Liées à l’Estimation de la Biomasse des Arbres (Revue Bibliographique) ». European Scientific Journal, ESJ 19, no 6 (28 février 2023) : 60. http://dx.doi.org/10.19044/esj.2023.v19n6p60.
Texte intégralRésumé :
The quantification of forest carbon stocks and fluxes is absolutely essential to understand the role that forests play in the global carbon cycle and to put in place effective policies to mitigate global warming induced by the increase in greenhouse gases of anthropogenic origin. This study aims to present the current state of knowledge on the uncertainties associated with quantifying forest carbon, particularly in tropical forests. Several studies show that the uncertainties on the carbon stocks and fluxes sequestered in tropical forests are extremely large, estimated respectively at 188 and 272 billion tonnes of carbon and between 0.17 and 1.16 billion tonnes of carbon dioxide. These huge uncertainties are probably related to the methods used to quantify the biomass of living trees. In almost all studies on forest carbon, the biomass of trees is never really measured in the field, but rather estimated using mathematical models or allometric equations which leads to an uncertainty of about 20% on the estimated biomass. Our study also shows that the reduction of these uncertainties could depend on several factors such as (i) the aboveground biomass data collection method (ii) the measurement of tree size attributes (diameter and height) and tree traits. species (specific density of the wood, size of the canopy) during forest inventories, (iii) the mathematical form and quality of adjustment of the allometric models (specific error of the model) used, and (iv) possibly an inadequacy between tree diameter structure in model calibration data and in forest inventory data. However, the absence of studies that have measured the total biomass of a forest at a fixed spatial scale (example 1 ha) does not currently allow an assessment of the contribution of each source of error to the total uncertainty of the final carbon estimate.
La quantification des stocks et flux de carbone forestier avec précision est absolument essentielle pour comprendre le rôle que jouent les forêts dans le cycle global du carbone et pour mettre en place des politiques efficaces d’atténuation du réchauffement climatique mondial induit par l’augmentation des gaz à effet de serre d’origine anthropique. Cette étude vise à présenter l’état actuel des connaissances sur les incertitudes associées à la quantification du carbone forestier, en particulier dans les forêts tropicales. Plusieurs études montrent que les incertitudes sur les stocks et flux de carbone séquestrés dans les forêts tropicales sont extrêmement larges, estimés respectivement 188 et 272 milliards de tonnes de carbone et entre 0.17 et 1.16 milliards de tonnes de gaz carbonique. Ces énormes incertitudes sont sans doute liées aux méthodes utilisées pour quantifier la biomasse des arbres vivants. Dans la quasi-totalité des études sur le carbone forestier, la biomasse des arbres n’est réellement jamais mesurée sur le terrain, mais plutôt estimés à l’aide des modèles mathématiques ou équations allométriques qui entraine une incertitude d’environ 20% sur l’estimation de la biomasse. Notre étude montre aussi que la réduction de ces incertitudes pourrait dépendre de plusieurs facteurs tels que: (i) la méthode de collecte des données de la biomasse aérienne (ii) la mesure des attributs de taille (diamètre et hauteur) des arbres et traits d’espèces (densité du spécifique du bois, taille de la canopée) lors des inventaires forestiers, (iii) la forme mathématique et qualité d’ajustement des modèles allométriques (erreur propre du modèle) employés, et (iv) possiblement d’une inadéquation entre structure diamétrique des arbres dans les données de calibration des modèles et dans les données inventaires forestiers. Toutefois, l’absence d’études ayant mesuré la biomasse totale d’une forêt à une échelle spatiale fixée (exemple 1 ha) ne permet pas actuellement d’évaluer la contribution de chaque source d’erreurs sur l’incertitude totale de l’estimation finale de carbone.
8
Séférian, Roland, Matthias Rocher, Nicolas Metzl et Philippe Ciais. « Évolution récente du cycle du carbone planétaire : facteurs humains et naturels ». La Météorologie 8, no 93 (2016) : 3. http://dx.doi.org/10.4267/2042/59931.
Texte intégral
9
DOLLÉ, J. B., J. AGABRIEL, J. L. PEYRAUD, P. FAVERDIN, V. MANNEVILLE, C. RAISON, A. GAC et A. LE GALL. « Les gaz à effet de serre en élevage bovin : évaluation et leviers d'action ». INRAE Productions Animales 24, no 5 (8 décembre 2011) : 415–32. http://dx.doi.org/10.20870/productions-animales.2011.24.5.3275.
Texte intégralRésumé :
Le contexte environnemental actuel, tant politique (objectifs de réduction des émissions de gaz à effet de serre) que sociétal (informationdu consommateur), nécessite de préciser les impacts de l'activité d'élevage bovin en matière de changement climatique. L'enjeuest de connaître précisément les niveaux d'émissions de gaz à effet de serre (GES) et de stockage de carbone, des différents modes deproduction. Pour cela, une évaluation basée sur la méthodologie de l'Analyse du Cycle de Vie (ACV) est mise au point à l'échelle dusystème d'élevage. Cette approche permet d'avoir une vision globale de l'activité d'élevage intégrant l'ensemble des processus interneset externes au fonctionnement de l'exploitation. Ainsi pour les systèmes laitiers français, l'empreinte carbone brute du lait est enmoyenne de 1,26 kg CO2/kg de lait. La prise en compte du stockage de carbone sous les prairies et les haies se traduit par une compensationcomprise entre 6 et 43% selon les systèmes, en fonction de la part de prairies. L'empreinte carbone nette du lait françaisest alors en moyenne de 1,0 kg CO2/kg de lait. Dans les systèmes bovins viande français, l'empreinte carbone brute est comprise entre14,8 et 16,5 kg CO2/kg viande vive en fonction du système de production (naisseur vs naisseur/engraisseur). Après prise en comptedu stockage de carbone qui permet une compensation comprise entre 24 et 53%, l'empreinte carbone nette est comprise entre 7,9 et11,3 kg CO2/kg viande vive. De nombreux leviers d'action sont identifiés dans les systèmes d'élevage de ruminants pour réduire l'empreintecarbone des produits au portail de la ferme. Certains concernent une optimisation des systèmes de production (ajustementdes apports alimentaires, gestion de la fertilisation…) et se traduisent par des économies en matière d'intrants. D'autres nécessitentla mise en place de nouvelles technologies et se traduiront donc par un investissement ou un coût de fonctionnement supérieur auxschémas actuels de production.
10
Vincent, Julia, Béatrice Colin, Isabelle Lanneluc, Philippe Refait, René Sabot, Marc Jeannin et Sophie Sablé. « La biocalcification bactérienne en milieu marin et ses applications ». Matériaux & ; Techniques 110, no 6 (2022) : 606. http://dx.doi.org/10.1051/mattech/2023004.
Texte intégralRésumé :
La précipitation du carbonate de calcium (CaCO3) biologiquement induite en milieu marin joue un rôle important dans le cycle biogéochimique du carbone. Cette biocalcification est gouvernée par quatre facteurs clés : le taux de carbone inorganique dissous dont dépend le taux de carbonates (CO32−) dans le système, le taux d’ions calciques (Ca2+), le pH et la disponibilité des sites de nucléation c’est-à-dire des zones de cristallisation primaire de la phase solide du minéral. Les bactéries impliquées dans la biocalcification marine vont alors agir sur un ou plusieurs de ces facteurs. Ce processus naturel, qui se produit dans divers contextes géologiques, peut être imité afin de développer un certain nombre de technologies permettant la séquestration des métaux lourds, la protection des métaux contre la corrosion, la restauration et le renforcement de matériaux préexistants et la consolidation de matériaux granulaires. Cette étude passe en revue les différentes activités métaboliques microbiennes menant à la précipitation du CaCO3 ainsi que leurs applications potentielles en milieu marin.
11
Sica, Arianna. « Environmental and economic benefits of Green Public procurement through the Bilan Carbone and Life Cycle Costing methodologies : a case study for Arpa Piemonte ». EUROPEAN JOURNAL OF PUBLIC PROCUREMENT MARKETS 1, no 4 (2023) : 118–30. http://dx.doi.org/10.54611/yrgf9283.
Texte intégralRésumé :
The main objective of this article is to analyse the economic and environmental benefits associated with the implementation of Green Public Procurement and Minimum Environmental Criteria in a specific tender published by Arpa Piemonte for its headquarters in the city of Turin. The focus lies on the modernization of the internal lighting system shifting from CFL to LED technology: the analysis of environmental aspects measures the reduction of GHG emissions through Bilan Carbone; the economic benefits are analysed with the Life Cycle Costing tool of the European Commission.
12
Sica, Arianna. « Environmental and economic benefits of Green Public procurement through the Bilan Carbone and Life Cycle Costing methodologies : a case study for Arpa Piemonte ». EUROPEAN JOURNAL OF PUBLIC PROCUREMENT MARKETS 1, no 4 (2023) : 118–30. http://dx.doi.org/10.54611/jyuh5456.
Texte intégralRésumé :
The main objective of this article is to analyse the economic and environmental benefits associated with the implementation of Green Public Procurement and Minimum Environmental Criteria in a specific tender published by Arpa Piemonte for its headquarters in the city of Turin. The focus lies on the modernization of the internal lighting system shifting from CFL to LED technology: the analysis of environmental aspects measures the reduction of GHG emissions through Bilan Carbone; the economic benefits are analysed with the Life Cycle Costing tool of the European Commission.
13
Micheau, François, Jérôme Porteret et Julien Saillard. « Protéger et gérer les zones humides pour s’adapter et atténuer les effets du changement climatique sur le grand cycle de l’eau, une action des Conservatoires d’espaces naturels ». Annales des Mines - Responsabilité et environnement N° 112, no 4 (25 octobre 2023) : 99–103. http://dx.doi.org/10.3917/re1.112.0099.
Texte intégralRésumé :
À travers plusieurs exemples concrets de préservation et de restauration des milieux humides en France, menés par les Conservatoires d’espaces naturels, cet article propose de voir les zones humides à la fois comme objet du changement climatique, subissant directement ou indirectement les effets délétères sur ses fonctions, mais également comme sujet du changement climatique, constituant une solution d’adaptation et d’atténuation du changement climatique, notamment par le stockage de carbone.
14
Zebbar, Djallel, Sahraoui Kherris, Kouider Mostefa, Sidali Horr et Mhamed Guettaf. « Etude théorique du cycle de Brayton irréversible avec régénération d'une centrale thermique à concentration solaire ». Journal of Renewable Energies 19, no 2 (9 janvier 2024) : 199–210. http://dx.doi.org/10.54966/jreen.v19i2.561.
Texte intégralRésumé :
Tout comme beaucoup de pays arabes et africains, l’Algérie est confrontée dès maintenant à des défis économiques et énergétiques sans précédents. Ces défis vont être accentués avec le déclin des réserves de gaz naturel et du pétrole. Dans ces circonstances, la conservation de l’indépendance énergétique du pays et sa prospérité économique et sociale dans un avenir proche se jouent dès aujourd’hui. Dans ce contexte, la promotion de la filière des énergies renouvelables et plus particulièrement de la filière thermique solaire est très prometteuse. Le présent travail s’aligne sur les mêmes objectifs susmentionnés. Il est consacré à l’étude thermodynamique du cycle irréversible avec régénération de Brayton utilisé dans les centrales thermiques de production de puissance à concentration solaire. Les performances du cycle ont été analysées pour trois différents agents thermiques à savoir: l’hélium, l’air et le dioxyde de carbone. Il en ressort que le cycle de Brayton solaire irréversible avec régénération est plus performant avec de l’hélium comme fluide de travail avec les valeurs basses des rapports de pressions incluses entre 3 et 5 et de températures avoisinant 0.25. Pour les valeurs du rapport de pressions comprises entre 9 et 13 et les valeurs des rapports de températures supérieurs à 0.3 le cycle est opérationnel et plus performant avec du CO2 en qualité de fluide de travail.
15
Sudriès, Marie, Florence Ligozat et David Cross. « Les enjeux de l’enseignement-apprentissage de la transformation chimique au secondaire I : regards croisés sur les prescriptions officielles et ressources formelles en Suisse romande et en France ». Swiss Journal of Educational Research 45, no 1 (20 juin 2023) : 64–82. http://dx.doi.org/10.24452/sjer.45.1.6.
Texte intégralRésumé :
Cet article propose d’interroger les conditions d’enseignement-apprentissage du concept de transformation chimique par des élèves de 13-15 ans, en Suisse romande et en France. L’analyse des prescriptions officielles et des ressources formelles nous montrent que, si ce concept est au cœur du curriculum de chimie dès le secondaire I, il est également présent en biologie/géographie/SVT, via la notion de « cycle du carbone », objet au cœur de questions complexes en lien avec le réchauffement climatique. Au-delà de l’enseignement-apprentissage de la transformation chimique dans le cadre strictement disciplinaire de la chimie, il s’agit donc de comprendre comment ce concept peut soutenir le traitement de questions complexes et d’ainsi contribuer à la formation des citoyen·ne·s.
16
Brioude, J., J. P. Cammas et O. R. Cooper. « Stratosphere-troposphere exchange in a summertime extratropical low : analysis ». Atmospheric Chemistry and Physics Discussions 5, no 6 (29 novembre 2005) : 12465–503. http://dx.doi.org/10.5194/acpd-5-12465-2005.
Texte intégralRésumé :
Abstract. Ozone and carbone monoxide measurements sampled during two commercial flights in airstreams of a summertime midlatitude cyclone are analysed with a lagrangian-based study (backward trajectories and a Reverse Domain Filling technique) to gain a comprehensive understanding of transport effects on trace gas distributions. The study demonstrates that summertime cyclones can be associated with deep stratosphere-troposphere transport. A tropopause fold is sampled twice in its life cycle, once in the lower troposphere (O3≃100 ppbv; CO≃90 ppbv) in the dry airstream of the cyclone, and again in the upper troposphere (O3≃200 ppbv; CO≃90 ppbv) on the northern side of the large scale potential vorticity feature associated with baroclinic development. In agreement to the maritime development of the cyclone, the chemical composition of the anticyclonic part outflow of the warm conveyor belt (O3≃40 ppbv; CO≃85 ppbv) corresponds to the lowest mixing ratios of both ozone and carbone monoxide in upper tropospheric airborne observations. The uncertain degree of confidence of the Lagrangian-based technique applied to a 100 km segment of upper level airborne observations with high ozone (200 ppbv) and relatively low CO (80 ppbv) observed northwest of the cyclone prevents to identify the ozone enrichment process of air parcels embedded in the cyclonic part of the upper level outflow of the warm conveyor belt. Different hypotheses of stratosphere-troposphere exchange are discussed.
17
Brion, N., et G. Billen. « Une réévaluation de la methode d'incorporation de H14C03- pour mesurer la nitrification autotrophe et son application pour estimer des biomasses de bactéries nitrifiantes ». Revue des sciences de l'eau 11, no 2 (12 avril 2005) : 283–302. http://dx.doi.org/10.7202/705308ar.
Texte intégralRésumé :
Le processus de nitrification joue un rôle essentiel dans le cycle de l'azote dans les milieux aquatiques naturels. La mesure de l'activité nitrifiante est une étape obligée pour bien comprendre et quantifier les flux d'azote dans ces milieux. Ce travail présente une réévaluation de la méthode de mesure de l'activité nitrifiante autotrophe par la méthode d'incorporation de bicarbonate marqué au 14C et son application pour estimer des biomasses de bactéries nitrifiantes. La validité générale de la méthode a été démontrée par des tests menés sur des inhibiteurs de nitrification qui ont montré que l'utilisation combinée de N-serve (5 ppm) et de chlorate (10 mM) inhibait de manière complète et spécifique l'oxydation d'azote et l'incorporation de carbone des deux groupes de bactéries nitrifiantes. Un facteur de rendement (carbone incorporé par azote oxydé) de 0,1 mole C/mole N a également été déterminé sur des cultures pures de bactéries nitrosantes et nitratantes. Pour l'activité potentielle, en particulier, les conditions optimales pour la mesure d'activité nitrifiante ont également été établis: un pH entre 7 et 8, une température entre 20 et 30°C, une concentration en ammonium d'au moins 1 mmol/l et en oxygène d'au moins 6 mg/l. Une relation entre les mesures d'activité nitrifiante potentielle et la biomasse des bactéries nitrifiantes a été établie sur culture pure. Elle montre que dans les conditions de mesures de l'activité potentielle, 1 µg C de bactéries nitrifiantes oxyde 0,04 µmol N/h
18
Allemane, H., M. Prados-Ramirez, J. P. Croué et B. Legube. « Recherche et identification des premiers sous-produits d'oxydation de l'isoproturon par le système ozone/peroxyde d'hydrogène ». Revue des sciences de l'eau 8, no 3 (12 avril 2005) : 315–31. http://dx.doi.org/10.7202/705226ar.
Texte intégralRésumé :
Une solution aqueuse tamponnée par des phosphates (pH initial - 8) dopée en isoproturon (N- (isopropyl-4-phényl)-N-N'-diméthylurée) (~ 20 mg 1-1), a été oxydée par le système perozone, combinant l'ozone et le peroxyde d'hydrogène dans un rapport molaire de 0,5 à 0,6 moles de H2O2 par mole d'ozone. Les disparitions du composé parent, du carbone organique total (COT), du carbone total (CT) et de la consommation d'ozone, ont été suivies au cours de l'oxydation. Les premiers sous-produits d'oxydation, ceux susceptibles de conserver une formulation moléculaire proche de celle du composé initial, et par conséquent de posséder encore une activité toxique, ont été isolés et caractérisés par chromatographie gazeuse couplée à la spectrométrie de masse. Il a été trouvé que l'isoproturon requiert un taux d'oxydation molaire de 10 moles d'ozone par mole d'isoproturon introduit, pour obtenir une élimination complète de cet herbicide. En revanche, le COT n'est pratiquement pas minéralisé, même avec de très forts taux d'ozone, ce qui indique la présence dans le milieu de sous-produits rémanents. La plupart des premiers sous-produits d'oxydation détectés conservent le cycle aromatique dans leur structure, et au moins un atome d'azote, et sont présents à des concentrations significatives. Ces composés semblent aussi réactifs que l'isoproturon vis-à-vis de la perozonation puisqu'ils disparaissent lorsqu'on prolonge l'oxydation. De plus, l'identification de ces sous-produits laisse supposer que l'attaque des radicaux hydroxyles générés par le procédé perozone, entraîne la rupture d'une liaison C-N ou d'une liaison C-H, conduisant à la formation de composés oxygénés.
19
Borrelly, R., I. Biron, P. Delaneau et B. J. Thomas. « Dosage du carbone en solution dans les aciers extra-doux par mesure du pouvoir thermoélectrique. Application à la détermination des teneurs en carbone en solution à différentes étapes d’un cycle de recuit continu ». Revue de Métallurgie 90, no 5 (mai 1993) : 685–96. http://dx.doi.org/10.1051/metal/199390050685.
Texte intégral
20
Mulkerin, Daniel L., Jason J. Bergsbaken, Jessica A. Fischer, Mary J. Mulkerin, Aaron M. Bohler et Mary S. Mably. « Multidisciplinary Optimization of Oral Chemotherapy Delivery at the University of Wisconsin Carbone Cancer Center ». Journal of Oncology Practice 12, no 10 (octobre 2016) : e912-e923. http://dx.doi.org/10.1200/jop.2016.013748.
Texte intégralRésumé :
Purpose: Use of oral chemotherapy is expanding and offers advantages while posing unique safety challenges. ASCO and the Oncology Nursing Society jointly published safety standards for administering chemotherapy that offer a framework for improving oral chemotherapy practice at the University of Wisconsin Carbone Cancer Center. Methods: With the goal of improving safety, quality, and uniformity within our oral chemotherapy practice, we conducted a gap analysis comparing our practice against ASCO/Oncology Nursing Society guidelines. Areas for improvement were addressed by multidisciplinary workgroups that focused on education, workflows, and information technology. Recommendations and process changes included defining chemotherapy, standardizing patient and caregiver education, mandating the use of comprehensive electronic order sets, and standardizing documentation for dose modification. Revised processes allow pharmacists to review all orders for oral chemotherapy, and they support monitoring adherence and toxicity by using a library of scripted materials. Results: Between August 2015 and January 2016, revised processes were implemented across the University of Wisconsin Carbone Cancer Center clinics. The following are key performance indicators: 92.5% of oral chemotherapy orders (n = 1,216) were initiated within comprehensive electronic order sets (N = 1,315), 89.2% compliance with informed consent was achieved, 14.7% of orders (n = 193) required an average of 4.4 minutes review time by the pharmacist, and 100% compliance with first-cycle monitoring of adherence and toxicity was achieved. Conclusion: We closed significant gaps between institutional practice and published standards for our oral chemotherapy practice and experienced steady improvement and sustainable performance in key metrics. We created an electronic definition of oral chemotherapies that allowed us to leverage our electronic health records. We believe our tools are broadly applicable.
21
Keenan, T. D., et R. E. Carbone. « Propagation and Diurnal Evolution of Warm Season Cloudiness in the Australian and Maritime Continent Region ». Monthly Weather Review 136, no 3 (1 mars 2008) : 973–94. http://dx.doi.org/10.1175/2007mwr2152.1.
Texte intégralRésumé :
Abstract Warm season cold cloud-top climatology in the Austral–Indonesian region is examined for evidence of propagating modes of precipitation that originate from elevated heat sources and the diurnal heating cycle. Using satellite-inferred cloudiness from the period 1996–2001 as a proxy for rainfall, this coherent regeneration process and subsequent event propagation is found to consistently occur from the midlatitudes (30°–40°S) to the tropics (10°–20°S) in the Austral region. Given favorable environmental shear at midlatitudes, long-lived eastward-propagating events are observed to occur regularly with a span and duration typically larger than observed by Carbone et al. The genesis of these events, while intermittent, is directly related to elevated heat sources and the diurnal cycle, similar to the United States. However, given the relatively flat terrain of Australia, an elevated heat source is often insufficient, thus increasing the relative influence of transient synoptic forcing. In the tropics, the thermal forcing associated with elevated terrain found over the islands of the Maritime Continent and the land–sea interface is increasingly dominant on daily basis. While eastward- and westward-propagating events are found in the more varied environment of the monsoon regime, evidence for meridionally propagating modes is also found. In this manner, complex interactions occur that modify the location and timing of clouds that develop over neighboring oceanic and continental locations. The impact of convection initially linked to the New Guinea highlands and subsequently impacting the Java Sea region is particularly evident affecting the observed diurnal cycle. The subtropics show characteristics intermediate between the above extremes. With the seasonal cycle, the spring environment favors eastward-propagating events but in summer there is an increasing frequency of diurnally forced quasi-stationary development over elevated terrain enhanced by favorable synoptic conditions. Overall the subtropical summer events have a shorter duration and span than their spring counterparts. The increased environmental steering winds and shear in spring are thought to be the primary reason.
22
Arie, Arenst Andreas, Kevin Hazel, Hans Kristianto, Henky Muljana et Lorenzo Stievano. « Ganyong Starch Derived Hard Carbon Anodes for Sodium Ion Batteries ». Journal of Nanoscience and Nanotechnology 21, no 7 (1 juillet 2021) : 4033–36. http://dx.doi.org/10.1166/jnn.2021.19220.
Texte intégralRésumé :
Hard carbons are one of the most promising carbon anode materials for sodium ion batteries (SIBs) due to the high specific capacity and excellent cycle properties. Among the precursors used to synthesize hard carbon, natural starches are of great interest due to their unique morphologies. In this paper, ganyong starch based hard carbons (GSHC) were prepared by direct carbonization at various temperatures (700–1100) °C. The obtained hard carbons exhibit high reversible capacities of sodium-ion batteries of about 239 mAh g–1 at current density of 0.1 C. after 100 cycles. The excellent cycle profiles are attributed to the unique morphology and defect carbon structures.
23
Engle, Jeff A., Anne M. Traynor, Toby C. Campbell, Kari B. Wisinski, Noelle LoConte, Glenn Liu, George Wilding et Jill M. Kolesar. « Assessment of adherence and relative dose intensity with oral chemotherapy in oncology clinical trials at an academic medical center ». Journal of Oncology Pharmacy Practice 24, no 5 (29 avril 2017) : 348–53. http://dx.doi.org/10.1177/1078155217704989.
Texte intégralRésumé :
Background/Aims Oral chemotherapy is increasingly utilized leaving the patient responsible for self-administering an often complex regimen where adverse effects are common. Non-adherence and reduced relative dose intensity are both associated with poorer outcomes in the community setting but are rarely reported in clinical trials. The purpose of this study is to quantify adherence and relative dose intensity in oncology clinical trials and to determine patient and study related factors that influence adherence and relative dose intensity. Methods Patients were identified from non-industry-funded clinical trials conducted between 1 January 2009 and 31 March 2013 at the University of Wisconsin Carbone Cancer Center. Data were extracted from primary research records. Descriptive statistics and linear regression modeling was performed using SAS 9.4. Results A total of 17 clinical trials and 266 subjects were included. Mean adherence was greater than 97% for the first eight cycles. Mean relative dose intensity was less than 90% for the first cycle and declined over time. Male gender, a performance status of 1 or 2, metastatic disease, and traveling more than 90 miles to reach the cancer center were associated with higher relative dose intensity. Conclusions Patients with cancer enrolled in clinical trials are highly adherent but unlikely to achieve protocol specified relative dose intensity. Given that determining the phase II dose is the primary endpoint of phase I trials, incorporating relative dose intensity into this determination should be considered.
24
Abbas, Mohamed, Noureddine Said et Boussad Boumeddane. « Optimisation d’un moteur Stirling de type gamma ». Journal of Renewable Energies 13, no 1 (25 octobre 2023) : 1–12. http://dx.doi.org/10.54966/jreen.v13i1.174.
Texte intégralRésumé :
La nécessité de réduire les émissions de dioxyde de carbone (CO2) a conduit à revaloriser les moteurs à combustion externe fonctionnant selon le cycle de Stirling. Les moteurs Stirling connaissent depuis peu une vogue nouvelle, car ils sont silencieux, non polluants, acceptent tout type de chaleur externe et demandent peu de maintenance. Ce moteur a été utilisé avec succès pour la conversion de l’énergie solaire en électricité par la technologie dite ‘Dish Stirling System’ qui utilise un moteur Stirling placé au foyer d’un concentrateur parabolique. Dans cette étude, une modélisation dynamique d’un moteur Stirling de type gamma basée une approche quasi stationnaire a été présentée. Ce modèle, qui prend en compte les différentes pertes thermiques et mécaniques dont le moteur Stirling est le siège, a conduit à l’écriture d’important système d’équation algébro différentielles. Le programme de calcul développé sous Matlab a permis, dans le but d’améliorer les performances du moteur Stirling, d’optimiser les paramètres géométriques et physiques, tels que la géométrie des échangeurs, la température du réchauffeur et du refroidisseur, les volumes morts et la vitesse de rotation.
25
Albrecht, Florian, Igor Rončević, Yueze Gao, Fabian Paschke, Alberto Baiardi, Ivano Tavernelli, Shantanu Mishra, Harry L. Anderson et Leo Gross. « The odd-number cyclo[13]carbon and its dimer, cyclo[26]carbon ». Science 384, no 6696 (10 mai 2024) : 677–82. http://dx.doi.org/10.1126/science.ado1399.
Texte intégralRésumé :
Molecular rings of N carbon atoms (cyclo[ N ]carbons, or C N ) are excellent benchmarking systems for testing quantum chemical theoretical methods and valuable precursors to other carbon-rich materials. Odd- N cyclocarbons, which have been elusive to date, are predicted to be even less stable than even- N cyclocarbons. We report the on-surface synthesis of cyclo[13]carbon, C 13 , by manipulation of decachlorofluorene with a scanning probe microscope tip. We elucidated the properties of C 13 by experiment and theoretical modeling. C 13 adopts an open-shell configuration with a triplet ground state and a kinked geometry, which shows different extents of distortion and carbene localization depending on the molecular environment. Moreover, we prepared and characterized the C 13 dimer, cyclo[26]carbon, demonstrating the potential of cyclocarbons and their precursors as building blocks for carbon allotropes.
26
Fey, George Ting Kuo, Yu Yen Lin, Kai Pin Huang, Yi Chuan Lin, T. Prem Kumar, Yung Da Cho et Hsien Ming Kao. « Green Energy Anode Materials : Pyrolytic Carbons Derived from Peanut Shells for Lithium Ion Batteries ». Advanced Materials Research 415-417 (décembre 2011) : 1572–85. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1572.
Texte intégralRésumé :
Disordered carbons prepared by the pyrolysis of peanut shells with and without a porogen were investigated. The first-cycle lithium insertion capacity of the porogen-treated carbon was 3504 mAh/g, and was related to the high surface area (2099 m2/g) of the carbon. It was concluded from x-ray diffraction studies that the extra lithium was stored in the microporous voids in the carbon. The large irreversible capacity for this carbon is believed to be associated with the loss of lithium through its reaction with surface groups as well as with lithium plating and subsequent passive film formation. The impedance profiles of the carbons at various potentials were analyzed and modeled with suitable equivalent circuits. Charge-discharge studies with the porogen-treated carbon, pre-charged and discharged prior to use in coin cells, indicated that the first-cycle reversible capacity was the greatest when the charge-discharge rate was 0.4 C. The carbon maintained capacities of about 325 mAh/g for 20 cycles, and then stabilized around 380 mAh/g for over 70 cycles.
27
Hillaire-Marcel, Claude, Anne de Vernal, Marc Lucotte, Alfonso Mucci, Guy Bilodeau, André Rochon, Sylvain Vallières et Guoping Wu. « Productivité et flux de carbone dans la mer du Labrador au cours des derniers 40 000 ans ». Canadian Journal of Earth Sciences 31, no 1 (1 janvier 1994) : 139–58. http://dx.doi.org/10.1139/e94-012.
Texte intégralRésumé :
Geochemical and micropaleontological analyses of Labrador Sea sediments allowed us to intercalibrate indicators of paleoproductivity and paleofluxes of carbon and to reconstitute biogeochemical fluxes, notably in relation to deep sea circulation changes (Western Boundary Undercurrent and North Atlantic Deep Water). Linear or logarithmic relations are observed between the subrecent fluxes of paleoproductivity indicators (coccoliths, diatoms, dinocysts, 230Th), the 13C content of left-coiling or sinistral Neogloboquadrina pachyderma, the modern surface water carbon production, and the rates of organic and inorganic carbon (Corg, Cinorg) burial. All indicators increase by a factor of 102 to 103 in response to the evolution of paleosea-surface conditions since the last glacial maximum. Correlations are observed between authigenic Cinorg, 230Th, coccoliths, and 13C content (left-coiling or sinistral Neogloboquadrina pachyderma), and also between authigenic Corg, dinocysts, uranium, and sulfur. Relative Cinorg/Corg burial rates in the deep sediments (> 3000 m) allow us to calculate a net CO2 production in the basin. The net CO2 flux was slightly negative between ~ 20 and ~ 15 ka BP. It reached a first maximum at about 9 ka BP (~ 30 μmol∙cm−2∙a−1 CO2) followed by a decrease at ~ 8 ka BP (~ 20 μmol∙cm−2∙a−1). Since about 7 ka BP, it stabilized at ~ 35 μmol∙cm−2∙a−1. The minimum observed at about 8 ka BP corresponds to a significant rate of Corg burial accompanied with a maximum flux of redox-sensitive indicators (uranium, sulfur). This event does not correspond to any change in sea-surface temperature or salinity, nor in deep circulation, but may be related to the reorganization of the atmospheric circulation during a major breakup stage of the Laurentide ice sheet. The close correlation between the change in CO2 production in the Labrador Sea with variations of atmospheric CO2 concentrations during the last 20 ka BP suggests that the production of biogenic carbonates in subpolar basins plays a role in the global carbon cycle on the scale of glacial–interglacial climate changes.
28
des Abbayes, Hervé, et Jean-Yves Salaün. « Ligand acyle et ligand alkoxycarbonyle : couplage carbone-carbone ou isomérie cycle-chaîne sur l’exemple des complexes octaédriques du fer du type cis-Fe{[C(O)]xR} {[C(O)]yR′}(CO)4 ; x, y = 0,1 ; R ou R′ = CH3, OCH3 ». Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry 2, no 5-6 (mai 1999) : 259–66. http://dx.doi.org/10.1016/s1387-1609(00)88533-3.
Texte intégral
29
Degrieck, Bertrand. « Renaturation du ruisseau de Marcé à Marcé et Seiches-sur-le-Loir (Maine-et-Loire) : reméandrage du cours d’eau et réhumidification de la tourbière ». TSM 11 2023, TSM 11 2023 (20 novembre 2023) : 41–47. http://dx.doi.org/10.36904/tsm/202311041.
Texte intégralRésumé :
Aux confins occidentaux du Bassin parisien et aux portes des basses vallées angevines, la renaturation s’est faite sur le ruisseau de Marcé à Marcé-et-Seiches sur le Loir dans le Maine-et-Loire et a été portée par le Syndicat mixte des basses vallées angevines et de la Romme (le SMBVAR). Le projet visait à restaurer 2,2 km de cours d’eau en tête de bassin versant par remise en fond de vallée, reméandrage et réhausse du fond du lit. Les travaux ont eu pour but de redonner un gabarit naturel au ruisseau, c’est-à-dire moins approfondi et plus étroit, ainsi qu’une sinuosité naturelle méandriforme. L’objectif était de rétablir les fonctionnalités du ruisseau et les habitats liés pour en améliorer la biodiversité. Les travaux ont permis de ralentir le cycle de l’eau pour améliorer la ressource en eau en qualité et en quantité. Plusieurs éléments ont dû être pris en compte pour assurer une efficacité maximale sur divers aspects du site et ainsi maximiser les cobénéfices : prévention des inondations, contexte agricole, usages de l’eau à proximité et plus éloignés du site, préservation d’une tourbière (puits de carbone et alimentation en eau), préservation d’habitats naturels et d’une espèce protégée (l’agrion de Mercure).
30
Nomoto, Hideo, Masao Itoh, William Brown, Jeremy Fetvedt et Iwataro Sato. « ICOPE-15-1176 Cycle and Turbine Development for the Supercritical Carbon Dioxide Allam Cycle ». Proceedings of the International Conference on Power Engineering (ICOPE) 2015.12 (2015) : _ICOPE—15——_ICOPE—15—. http://dx.doi.org/10.1299/jsmeicope.2015.12._icope-15-_112.
Texte intégral
31
Feng, Xuejiao, Hongmin Cui, Zhenming Li, Rongrong Miao et Nanfu Yan. « Scalable Synthesis of Dual-Carbon Enhanced Silicon-Suboxide/Silicon Composite as Anode for Lithium Ion Batteries ». Nano 12, no 07 (juillet 2017) : 1750084. http://dx.doi.org/10.1142/s1793292017500849.
Texte intégralRésumé :
The SiOx/Si composite enhanced by dual-carbon (i.e., multiwall carbon nanotubes and carbon) was fabricated from the micro silicon monoxide (SiO) by the combination of high-energy mechanical milling, spray drying and pyrolysis. The obtained SiOx/Si particles were composed of Si-suboxide and embedded nano-sized Si crystallites. As one of dual-carbons, the multi-walled carbon nanotubes were directly scaffolded of anchoring the SiOx/Si composite particles through spray drying. Another carbon source was directly deposited on the surface of the SiOx/Si by means of the carbonization of phenol–formaldehyde resin. Nano-sized silicon embedded in the Si-suboxide matrix and dual-carbon provided a compromise between the reversible capacity and cycle stability related to the volume change. The obtained SiOx/Si/MWCNT/PC-1 electrode delivered an initial capacity of 936.5[Formula: see text]mAh g[Formula: see text] and the reversible capacity was maintained at 825.9[Formula: see text]mAh g[Formula: see text] with excellent capacity retention of 87.5% on the 200th cycle versus the 6th one (compared with the same current rate). In contrast, although the SiOx/Si presented the higher initial capacity of 1271.4[Formula: see text]mAh g[Formula: see text], its capacity dropped quickly after several cycles and capacity retention was only 25.6% versus the 6th cycle after 100 cycles.
32
Metcalf, S. J., R. E. Critoph et Z. Tamainot-Telto. « Optimal cycle selection in carbon-ammonia adsorption cycles ». International Journal of Refrigeration 35, no 3 (mai 2012) : 571–80. http://dx.doi.org/10.1016/j.ijrefrig.2011.11.006.
Texte intégral
33
Ramos-Vera, W. Hugo, Ivan A. Berg et Georg Fuchs. « Autotrophic Carbon Dioxide Assimilation in Thermoproteales Revisited ». Journal of Bacteriology 191, no 13 (1 mai 2009) : 4286–97. http://dx.doi.org/10.1128/jb.00145-09.
Texte intégralRésumé :
ABSTRACT For Crenarchaea, two new autotrophic carbon fixation cycles were recently described. Sulfolobales use the 3-hydroxypropionate/4-hydroxybutyrate cycle, with acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the carboxylating enzyme. Ignicoccus hospitalis (Desulfurococcales) uses the dicarboxylate/4-hydroxybutyrate cycle, with pyruvate synthase and phosphoenolpyruvate carboxylase being responsible for CO2 fixation. In the two cycles, acetyl-CoA and two inorganic carbons are transformed to succinyl-CoA by different routes, whereas the regeneration of acetyl-CoA from succinyl-CoA proceeds via the same route. Thermoproteales would be an exception to this unifying concept, since for Thermoproteus neutrophilus, the reductive citric acid cycle was proposed as a carbon fixation mechanism. Here, evidence is presented for the operation of the dicarboxylate/4-hydroxybutyrate cycle in this archaeon. All required enzyme activities were detected in large amounts. The key enzymes of the cycle were strongly upregulated under autotrophic growth conditions, indicating their involvement in autotrophic CO2 fixation. The corresponding genes were identified in the genome. 14C-labeled 4-hydroxybutyrate was incorporated into the central building blocks in accordance with the key position of this compound in the cycle. Moreover, the results of previous 13C-labeling studies, which could be reconciled with a reductive citric acid cycle only when some assumptions were made, were perfectly in line with the new proposal. We conclude that the dicarboxylate/4-hydroxybutyrate cycle is operating in CO2 fixation in the strict anaerobic Thermoproteales as well as in Desulfurococcales.
34
Rumyantsev, A. M., et B. I. Zhelnin. « Lithiated iron phosphate for commercial lithium-ion batteries ». Electrochemical Energetics 10, no 1 (2010) : 19–22. http://dx.doi.org/10.18500/1608-4039-2010-10-1-19-22.
Texte intégralRésumé :
Behavior of PH/P1 lithiated iron phosphate (Phostech Lithium Inc, Canada) used as positive electrode material for Li-ion battery with LiPF6-based electrolyte was investigated. Specific capacity of the material reached 130 mA·h/g at a rate of 0.5С and 20°C, 105 mA·h/g (1С) and 95 mA·h/g (2.1C). Cell capacity increased by 20% during first 50 cycles and minor capacity fade at a rate of 0.04% per cycle is observed after 300 cycle when cycled at 2C rate versus carbon negative electrode (CMS, PRC).
35
Wang, Liyong, Tiantian Liu, Shengsheng Ji, Shiwen Yang, Huiqi Wang et Jinhua Yang. « Electrochemical Properties of Carbon Nanobeads and Mesophase-Pitch-Based Graphite Fibers as Anodes for Rechargeable Lithium-Ion Batteries ». Coatings 13, no 10 (24 septembre 2023) : 1671. http://dx.doi.org/10.3390/coatings13101671.
Texte intégralRésumé :
Various strategies have been devised to enhance the specific capacity (over 372 mA h g−1) and the cycle life of pure carbon-based anode materials for lithium-ion batteries (LIBs). Herein, we have prepared carbon nanobeads (CNBs) with inner onion-like carbon layer structures using chemical vapor deposition. Additionally, mesophase-pitch-based graphite fibers (MPGFs) were fabricated via the melt spinning method. MPGFs had a reversible capacity of 328.2 mA h g−1 with a steady Coulombic efficiency after 105 cycles (at 0.05 mA g−1). When cycled at 0.2 A g−1, the CNBs kept a reversible capacity of 586.2 mA h g−1 after 256 cycles with stable Coulombic efficiency. The onion-like carbon layer structures of CNBs were beneficial to the storage of lithium ions. In this work, CNBs were fabricated with inner onion-like carbon layer structures to enhance the electrochemical performance of LIBs.
36
Girnik, Ilya, Alexandra Grekova, Larisa Gordeeva et Yuri Aristov. « Activated Carbons as Methanol Adsorbents for a New Cycle “Heat from Cold” ». Fibers 8, no 8 (8 août 2020) : 51. http://dx.doi.org/10.3390/fib8080051.
Texte intégralRésumé :
Activated carbons are widely used for sustainable technology of adsorptive transformation and storage of heat. Here, we analyze the applicability of twelve commercial carbons and an innovative carbonaceous composite “LiCl confined to multi-wall carbon nanotubes” (LiCl/MWCNT) for a new cycle “Heat from Cold” (HeCol). It has recently been proposed for amplification of low- temperature ambient heat in cold countries. The analysis is made in terms of the methanol mass exchanged and the useful heat generated per cycle; the latter is the main performance indicator of HeCol cycles. The maximum specific useful heat, reaching 990 and 1750 J/g, can be obtained by using carbon Maxsorb III and the composite, respectively. For these materials, methanol adsorption dynamics under typical HeCol conditions are experimentally studied by the large pressure jump method. Before making this analysis, the fine carbon powder is consolidated by either using a binder or just pressing to obtain larger particles (ca. 2 mm). The methanol desorption from the consolidated samples of Maxsorb III at T = 2 °C is faster than for LiCl/MWCNT, and the maximum (initial) useful power reaches (2.5–4.0) kW/kg sorbent. It is very promising for designing compact HeCol units utilizing the carbon Maxsorb III.
37
Yang, Jian, Zachary Hansen, Maruj Jamal, Kevin Mathew, Guanyi Wang, Jie Xiong, Tiffany Zhou et Qingliu Wu. « Biomass-Derived Carbon for High-Performance Lithium-Sulfur Batteries ». ECS Meeting Abstracts MA2022-02, no 4 (9 octobre 2022) : 543. http://dx.doi.org/10.1149/ma2022-024543mtgabs.
Texte intégralRésumé :
With the advantages of high conductivity and low cost, porous carbons have been considered as the most attractive materials as hosts of sulfur cathode in lithium-sulfur batteries (LSBs). However, LSBs always suffer short cycle life due to the “shuttle effect” of lithium polysulfide species (polysulfides), which are intermediate products during the charge/discharge processes. The weak interaction between carbon and polysulfides results in the dissolution of polysulfides from the cathodes, loss of active material and eventually fast capacity fading. To overcome these drawbacks, we employed a biomass-derived carbon as the host material in sulfur cathodes. Results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen sorption reveals that this biomass-derived product is amorphous carbon and is composed of both large (>10 nm) and small (<5 nm) pores. Using as hosts of cathodes in LSBs, the biomass-derived carbons could deliver a high reversible capacity of > 800 mAh/g and retain >80% of initial capacity after 200 cycles. Especially, the activated carbons exhibited 80% capacity retention after 400 cycles. The promising LSB performance could be ascribed to the unique porous architecture of biomass-derived carbons. The meso/micropores in biomass-derived carbons could provide more sites to anchor sulfur and polysulfides, while macropores provide channels for fast transport of ions. This was corroborated by the results from the electrochemical impedance spectroscopy (EIS), the thermogravimetric analysis (TGA) and absorption measurements.
38
Nakul, F., Akfiny Aimon, D. Suhendra, B. Nuryadin et Ferry Iskandar. « Pengaruh Duty Cycle Microwave pada Sifat Fotoluminesensi Material Carbon Nanodots ». Jurnal Matematika dan Sains 24, no 2 (décembre 2019) : 46–49. http://dx.doi.org/10.5614/jms.2019.24.2.3.
Texte intégralRésumé :
Microwave banyak dimanfaatkan sebagai media pemanas termasuk di bidang sintesis material. Pemanasan melalui microwave memiliki keunggulan dibandingkan pemanas konvensional dikarenakan waktu pemanasan singkat dengan distribusi yang sera-gam. Untuk mempelajari mekanisme transfer energi dari sebuah microwave, diperlukan upaya pengendalian energi gelombang agar suplai energi panas yang diberikan dapat dikontrol dengan baik. Pada penelitian ini, pengontrolan suplai energi dilakukan dengan mengatur duty cycle microwave dengan level yang berbeda selama proses sintesis material carbon nanodots (CNDs). Selanjutnya, sifat fotoluminesensi dari material ini dikarakterisasi dengan spektrofotometer fluoresensi untuk menentukan tingkat intensitas pendaran yang dihasilkan.
39
Wu, Jimmy, Matthew A. Hughes, Neeraj Sharma et Jessica Allen. « Influence of Growth Parameters on the Electrochemical Performance of Electrodeposited Carbons ». Batteries 8, no 8 (29 juillet 2022) : 81. http://dx.doi.org/10.3390/batteries8080081.
Texte intégralRésumé :
Generating useful chemicals from CO2 is driving research into carbon capture and utilization. In this work, hard carbons are electrodeposited on various substrates from molten carbonate melts in CO2 atmospheres. These electrodeposited carbons are subsequently used as anodes in sodium-ion batteries, with preliminary investigations into their performance in potassium-ion batteries. The hard carbons were characterized using X-ray diffraction (XRD) and Raman spectroscopy. Hard carbons grown on graphite substrates produced initial reversible capacities of 405 ± 29 mAh/g and capacity retention of 85.2 ± 1.1% after 50 cycles when cycled at 10 mA/g which are amongst the highest capacities reported for hard carbons to date. This work clearly illustrates that the carbons generated via CO2 mediated electrodeposition are suitable for application in next generation batteries.
40
Álvarez-Gómez, Ainhoa, Jiayin Yuan, Juan P. Fernández-Blázquez, Verónica San-Miguel et María B. Serrano. « Polyacrylonitrile-b-Polystyrene Block Copolymer-Derived Hierarchical Porous Carbon Materials for Supercapacitor ». Polymers 14, no 23 (24 novembre 2022) : 5109. http://dx.doi.org/10.3390/polym14235109.
Texte intégralRésumé :
The use of block copolymers as a sacrificial template has been demonstrated to be a powerful method for obtaining porous carbons as electrode materials in energy storage devices. In this work, a block copolymer of polystyrene and polyacrylonitrile (PS−b−PAN) has been used as a precursor to produce fibers by electrospinning and powdered carbons, showing high carbon yield (~50%) due to a low sacrificial block content (fPS ≈ 0.16). Both materials have been compared structurally (in addition to comparing their electrochemical behavior). The porous carbon fibers showed superior pore formation capability and exhibited a hierarchical porous structure, with small and large mesopores and a relatively high surface area (~492 m2/g) with a considerable quantity of O/N surface content, which translates into outstanding electrochemical performance with excellent cycle stability (close to 100% capacitance retention after 10,000 cycles) and high capacitance value (254 F/g measured at 1 A/g).
41
Bhatia, Muskan, Jyotika Thakur, Shradha Suyal, Ruchika Oniel, Rahul Chakraborty, Shalini Pradhan, Monika Sharma et al. « Allosteric inhibition of MTHFR prevents futile SAM cycling and maintains nucleotide pools in one-carbon metabolism ». Journal of Biological Chemistry 295, no 47 (15 septembre 2020) : 16037–57. http://dx.doi.org/10.1074/jbc.ra120.015129.
Texte intégralRésumé :
Methylenetetrahydrofolate reductase (MTHFR) links the folate cycle to the methionine cycle in one-carbon metabolism. The enzyme is known to be allosterically inhibited by SAM for decades, but the importance of this regulatory control to one-carbon metabolism has never been adequately understood. To shed light on this issue, we exchanged selected amino acid residues in a highly conserved stretch within the regulatory region of yeast MTHFR to create a series of feedback-insensitive, deregulated mutants. These were exploited to investigate the impact of defective allosteric regulation on one-carbon metabolism. We observed a strong growth defect in the presence of methionine. Biochemical and metabolite analysis revealed that both the folate and methionine cycles were affected in these mutants, as was the transsulfuration pathway, leading also to a disruption in redox homeostasis. The major consequences, however, appeared to be in the depletion of nucleotides. 13C isotope labeling and metabolic studies revealed that the deregulated MTHFR cells undergo continuous transmethylation of homocysteine by methyltetrahydrofolate (CH3THF) to form methionine. This reaction also drives SAM formation and further depletes ATP reserves. SAM was then cycled back to methionine, leading to futile cycles of SAM synthesis and recycling and explaining the necessity for MTHFR to be regulated by SAM. The study has yielded valuable new insights into the regulation of one-carbon metabolism, and the mutants appear as powerful new tools to further dissect out the intersection of one-carbon metabolism with various pathways both in yeasts and in humans.
42
Kocken, Ilja J., Margot J. Cramwinckel, Richard E. Zeebe, Jack J. Middelburg et Appy Sluijs. « The 405 kyr and 2.4 Myr eccentricity components in Cenozoic carbon isotope records ». Climate of the Past 15, no 1 (16 janvier 2019) : 91–104. http://dx.doi.org/10.5194/cp-15-91-2019.
Texte intégralRésumé :
Abstract. Cenozoic stable carbon (δ13C) and oxygen (δ18O) isotope ratios of deep-sea foraminiferal calcite co-vary with the 405 kyr eccentricity cycle, suggesting a link between orbital forcing, the climate system, and the carbon cycle. Variations in δ18O are partly forced by ice-volume changes that have mostly occurred since the Oligocene. The cyclic δ13C–δ18O co-variation is found in both ice-free and glaciated climate states, however. Consequently, there should be a mechanism that forces the δ13C cycles independently of ice dynamics. In search of this mechanism, we simulate the response of several key components of the carbon cycle to orbital forcing in the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir model (LOSCAR). We force the model by changing the burial of organic carbon in the ocean with various astronomical solutions and noise and study the response of the main carbon cycle tracers. Consistent with previous work, the simulations reveal that low-frequency oscillations in the forcing are preferentially amplified relative to higher frequencies. However, while oceanic δ13C mainly varies with a 405 kyr period in the model, the dynamics of dissolved inorganic carbon in the oceans and of atmospheric CO2 are dominated by the 2.4 Myr cycle of eccentricity. This implies that the total ocean and atmosphere carbon inventory is strongly influenced by carbon cycle variability that exceeds the timescale of the 405 kyr period (such as silicate weathering). To test the applicability of the model results, we assemble a long (∼22 Myr) δ13C and δ18O composite record spanning the Eocene to Miocene (34–12 Ma) and perform spectral analysis to assess the presence of the 2.4 Myr cycle. We find that, while the 2.4 Myr cycle appears to be overshadowed by long-term changes in the composite record, it is present as an amplitude modulator of the 405 and 100 kyr eccentricity cycles.
43
Kanaujiya, Amit. « Thermodynamic study of solarized supercritical carbon dioxide cycle ». International Journal of Advance Research and Innovation 8, no 4 (2020) : 148–53. http://dx.doi.org/10.51976/ijari.842024.
Texte intégralRésumé :
The supercritical carbon dioxide cycle run on the utilization of carbon dioxide uses emissions from fossil fuel-fired power plants. In this study, the supercritical carbon dioxide cycle is powered by solar energy using heliostat fields. The operating range of supercritical carbon dioxide cycle permits for the integration of low-temperature cycles for effective utilization of the heat remaining unutilized in it. This paper considers the supercritical carbon dioxide cycle for its energy analysis. It aims for the optimal utilization of heat available with the exhaust from the sCO2 cycle. Results obtained based on parametric variation have been presented and analyzed here. At the turbine inlet pressure of 290 bar, the turbine inlet temperature of 700oC in sCO2 cycle and cycle efficiency is obtained as 16.56 % and specific work output is 174.6 KJ/kg of sCO2.
44
Green, Michael H. « Are Fatty Acids Gluconeogenic Precursors ? » Journal of Nutrition 150, no 9 (11 juillet 2020) : 2235–38. http://dx.doi.org/10.1093/jn/nxaa165.
Texte intégralRésumé :
ABSTRACT It is widely accepted that the tricarboxylic acid (TCA) cycle is a critical partner for gluconeogenesis (GNG) in hepatocytes. Although researchers in the 1950s showed, using radiolabeled long-chain fatty acids, that acetate derived from fatty acid β-oxidation contributes carbon to glucose, fatty acids are not included on lists of gluconeogenic precursors in many textbooks of biochemistry and nutritional biochemistry. Here, by following the flow of carbon atoms through the mitochondrial TCA cycle and into cytosolic GNG, it is shown that carbons in acetyl-CoA derived from fatty acid β-oxidation will be found in glucose. Specifically, it is evident that, after the condensation of acetyl-CoA and oxaloacetate (OAA) to make citrate at the start of the TCA cycle, the 2 carbons lost from the cycle as carbon dioxide come from OAA, not acetyl-CoA. Carbons from acetyl-CoA are retained as the cycle progresses toward malate, and when malate exits the mitochondrion for GNG, carbons that originated in acetyl-CoA and OAA are found to contribute equally to glucose. With influx of other critical precursors into the TCA cycle and efflux of malate into the cytosol for GNG, the TCA cycle is in balance. During fasting-induced GNG, there is a net gain of glucose in glucogenic cells; however, the fact that there is no net gain in the TCA cycle is irrelevant as far as precursors are concerned. Given the physiological importance of fat as a source of reserve energy, and knowing that some cell types rely on glucose as their primary supplier of energy, a role for fatty acids in glucose production aligns both with intuition and with evidence provided by a careful look at the biochemistry and older isotope studies. Hopefully, subsequent editions of textbooks will list fatty acids among the gluconeogenic precursors.
45
Mokhati, Asma, Oumessaâd Benturki, Asma Benturki, Radia Fennouh, Zoubida Kecira, Maria Bernardo, Inês Matos et al. « Conversion of Argan Nutshells into Novel Porous Carbons in the Scope of Circular Economy : Adsorption Performance of Emerging Contaminants ». Applied Sciences 12, no 15 (28 juillet 2022) : 7607. http://dx.doi.org/10.3390/app12157607.
Texte intégralRésumé :
The present work proposes an experimental strategy to prepare argan nutshell-derived porous carbons using potassium hydroxide (KOH). Several experimental parameters of the activation process were evaluated (temperature, impregnation ratio, and activation time), and an optimized carbon (ACK) was obtained. The surface properties of the ACK sample were determined, and the porous carbon was applied as an adsorbent of diclofenac (DCF) and paroxetine (PARX). A commercial carbon (CC) was used as a benchmark. The ACK porous carbon presented a higher surface area and micropore volume (1624 m2 g−1 and 0.40 cm3 g−1, respectively) than CC carbon (1030 m2 g−1 and 0.30 cm3 g−1, respectively), but the maximum adsorption capacities of DCF (214–217 mg g−1) and PARX (260–275 mg g−1) were comparable among the two carbons. Besides π-π interactions, H-bonds with the electronegative atoms of the adsorbate molecules and the electropositive H of the oxygen functional groups were appointed as the most probable mechanisms for adsorption onto ACK porous carbon. The electrostatic attraction was also considered, particularly for DCF with CC carbon. The pore size might have also been critical, since CC carbon presented more supermicropores (0.7–2 nm), which are usually more favorable toward the adsorption of pharmaceutical molecules. The reusability of the ACK carbon was tested up to four cycles of adsorption–desorption by using ultrasonic washing with water. The results indicated that no more than one cycle of use of ACK should be performed.
46
Alrebei, Odi Fawwaz, Philip Bowen et Agustin Valera Medina. « Parametric Study of Various Thermodynamic Cycles for the Use of Unconventional Blends ». Energies 13, no 18 (7 septembre 2020) : 4656. http://dx.doi.org/10.3390/en13184656.
Texte intégralRésumé :
This paper aims to conduct a parametric study for five gas turbine cycles (namely, simple, heat exchanged, free turbine and simple cycle, evaporative, and humidified) using a CO2-argon-steam-oxyfuel (CARSOXY) mixture as a working fluid to identify their optimal working conditions with respect to cycle efficiency and specific work output. The performance of the five cycles using CARSOXY is estimated for wet and dry compression, and a cycle is suggested for each range of working conditions. The results of this paper are based on MATLAB codes, which have been developed to conduct the cycle analysis for CARSOXY gas turbines, assuming a stoichiometric condition with an equivalence ratio of 1.0. Analyses are based on the higher heating value (HHV) of methane as fuel. This paper also identifies domains of operating conditions for each cycle, where the efficiency of CARSOXY cycles can be increased by up to 12% compared to air-driven cycles. The CARSOXY heat exchanged cycle has the highest efficiency among the other CARSOXY cycles in the compressor pressure ratio domain of 2–3 and 6–10, whereas, at 3–6, the humidified cycle has the highest efficiency. The evaporative cycle has intermediate efficiency values, while the simple cycle and the free turbine-simple cycle have the lowest efficiencies amongst the five cycles. Additionally, a 10% increase in the cycle efficiency can be theoretically achieved by using the newly suggested CARSOXY blend that has the molar fractions of 47% argon, 10% carbon dioxide, 10% H2O, and 33% oxyfuel at low compressor inlet temperatures, thus theoretically enabling the use of carbon capture technologies.
47
Ramirez Zamora, R. M., et R. Seux. « Oxydation du diuron et identification de quelques sous-produits de la réaction ». Revue des sciences de l'eau 12, no 3 (12 avril 2005) : 545–60. http://dx.doi.org/10.7202/705365ar.
Texte intégralRésumé :
Ce travail étudie la dégradation en milieu aqueux de l'herbicide diuron (N-(3,4 dichlorophényl)-N'-(diméthyl)-urée) par oxydation radicalaire. Des solutions de diuron (0,01 mg L-1 et 5 mg L-1) tamponnées à pH=7 ont été traitées par l'ozone et par le couple peroxyde d'hydrogène-ozone (0,35 mole/mole). Les doses d´ozone appliquées ont été de 2 mg O3 L-1 pour la solution de diuron à 0,01 mg L-1 et 6 mg O3 L-1 pour la solution à 5 mg L-1. Les temps de réaction utilisés ont été de 30 min pour la forte concentration en diuron et de 8 min pour la concentration faible. L'identification de quelques sous-produits par chromatographie gazeuse couplée à la spectrométrie de masse (CG-SM) a été réalisée sur les extraits des solutions traitées. Les résultats montrent que lors de l'oxydation, le cycle aromatique est conservé pour trois sous-produits : la N-(3,4 dichlorophényl)-N-(méthyl)-urée (DCPMU), la N-(3,4 dichlorophényl)-N-(méthyl)-urée (DCPU) et la 3,4 dichloroaniline (DCA). Ces composés ont été identifiés à la fois dans les solutions de diuron traitées par l'ozone et dans celles traitées par le couple ozone-peroxyde d'hydrogène. La quantification du diuron et des sous-produits identifiés a été faite par chromatographie liquide à haute performance (HPLC). Le pourcentage d'oxydation du diuron par l'ozone et le couple ozone-peroxyde d'hydrogène est élevé (respectivement 80% et 90%), pour les conditions expérimentales : Co =5 mg L-1 ; temps de réaction=30 min et ozone appliqué=6 mg L-1. Le dosage du carbone organique total (COT) a mis en évidence une minéralisation partielle de cet herbicide (" 50%). Le bilan massique de la réaction montre que le DCPMU est un des principaux sous-produits d'oxydation du diuron (de 5 à 7% de la quantité initiale de diuron).
48
Jia, Zheng, Dao Qing Liu et Si Yuan Yang. « Electrochemical Insight into Cycle Stability of Organic Electrolyte Supercapacitors ». Advanced Materials Research 347-353 (octobre 2011) : 467–71. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.467.
Texte intégralRésumé :
Two types of activated carbons were produced by chemical activation respectively with and without pre-carbonization procedure, and were used in organic electrolyte supercapacitors. Galvanostatic charge and discharge results show that voltage upper limit and activated carbon type obviously influence the cycle stability of the capacitors. And cyclic voltammograms reveal the better capacitive behavior and cycle stability of the activated carbon produced with carbonization procedure implying the correlation between these two factors. While Nyquist plots disclose the tendency of equivalent circuit component parameters and electrode processes with cycling.
49
Spring, Aaron, István Dunkl, Hongmei Li, Victor Brovkin et Tatiana Ilyina. « Trivial improvements in predictive skill due to direct reconstruction of the global carbon cycle ». Earth System Dynamics 12, no 4 (15 novembre 2021) : 1139–67. http://dx.doi.org/10.5194/esd-12-1139-2021.
Texte intégralRésumé :
Abstract. State-of-the art climate prediction systems have recently included a carbon component. While physical-state variables are assimilated in reconstruction simulations, land and ocean biogeochemical state variables adjust to the state acquired through this assimilation indirectly instead of being assimilated themselves. In the absence of comprehensive biogeochemical reanalysis products, such an approach is pragmatic. Here we evaluate a potential advantage of having perfect carbon cycle observational products to be used for direct carbon cycle reconstruction. Within an idealized perfect-model framework, we reconstruct a 50-year target period from a control simulation. We nudge variables from this target onto arbitrary initial conditions, mimicking an assimilation simulation generating initial conditions for hindcast experiments of prediction systems. Interested in the ability to reconstruct global atmospheric CO2, we focus on the global carbon cycle reconstruction performance and predictive skill. We find that indirect carbon cycle reconstruction through physical fields reproduces the target variations. While reproducing the large-scale variations, nudging introduces systematic regional biases in the physical-state variables to which biogeochemical cycles react very sensitively. Initial conditions in the oceanic carbon cycle are sufficiently well reconstructed indirectly. Direct reconstruction slightly improves initial conditions. Indirect reconstruction of global terrestrial carbon cycle initial conditions are also sufficiently well reconstructed by the physics reconstruction alone. Direct reconstruction negligibly improves air–land CO2 flux. Atmospheric CO2 is indirectly very well reconstructed. Direct reconstruction of the marine and terrestrial carbon cycles slightly improves reconstruction while establishing persistent biases. We find improvements in global carbon cycle predictive skill from direct reconstruction compared to indirect reconstruction. After correcting for mean bias, indirect and direct reconstruction both predict the target similarly well and only moderately worse than perfect initialization after the first lead year. Our perfect-model study shows that indirect carbon cycle reconstruction yields satisfying initial conditions for global CO2 flux and atmospheric CO2. Direct carbon cycle reconstruction adds little improvement to the global carbon cycle because imperfect reconstruction of the physical climate state impedes better biogeochemical reconstruction. These minor improvements in initial conditions yield little improvement in initialized perfect-model predictive skill. We label these minor improvements due to direct carbon cycle reconstruction “trivial”, as mean bias reduction yields similar improvements. As reconstruction biases in real-world prediction systems are likely stronger, our results add confidence to the current practice of indirect reconstruction in carbon cycle prediction systems.
50
Kindra, Vladimir, Igor Maksimov, Daniil Patorkin, Andrey Rogalev et Nikolay Rogalev. « Thermodynamic Analysis and Optimization of Binary CO2-Organic Rankine Power Cycles for Small Modular Reactors ». Energies 17, no 10 (15 mai 2024) : 2377. http://dx.doi.org/10.3390/en17102377.
Texte intégralRésumé :
Small nuclear power plants are a promising direction of research for the development of carbon-free energy in isolated power systems and in remote regions with undeveloped infrastructure. Improving the efficiency of power units integrated with small modular reactors will improve the prospects for the commercialization of such projects. Power cycles based on supercritical carbon dioxide are an effective solution for nuclear power plants that use reactor facilities with an initial coolant temperature above 550 °C. However, the presence of low temperature rejected heat sources in closed Bryton cycles indicates a potential for energy saving. This paper presents a comprehensive thermodynamic analysis of the integration of an additional low-temperature organic Rankine cycle for heat recovery to supercritical carbon dioxide cycles. A scheme for sequential heat recovery from several sources in S-CO2 cycles is proposed. It was found that the use of R134a improved the power of the low-temperature circuit. It was revealed that in the S-CO2 Brayton cycle with a recuperator, the ORC add-on increased the net efficiency by an average of 2.98%, and in the recompression cycle by 1.7–2.2%. With sequential heat recovery in the recuperative cycle from the intercooling of the compressor and the main cooler, the increase in efficiency from the ORC superstructure will be 1.8%.