The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample tempera...The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample temperature is finely controlled.We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05℃and impose temperature ramps down to 0.002℃/min,necessary to characterize the largest pore sizes.The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here.For porous materials made of paramagnetic minerals such as lithium-iron phosphate(LiFePO_(4),LFP)or nickel-manganese-cobalt oxides(NMC)and saturated with octamethylcyclotetrasiloxane(OMCTS),the T_(2)relaxation times are very short such as protons from the liquid and frozen phases cannot be separated.Hence the usual cryoporometry experiment cannot be performed.Instead,we propose to use the T_(1)contrast to separate these phases.The method is studied in detail along with some temperature effects linked with the T_(1)variation of the bulk frozen OMCTS.We show an example on two cathode materials part of industrial battery product.展开更多
With the European Union(EU)introducing the Carbon Border Adjustment Mechanism(CBAM),accurately forecasting EU carbon price is crucial for exporters to estimate export costs,plan low-carbon strategies,and mitigate trad...With the European Union(EU)introducing the Carbon Border Adjustment Mechanism(CBAM),accurately forecasting EU carbon price is crucial for exporters to estimate export costs,plan low-carbon strategies,and mitigate trade risks.In the petroleum sector,carbon pricing directly influences upstream investment returns and carbon intensity targets,thereby closely linking emissions markets with fossil energy strategies.Existing models often fail to fully capture the nonlinear,non-stationary nature of carbon prices and their dependence on external factors.This study proposes a novel hybrid framework that combines improved complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN)with gated recurrent unit-convolutional neural network-long short-term memory network-Bayesian optimization(GRU-CNN-LSTM-BO).Empirical results based on the EU emissions trading system(ETS)market demonstrate that the proposed model significantly improves forecasting accuracy.Among all experiments,the proposed GRU-CNN-LSTM-BO framework achieves the best performance,yielding the lowest MAE(1.3872),RMSE(1.7038),MAPE(0.0166),and MSPE(0.0004),as well as the highest R2(0.9400).Compared to all benchmark models,the GRU-CNN-LSTM-BO model achieves reductions in MAE and RMSE ranging from 5.38%to 63.65%and 8.97%to 64.41%,respectively.To further validate the generalization ability and predictive performance of the proposed model,it is also applied to China's ETS.The results show that the GRU-CNN-LSTM-BO model also performs very well in China's ETS.展开更多
Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-par...Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-particle and particle-surface).They have important implications for engineering applications involving the reinjection of a fluidinto a medium,such as geothermal energy.The investigation of permeability stability is critical to ensure the sustainability of activities.This work aims to study the clogging mechanisms in a rock-like porous medium using a microfluidicdevice.The pore-throat network distributions reveal that the micromodel geometry mimics real rock samples.The transport of a monodispersed suspension is studied at different concentrations.Image analysis,velocity fieldmodeling,and pressure drop measurement are used to assess preferential clogging sites and porous medium permeability reduction,respectively.Experiments have shown that retention sites are located around preferential flow paths with relatively high flow velocities.When clogged,the pore thresholds are the deposition zones that lead to a reduction in permeability.However,pore bodies may also constitute deposition zones.Interestingly,as the concentration of the suspension increases,the kinetics of the permeability reduction are delayed,and the clogging mechanisms,as well as the type of deposit,evolve.Finally,at very high concentrations,the effects of hydrodynamic stripping are more important.These observations emphasize the role of the porous medium geometry in colloidal transport and deposition and thus permeability reduction.展开更多
Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the eval...A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the evaluation of fluxes at the in- terface between neighboring elements, with a Nth-order leap-frog time scheme. More- over, the interpolation degree is defined at the element level and the mesh is refined locally in a non-conforming way resulting in arbitrary level hanging nodes. The method is proved to be stable under some CFL-like condition on the time step. The convergence of the semi-discrete approximation to Maxwelrs equations is established rigorously and bounds on the global divergence error are provided. Numerical experiments with high- order elements show the potential of the method.展开更多
Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for...Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for the production ofcellulolytic enzymes is the fungus Trichoderma reesei, mostly due to its high secretion capacity. Unfortunately, this fungus secretes very low concentrations of β-glucosidase, thereby often requiring β-glucosidase supplementation for complete cellulose hydrolysis. It is especially important to have sufficient quantities of β-glucosidase in order to prevent inhibition of cellobiohydrolases by cellobiose. In order to optimize the produced cocktail, a more efficient β-glucosidase was cloned into T. reesei CL847 strain. The new strain, called CL847 TR3002, secretes the evolved β-glucosidase and was tested for cellulase production in laboratory-scale reactors. Its growth kinetics and cellulase production were characterized using fed-batch and chemostat modes under various culture conditions. The cellulase activities of the evolved strain were compared with activities of the parent strain. In addition, hydrolysis of a steam exploded wheat straw was performed at three different enzyme-loading levels （5 mg/g, 10 mg/g and 20 mg/g of dry matter） and a new kinetic model was developed.展开更多
Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles...Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles （NP＇s） which were distributed in an organic matrix. Au atoms deposited onto a copper phthalocyanine （CuPc） surface diffuse into the organic matrix and self-assemble in well defined NP＇s with metallic properties. No formation of a continuous metallic Au film on top of the CuPc film is observed up to nominal coverages as large as 130 A.展开更多
Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operatio...Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operational conditions for ＂spray-drying＂ processes, in order to obtain the powder of mango pulp by means of a rotational central compounded planning, and also at carrying out the physicochemical characterization of both the integral mango pulp and the powder obtained from the operational conditions mentioned above. Both integral mango pulp and powder were analyzed as for the following physicochemical characteristics： humidity, pH, titratable acidity, soluble solids （~Brix）, vitamin C and color--through parameters L＊, a＊, b＊ and h0, Chrome （C＊） and color difference （AEL＊a＊b＊）. The experimental planning used presented significant differences at 5% of probability, showing that the model was adjusted to the data in accordance to F test, thus being possible to determine the best process conditions. In addition, the average results of the physicochemical parameters pointed out that the pulp used was in accordance with the patterns established by the quality and identity patterns for mango pulp. Moreover, it showed that the powder obtained had good physicochemical quality.展开更多
The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used...The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.展开更多
This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest repor...This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest reported by the scientific literature regarding the late effects in skeletal muscle resulting from exposure to ionizing radiation. Original and experimental papers mainly containing the key expressions “ionizing radiation” and “effects on skeletal muscle” were searched in computerized databases, and published in any language. Only 33 papers matched the search criteria. Analyzing the investigated radioinduced biological effects in those contributions, four topics were identified as being of major interest: 1) alterations in cellular metabolism and protein degradation;2) repercussions on satellite cells;3) formation of fibrosis and muscle atrophy;4) tissue regeneration. It was verified that no study evaluated possible late effects related to either morphology or properties of skeletal muscles after an exposure to ionizing radiation. Several aspects do not make possible a successful replication;all experiments of eligible group of articles are discussed, such as, lack of raw data, use of no sound methodology and inappropriate statistical technique. Briefly, the subject of this review is an open field of research.展开更多
The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national ...The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national specificities. HyFrance3 is a new project that focuses on the economic competitiveness of different steps of the hydrogen chain, from the production to end usage, at the time horizon of 2030 in France. The project is coordinated by CEA with the other partners being： ADEME （co-funding）, AFH2, CNRS, IFP, Air Liquide, EdF, GdF Suez, TOTAL, ALPHEA. The project is divided into 4 sub-projects, that address present and future French hydrogen industrial markets for chemical ＆ refinery uses, the analysis of the interplay between wind energy production and storage of hydrogen for different automotive requirements （refuelling stations, BtL plants, H2/NG mix）, massive hydrogen storage to balance various offer and demand characteristics, and the supply network （pipeline option competitiveness vs. trucked in supply） to distribute hydrogen in a French region for automotive applications. Technical and economical issues, as well as GHG emissions, are addressed.展开更多
The utilization of photocatalysis for CO_(2) conversion into solar fuels holds significant promise for advancing clean energy solutions;however,there are still many uncertainties regarding the surface mechanisms of th...The utilization of photocatalysis for CO_(2) conversion into solar fuels holds significant promise for advancing clean energy solutions;however,there are still many uncertainties regarding the surface mechanisms of the reaction,even for the most commonly studied TiO_(2)-based photocatalytic systems.Of special relevance is the origin of photoconverted products and the role played by adventitious carbon species on the photocatalyst surface,whose nature and origin lack unambiguous identification to date.In this study,we investigated the dynamic nature of vapor-phase photocatalytic CO_(2) reduction using a benchmark Pt/TiO_(2) photocatalyst.To identify carbon species on the photocatalyst surface,we reported a comprehensive analytical approach involving X-ray photoelectron spectroscopy (XPS),thermogravimetric analysis (TGA),and operando Fourier-transform infrared (FTIR) spectroscopy during the activation and photocatalytic reduction of CO_(2).Through this multi-technique approach,we were able to differentiate initial carbonaceous surface species and identify active intermediates during reactions.Upon irradiation,carbon species in the form of carboxylates get involved in reactions with photocatalytically activated surface adsorbed water and can contribute to 40% of methane yields in the first few minutes of irradiation,therefore hindering a reliable quantification of CO_(2) conversion levels.This was confirmed by exposure of the catalyst to light and water vapor during ten irradiation cycles,which significantly reduced the amount of methane and C-species on the catalyst surface.Transient activity was identified as the dominant factor driving methane production.Moreover,reactivation of the catalyst can be achieved through periodic irradiation conditions,leading to a remarkable 60% increase in methane production yields during 180 minutes of irradiation.These findings shed light on the mechanisms occurring on the photocatalyst surface upon light/dark transition steps and demonstrate the potential for enhancing CO_(2) photoreduction performance through periodic irradiation strategies.展开更多
Using a prototypical family of hierarchical zeolites,we show how adsorption-based characterization can be extended to provide morphological and topological assessment beyond state-of-the-art tools.The well-controlled ...Using a prototypical family of hierarchical zeolites,we show how adsorption-based characterization can be extended to provide morphological and topological assessment beyond state-of-the-art tools.The well-controlled materials under study consist of submicron-sized zeolite crystals(silicalite-1)that exhibit large nanoporous cavities in addition to their intrinsic microporosity.Such zeolites nanoboxes can be prepared with a single large cavity,with several independent cavities or with several interconnected cavities depending on synthesis conditions.It is shown that analysis of the adsorption/desorption branches using the Derjaguin model allows determining the cavity size distributions in these materials but also the fraction of pores directly connected to the external surface for each cavity size.Moreover,using the independent domain theory,we illustrate how scanning the capillary hysteresis provides a means to determine whether pores behave independently from each other or are connected to each other.All our findings are found to be consistent with additional electron microscopy data including electron tomography data.展开更多
As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion c...As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion characteristics,reactivity,and exhaust gas compositions compared to conventional fuels,raising questions about the suitability of lubricants in engines operating with them.The impact of ammonia,hydrogen,and their blends on lubricants in internal combustion engines is a relatively new topic,with few reference studies available.However,degradation processes of lubricants have been studied in the context of hydrocarbon fuels,and in compressors using ammonia as a refrigerant,for example.This work presents a review of the literature on engine oil degradation phenomena in relation to ammonia and hydrogen combustion characteristics.In particular,it highlights the current state of knowledge regarding compatibility with unburnt gases,elevated nitrogen oxide levels,and water.Additionally,it summarizes the latest insights into the contribution of lubricants to pollutant emissions.展开更多
文摘The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample temperature is finely controlled.We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05℃and impose temperature ramps down to 0.002℃/min,necessary to characterize the largest pore sizes.The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here.For porous materials made of paramagnetic minerals such as lithium-iron phosphate(LiFePO_(4),LFP)or nickel-manganese-cobalt oxides(NMC)and saturated with octamethylcyclotetrasiloxane(OMCTS),the T_(2)relaxation times are very short such as protons from the liquid and frozen phases cannot be separated.Hence the usual cryoporometry experiment cannot be performed.Instead,we propose to use the T_(1)contrast to separate these phases.The method is studied in detail along with some temperature effects linked with the T_(1)variation of the bulk frozen OMCTS.We show an example on two cathode materials part of industrial battery product.
基金supported by the National Natural Science Foundation of China(Grant No.72401011).
文摘With the European Union(EU)introducing the Carbon Border Adjustment Mechanism(CBAM),accurately forecasting EU carbon price is crucial for exporters to estimate export costs,plan low-carbon strategies,and mitigate trade risks.In the petroleum sector,carbon pricing directly influences upstream investment returns and carbon intensity targets,thereby closely linking emissions markets with fossil energy strategies.Existing models often fail to fully capture the nonlinear,non-stationary nature of carbon prices and their dependence on external factors.This study proposes a novel hybrid framework that combines improved complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN)with gated recurrent unit-convolutional neural network-long short-term memory network-Bayesian optimization(GRU-CNN-LSTM-BO).Empirical results based on the EU emissions trading system(ETS)market demonstrate that the proposed model significantly improves forecasting accuracy.Among all experiments,the proposed GRU-CNN-LSTM-BO framework achieves the best performance,yielding the lowest MAE(1.3872),RMSE(1.7038),MAPE(0.0166),and MSPE(0.0004),as well as the highest R2(0.9400).Compared to all benchmark models,the GRU-CNN-LSTM-BO model achieves reductions in MAE and RMSE ranging from 5.38%to 63.65%and 8.97%to 64.41%,respectively.To further validate the generalization ability and predictive performance of the proposed model,it is also applied to China's ETS.The results show that the GRU-CNN-LSTM-BO model also performs very well in China's ETS.
文摘Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-particle and particle-surface).They have important implications for engineering applications involving the reinjection of a fluidinto a medium,such as geothermal energy.The investigation of permeability stability is critical to ensure the sustainability of activities.This work aims to study the clogging mechanisms in a rock-like porous medium using a microfluidicdevice.The pore-throat network distributions reveal that the micromodel geometry mimics real rock samples.The transport of a monodispersed suspension is studied at different concentrations.Image analysis,velocity fieldmodeling,and pressure drop measurement are used to assess preferential clogging sites and porous medium permeability reduction,respectively.Experiments have shown that retention sites are located around preferential flow paths with relatively high flow velocities.When clogged,the pore thresholds are the deposition zones that lead to a reduction in permeability.However,pore bodies may also constitute deposition zones.Interestingly,as the concentration of the suspension increases,the kinetics of the permeability reduction are delayed,and the clogging mechanisms,as well as the type of deposit,evolve.Finally,at very high concentrations,the effects of hydrodynamic stripping are more important.These observations emphasize the role of the porous medium geometry in colloidal transport and deposition and thus permeability reduction.
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
基金supported by a grant from the French National Ministry of Education and Research(MENSR,19755-2005)
文摘A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the evaluation of fluxes at the in- terface between neighboring elements, with a Nth-order leap-frog time scheme. More- over, the interpolation degree is defined at the element level and the mesh is refined locally in a non-conforming way resulting in arbitrary level hanging nodes. The method is proved to be stable under some CFL-like condition on the time step. The convergence of the semi-discrete approximation to Maxwelrs equations is established rigorously and bounds on the global divergence error are provided. Numerical experiments with high- order elements show the potential of the method.
文摘Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for the production ofcellulolytic enzymes is the fungus Trichoderma reesei, mostly due to its high secretion capacity. Unfortunately, this fungus secretes very low concentrations of β-glucosidase, thereby often requiring β-glucosidase supplementation for complete cellulose hydrolysis. It is especially important to have sufficient quantities of β-glucosidase in order to prevent inhibition of cellobiohydrolases by cellobiose. In order to optimize the produced cocktail, a more efficient β-glucosidase was cloned into T. reesei CL847 strain. The new strain, called CL847 TR3002, secretes the evolved β-glucosidase and was tested for cellulase production in laboratory-scale reactors. Its growth kinetics and cellulase production were characterized using fed-batch and chemostat modes under various culture conditions. The cellulase activities of the evolved strain were compared with activities of the parent strain. In addition, hydrolysis of a steam exploded wheat straw was performed at three different enzyme-loading levels （5 mg/g, 10 mg/g and 20 mg/g of dry matter） and a new kinetic model was developed.
文摘Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles （NP＇s） which were distributed in an organic matrix. Au atoms deposited onto a copper phthalocyanine （CuPc） surface diffuse into the organic matrix and self-assemble in well defined NP＇s with metallic properties. No formation of a continuous metallic Au film on top of the CuPc film is observed up to nominal coverages as large as 130 A.
文摘Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operational conditions for ＂spray-drying＂ processes, in order to obtain the powder of mango pulp by means of a rotational central compounded planning, and also at carrying out the physicochemical characterization of both the integral mango pulp and the powder obtained from the operational conditions mentioned above. Both integral mango pulp and powder were analyzed as for the following physicochemical characteristics： humidity, pH, titratable acidity, soluble solids （~Brix）, vitamin C and color--through parameters L＊, a＊, b＊ and h0, Chrome （C＊） and color difference （AEL＊a＊b＊）. The experimental planning used presented significant differences at 5% of probability, showing that the model was adjusted to the data in accordance to F test, thus being possible to determine the best process conditions. In addition, the average results of the physicochemical parameters pointed out that the pulp used was in accordance with the patterns established by the quality and identity patterns for mango pulp. Moreover, it showed that the powder obtained had good physicochemical quality.
基金financial support from ADEME for a doctoral fellowship to M.C.is gratefully acknowledged
文摘The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.
文摘This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest reported by the scientific literature regarding the late effects in skeletal muscle resulting from exposure to ionizing radiation. Original and experimental papers mainly containing the key expressions “ionizing radiation” and “effects on skeletal muscle” were searched in computerized databases, and published in any language. Only 33 papers matched the search criteria. Analyzing the investigated radioinduced biological effects in those contributions, four topics were identified as being of major interest: 1) alterations in cellular metabolism and protein degradation;2) repercussions on satellite cells;3) formation of fibrosis and muscle atrophy;4) tissue regeneration. It was verified that no study evaluated possible late effects related to either morphology or properties of skeletal muscles after an exposure to ionizing radiation. Several aspects do not make possible a successful replication;all experiments of eligible group of articles are discussed, such as, lack of raw data, use of no sound methodology and inappropriate statistical technique. Briefly, the subject of this review is an open field of research.
文摘The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national specificities. HyFrance3 is a new project that focuses on the economic competitiveness of different steps of the hydrogen chain, from the production to end usage, at the time horizon of 2030 in France. The project is coordinated by CEA with the other partners being： ADEME （co-funding）, AFH2, CNRS, IFP, Air Liquide, EdF, GdF Suez, TOTAL, ALPHEA. The project is divided into 4 sub-projects, that address present and future French hydrogen industrial markets for chemical ＆ refinery uses, the analysis of the interplay between wind energy production and storage of hydrogen for different automotive requirements （refuelling stations, BtL plants, H2/NG mix）, massive hydrogen storage to balance various offer and demand characteristics, and the supply network （pipeline option competitiveness vs. trucked in supply） to distribute hydrogen in a French region for automotive applications. Technical and economical issues, as well as GHG emissions, are addressed.
基金financially supported by the IFPEN scientific division.
文摘The utilization of photocatalysis for CO_(2) conversion into solar fuels holds significant promise for advancing clean energy solutions;however,there are still many uncertainties regarding the surface mechanisms of the reaction,even for the most commonly studied TiO_(2)-based photocatalytic systems.Of special relevance is the origin of photoconverted products and the role played by adventitious carbon species on the photocatalyst surface,whose nature and origin lack unambiguous identification to date.In this study,we investigated the dynamic nature of vapor-phase photocatalytic CO_(2) reduction using a benchmark Pt/TiO_(2) photocatalyst.To identify carbon species on the photocatalyst surface,we reported a comprehensive analytical approach involving X-ray photoelectron spectroscopy (XPS),thermogravimetric analysis (TGA),and operando Fourier-transform infrared (FTIR) spectroscopy during the activation and photocatalytic reduction of CO_(2).Through this multi-technique approach,we were able to differentiate initial carbonaceous surface species and identify active intermediates during reactions.Upon irradiation,carbon species in the form of carboxylates get involved in reactions with photocatalytically activated surface adsorbed water and can contribute to 40% of methane yields in the first few minutes of irradiation,therefore hindering a reliable quantification of CO_(2) conversion levels.This was confirmed by exposure of the catalyst to light and water vapor during ten irradiation cycles,which significantly reduced the amount of methane and C-species on the catalyst surface.Transient activity was identified as the dominant factor driving methane production.Moreover,reactivation of the catalyst can be achieved through periodic irradiation conditions,leading to a remarkable 60% increase in methane production yields during 180 minutes of irradiation.These findings shed light on the mechanisms occurring on the photocatalyst surface upon light/dark transition steps and demonstrate the potential for enhancing CO_(2) photoreduction performance through periodic irradiation strategies.
基金supported by the French Research Agency(ANR CATCALL(ANR-19-CE07-0025))Numerical calculations in this paper were performed using the Froggy platform of the GRICAD infrastructure(https://www.gricad.univ-grenoblealpes.fr),which is supported by the Rhône-Alpes region(GRANT CPER07-13 CIRA)the Equip@Meso project(reference ANR-10-EQPX-29-01)of the program Investissements d’Avenir supervised by the French Research Agency.
文摘Using a prototypical family of hierarchical zeolites,we show how adsorption-based characterization can be extended to provide morphological and topological assessment beyond state-of-the-art tools.The well-controlled materials under study consist of submicron-sized zeolite crystals(silicalite-1)that exhibit large nanoporous cavities in addition to their intrinsic microporosity.Such zeolites nanoboxes can be prepared with a single large cavity,with several independent cavities or with several interconnected cavities depending on synthesis conditions.It is shown that analysis of the adsorption/desorption branches using the Derjaguin model allows determining the cavity size distributions in these materials but also the fraction of pores directly connected to the external surface for each cavity size.Moreover,using the independent domain theory,we illustrate how scanning the capillary hysteresis provides a means to determine whether pores behave independently from each other or are connected to each other.All our findings are found to be consistent with additional electron microscopy data including electron tomography data.
文摘As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion characteristics,reactivity,and exhaust gas compositions compared to conventional fuels,raising questions about the suitability of lubricants in engines operating with them.The impact of ammonia,hydrogen,and their blends on lubricants in internal combustion engines is a relatively new topic,with few reference studies available.However,degradation processes of lubricants have been studied in the context of hydrocarbon fuels,and in compressors using ammonia as a refrigerant,for example.This work presents a review of the literature on engine oil degradation phenomena in relation to ammonia and hydrogen combustion characteristics.In particular,it highlights the current state of knowledge regarding compatibility with unburnt gases,elevated nitrogen oxide levels,and water.Additionally,it summarizes the latest insights into the contribution of lubricants to pollutant emissions.
