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排序方式: 共有142条查询结果,搜索用时 22 毫秒
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2.
Rene M. Ripken Jeffery A. Wood Johannes G. E. Gardeniers Sverine Le Gac 《化学工程与技术》2019,42(10):2179-2186
In heterogeneous catalysis, the creation of gaseous products as bubbles in a liquid phase on the catalytic surface is associated with slip phenomena. In a microreactor, the slip length at the gas‐liquid interface is in the same order of magnitude as the reactor dimensions, which can affect fluid dynamics and transport phenomena. Here, the interplay of momentum, heat and mass transfer in a microreactor, when bubbles form on the catalytic surface, was investigated using two‐dimensional simulations. The effect of bubbles on the endothermic process of aqueous‐phase reforming of a glycerol solution was evaluated in terms of conversion and conversion and temperature in the reactor. Altogether, this study highlights the impact of bubbles, not only on the transport phenomena but also on the reactor performance. 相似文献
3.
Initial Molecular Recognition Steps of McjA Precursor during Microcin J25 Lasso Peptide Maturation
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Dr. Nadine Assrir Dr. Anna Pavelkova Régine Dazzoni Dr. Rémi Ducasse Dr. Nelly Morellet Dr. Eric Guittet Prof. Sylvie Rebuffat Dr. Séverine Zirah Dr. Yanyan Li Dr. Ewen Lescop 《Chembiochem : a European journal of chemical biology》2016,17(19):1851-1858
Microcin J25 (MccJ25) has emerged as an excellent model to understand the maturation of ribosomal precursor peptides into the entangled lasso fold. MccJ25 biosynthesis relies on the post‐translational modification of the precursor McjA by the ATP‐dependent protease McjB and the lactam synthetase McjC. Here, using NMR spectroscopy, we showed that McjA is an intrinsically disordered protein without detectable conformational preference, which emphasizes the active role of the maturation machinery on the three‐dimensional folding of MccJ25. We further showed that the N‐terminal region of the leader peptide is involved in interaction with both maturation enzymes and identified a predominant interaction of V43–S55 in the core McjA sequence with McjC. Moreover, we demonstrated that residues K23–Q34 in the N‐terminal McjA leader peptide tend to adopt a helical conformation in the presence of membrane mimics, implying a role in directing McjA to the membrane in the vicinity of the lasso synthetase/export machinery. These data provide valuable insights into the initial molecular recognition steps in the MccJ25 maturation process. 相似文献
4.
Séverine Goscinny Hermann Unterluggauer Jasmin Aldrian Vincent Hanot Sonja Masselter 《Food Analytical Methods》2012,5(5):1177-1185
A straightforward analytical method has been developed for the determination of glyphosate and aminomethylphosphonic acid (AMPA), its major metabolite in cereals. This method entails a rapid extraction and derivatization with 9-fluorenylmethyl chloroformate followed by separation with a conventional reversed-phase rapid chromatography used in daily routine analysis and detection by electrospray ionization tandem mass spectrometry. To overcome matrix effects and compensate for any analyte losses during sample treatment, an isotopic dilution approach was used. Since 2010, the monitoring of cereals for the widely used herbicide glyphosate is obligatory to all European Union (EU)-member states, laid down in Commission Regulation (EC) No. 1213/2008. Hence, there is definitively a need for a reliable and easy-to-handle analytical method for monitoring of this compound. The proposed method can be run without having to make time-consuming changes on the equipment used for daily routine analysis. The analytical performance of the method was evaluated according to SANCO/10684/2009 criteria and demonstrated that this method is rugged and cost-effective, therefore suitable for monitoring purposes as well as legislative enforcements within the EU. The apparent recoveries of both analytes were between 97% and 113% with relative standard deviations less than 20%. The limits of quantification of glyphosate and AMPA were 0.02 mg/kg in cereal matrices. Finally, the accuracy of the method was assessed by analyzing a proficiency test material which was available from a previous round (EUPT-C4). 相似文献
5.
Xavier Vanhoye Alexandre Janin Amandine Caillaud Antoine Rimbert Fabienne Venet Morgane Gossez Wieneke Dijk Oriane Marmontel Sverine Nony Charlotte Chatelain Christine Durand Pierre Lindenbaum Jennifer Rieusset Bertrand Cariou Philippe Moulin Mathilde Di Filippo 《International journal of molecular sciences》2022,23(8)
Hypobetalipoproteinemia is characterized by LDL-cholesterol and apolipoprotein B (apoB) plasma levels below the fifth percentile for age and sex. Familial hypobetalipoproteinemia (FHBL) is mostly caused by premature termination codons in the APOB gene, a condition associated with fatty liver and steatohepatitis. Nevertheless, many families with a FHBL phenotype carry APOB missense variants of uncertain significance (VUS). We here aimed to develop a proof-of-principle experiment to assess the pathogenicity of VUS using the genome editing of human liver cells. We identified a novel heterozygous APOB-VUS (p.Leu351Arg), in a FHBL family. We generated APOB knock-out (KO) and APOB-p.Leu351Arg knock-in Huh7 cells using CRISPR-Cas9 technology and studied the APOB expression, synthesis and secretion by digital droplet PCR and ELISA quantification. The APOB expression was decreased by 70% in the heterozygous APOB-KO cells and almost abolished in the homozygous-KO cells, with a consistent decrease in apoB production and secretion. The APOB-p.Leu351Arg homozygous cells presented with a 40% decreased APOB expression and undetectable apoB levels in cellular extracts and supernatant. Thus, the p.Leu351Arg affected the apoB secretion, which led us to classify this new variant as likely pathogenic and to set up a hepatic follow-up in this family. Therefore, the functional assessment of APOB-missense variants, using gene-editing technologies, will lead to improvements in the molecular diagnosis of FHBL and the personalized follow-up of these patients. 相似文献
6.
The effluents of wastewater treatment plants (WTTP) discharged into the rivers considerably affect the biogeochemical functioning of the system. In this paper, we characterize both raw and treated domestic wastewater from two WTTPs of Parisian agglomeration using different process treatments (Achères WWTP with a secondary treatment and Colombes WWTP with a tertiary one). In addition to the classical variables, we analyse the input of bacteria, both the heterotrophs and the nitrifyers. Tertiary treatment leads to significantly decrease ammonium-specific load (< 2 g KjN inhab equ.(-1) instead of 9 g KjN inhab equ.(-1) for secondary treatment) and notably reduces the one of organic matter (approximately 2.5 g biological oxygen demand (BOD) inhab equ.(-1) instead of approximately 7.5 g BOD inhab equ.(-1) for secondary treatment); it is therefore promising to improve oxygen status of both the Seine river and its estuary. In terms of total bacterial biomass abatement (the heterotrophs mostly), bioreactors (at Colombes WWTP) eliminate 12% more bacterial biomass than the activated sludge treatment (at Achères WWTP). Regarding the nitrifying bacteria, a tertiary treatment in bioreactors eliminates reverse similar 90% of both nitrifying bacteria and nitrogen pollution of wastewater. Bacterial populations are characterized by large size bacteria (> 1 microm) with a higher growth rate, that represent in the treatment plant effluents 70% of the biomass. These large size bacteria have therefore a strong impact in the organic matter degradation and oxygen consumption. Relationships between classical physical-chemical variables routinely analysed in WWTPs laboratory and bacterial biomass (heterotrophic and nitrifying) are established, in order to quantify the ecological role of the allochthonous bacteria brought into the river system. In addition, domestic specific loads are calculated for both raw and treated effluents of the two types of WWTPs. As the application of the European Water Directive requires to upgrade the wastewater treatment at Achères WWTP as soon as 2007 for 90% nitrification and 30% denitrification and in 2015 for further denitrification (up to 70%), the results of this study can be taken as point-source constraints into the modelling approach already developed for the Seine basin, and chosen to test the implementation of the Water Frame Directive. 相似文献
7.
Séverine A.E. Boyer Michel Gerland Sylvie Castagnet 《Polymer Engineering and Science》2014,54(9):2139-2146
The influence of gas sorption on damage nucleation of a semicrystalline polymer during coupled diffuso‐mechanical monotonic loading in tension was investigated for the first time. Alpha‐poly(vinylidene fluoride) was mechanically strained under the presence of two chemically different gases, hydrogen and carbon dioxide, at a temperature of 30°C and a pressure up to 120 bar. The cavitation damage at the microstructure scale after gas decompression was assessed from a careful SEM and TEM micrographs analysis. Compared with SEM, TEM allowed quantifying the smallest cavities (ten‐nanometer size). If decompression in hydrogen appeared to have only a slight effect on cavitation however, carbon dioxide showed a detrimental effect on damage nucleation with the exhibition of a significant population of small cavities. On the other hand, tension under gas pressure is more sensitive to hydrogen than to carbon dioxide. Once interaction with gaseous carbon dioxide takes place the plasticizing effect is in competition with damage by cavitation. POLYM. ENG. SCI., 54:2139–2146, 2014. © 2013 Society of Plastics Engineers 相似文献
8.
Juan Milanesio Pablo Hegel Yaocihuatl Medina‐González Séverine Camy Jean‐Stéphane Condoret 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(3):378-387
BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high‐lipid‐content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO2) extraction using ethanol as a co‐solvent. Also, high pressure solubility measurements in the systems ‘CO2 + yeast oil’ and ‘CO2 + ethanol + yeast oil’ were carried out. RESULTS: The solubility experiments determined that, at the conditions of the supercritical extractor (40 °C and 20 MPa), a maximum concentration of 10 mg of yeast oil per g of solvent can be expected in pure CO2. 10% w/w of ethanol in the solvent mixture increased this value to almost 15 mg of yeast oil per g of solvent. Different pretreatments were necessary to obtain satisfactory yields in the extraction experiments. The Soxhlet and the ASE method were not able to complete the lipid extraction. The ‘SCCO2 + ethanol’ extraction curves revealed the influence of the different pretreatments on the extraction mechanism. CONCLUSION: Evaluating the effectiveness of a given pretreatment, ASE reduced the amount of material and solvent used compared with Soxhlet. In all three cases, the best total extraction performance was obtained for the ethanol‐macerated yeast (EtM). Addition of ethanol to the solvent mixture enhanced the oil solubility. Oil can be extracted from Y. lipolytica in two different steps: a non‐selective ethanol extraction followed by TAG‐selective SCCO2 purification. © 2012 Society of Chemical Industry 相似文献
9.
In this study, we described and modelled some coupled material transformations with heat and mass transfer phenomena which occur during the convective or the infrared drying of coated films of model car paintings. For these very complex reactive systems -highly shrinking, hygroscopic, semi-transparent (infrared)- the vaporization process is coupled with the polymerization reaction itself which determines significantly the material properties of the dry paint coating. Three model systems (paint + support) were successively defined and investigated by association of five supports of different radiative or adhesive properties -polish aluminium, blackened aluminium, glass, galvanized iron and composite plastic (SMC)- with three model paintings : epoxy-amine system, polyurethane system and polyvinylalcohol (PVA). Two laboratory combined dryers (convective or infrared) were set up in order to control and regulate precisely the main process parameters: aerothermic conditions (temperature and velocity), spectrum (NIR or MIR) and flux density of infrared radiation.
Firstly, the kinetics of the polymerization were followed all along the process by three different techniques : DSC (Differential Scanning Calorimetry), SEC (Size Exclusion Chromatography), FT-ERS (FOURIER Transform Infrared Spectroscopy). The glass transition temperature of the material during the drying process was deduced from DSC data with the fractional conversion of the monomer. These two parameters were well correlated by the DI BENEDETTO'S relationship, thus defining some characteristic curve of the painting system. Drying curves -temperature profiles and drying rates- were determined for PVA systems for many operating conditions, principally infrared flux density, spectra type or air velocity. The two main coating properties necessary for the modeling were deduced from drying experiments 1: the mean radiative absorptivity as a function of the mean moisture content, 2: the water apparent mass diffusivity as a function of the temperature and of the local moisture content. A diffusive model - written with a mobile frame of coordinates (lagrangian coordinates)- associated with an overall heat balance of the support + coating system, has proved capable of predecting very well the drying curves and the temperatures profiles So, this whole set of results -associated with other material properties (rheological, adhesive, color, etc ⃛)- will be useful to rationally optimize the industrial dryers operating in the car manufactories. 相似文献
Firstly, the kinetics of the polymerization were followed all along the process by three different techniques : DSC (Differential Scanning Calorimetry), SEC (Size Exclusion Chromatography), FT-ERS (FOURIER Transform Infrared Spectroscopy). The glass transition temperature of the material during the drying process was deduced from DSC data with the fractional conversion of the monomer. These two parameters were well correlated by the DI BENEDETTO'S relationship, thus defining some characteristic curve of the painting system. Drying curves -temperature profiles and drying rates- were determined for PVA systems for many operating conditions, principally infrared flux density, spectra type or air velocity. The two main coating properties necessary for the modeling were deduced from drying experiments 1: the mean radiative absorptivity as a function of the mean moisture content, 2: the water apparent mass diffusivity as a function of the temperature and of the local moisture content. A diffusive model - written with a mobile frame of coordinates (lagrangian coordinates)- associated with an overall heat balance of the support + coating system, has proved capable of predecting very well the drying curves and the temperatures profiles So, this whole set of results -associated with other material properties (rheological, adhesive, color, etc ⃛)- will be useful to rationally optimize the industrial dryers operating in the car manufactories. 相似文献
10.
Alain Lenoir Stéphanie Depickère Séverine Devers Jean-Philippe Christidès Claire Detrain 《Journal of chemical ecology》2009,35(8):913-921
The cuticular hydrocarbons (CHCs) of the ant Lasius niger are described. We observe a high local colony specificity of the body cuticular profile as predicted for a monogynous and
multicolonial species. The CHCs show a low geographical variation among different locations in France. The CHCs on the legs
also are colony specific, but their relative quantities are slightly different from those on the main body. For the first
time, we demonstrate that the inner walls of the ant nest are coated with the same hydrocarbons as those found on the cuticle
but in different proportions. The high amount of inner-nest marking and its lack of colony-specificity may explain why alien
ants are not rejected once they succeed in entering the nest. The cuticular hydrocarbons also are deposited in front of the
nest entrance and on the foraging arena, with a progressive increase in n-alkanes relative amounts. Chemical marks laid over
the substrate are colony specific only when we consider methyl-branched alkanes. Our data confirm that these “footprint hydrocarbons”
are probably deposited passively by the contact of ant tarsae with the substrate. These results suggest that the CHCs chemical
profiles used by ants in colony recognition are much more complex than a single template: ants have to learn and memorize
odors that vary depending on their context of perception. 相似文献