Membranes have been increasingly considered as a promising technology to conventional crystallization processes. One of the most significant benefits would be to control the supersaturation by ...fine-tuning the mass transfer throughout the membrane. Several investigations on this topic have already been proposed using porous materials. However, numerous authors dealt with scaling phenomena with either pore blocking or surface fouling. To reduce this issue, the use of dense skin membranes seems to be an interesting alternative while keeping other membrane advantages. The present study aims at analyzing the potential of nonporous materials in membrane contactors used for crystallization purposes. More specifically, two major scientific challenges are investigated closely: how to avoid membrane fouling by choosing appropriate membrane materials and to predict, potentially, the crystallization location in/on a dense polymeric material. The global aim of this study is to better understand the fouling mechanisms in dense membranes. Several commercially available materials are screened and experiments are conducted under a strict diffusion regime in a gas–liquid system with a stagnant liquid phase at 20 °C. Impact of no-hydrodynamics parameters on the crystallization location is studied, namely, changes in gas flowrate, membrane thickness, polymer type, physical state, and initial moisture. It is shown that the first major key parameter to be considered to prevent fouling is the surface energy of the material. The results obtained highlight that hydrophilic membranes such as cellulose acetate are much more difficult to clean than hydrophobic membranes, such as fluorinated ethylene propylene (FEP). This material property will impact the adherence of a solid compound on the membrane. The permeability of all chemical reactants and their interaction with the membrane materials are the second key parameter to investigate carefully. The results obtained show that no crystals are present on the surface of hydrophobic and highly permeable polymers, such as polydimethylsiloxane (PDMS) or Teflon AF 2400; meanwhile, large amounts of crystals are recovered in the solution. On the contrary, crystals are dropped off the membrane surface of hydrophobic but less permeable polymers like FEP, although the amount of crystals recovered in the solution compartment is at least 10 times lower by using FEP than PDMS or Teflon AF 2400. These two parameters have a crucial incidence on the solid deposit location in/on the membrane. In the context of this study, membrane fouling is expected to be avoided by using appropriate hydrophobic and highly permeable dense membranes such as Teflon AF 2400 and PDMS.
Sustainable biocatalysis syntheses have gained considerable popularity over the years. However, further optimizations – notably to reduce costs – are required if the methods are to be successfully ...deployed in a range of areas. As part of this drive, various enzyme immobilization strategies have been studied, alongside process intensification from batch to continuous production. The flow bioreactor portfolio mainly ranges between packed bed reactors and wall‐immobilized enzyme miniaturized reactors. Because of their simplicity, packed bed reactors are the most frequently encountered at lab‐scale. However, at industrial scale, the growing pressure drop induced by the increase in equipment size hampers their implementation for some applications. Wall‐immobilized miniaturized reactors require less pumping power, but a new problem arises due to their reduced enzyme‐loading capacity. This review starts with a presentation of the current technology portfolio and a reminder of the metrics to be applied with flow bioreactors. Then, a benchmarking of the most recent relevant works is presented. The scale‐up perspectives of the various options are presented in detail, highlighting key features of industrial requirements. One of the main objectives of this review is to clarify the strategies on which future study should center to maximize the performance of wall‐immobilized enzyme reactors.
Continuous biocatalysis production is mainly performed using packed bed and wall‐immobilized enzyme reactors. Maximization of the space‐time‐yield, STY, gives highest turnover numbers, TN, which tends to be increased with the use of wall‐enzyme reactor due to improved specific productivities, Psp. This review also clarifies the strategies to be studied in the future to maximize the wall‐enzyme reactor performances and allow its scalability.
The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a ...column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst support. A simple and efficient crankshaft-inspired system applied in situ compression/relaxation movements to the foam bed. For the first time, the catalytic support parameters (i.e., porosity, tortuosity, characteristic length, etc.) underwent cyclic and controlled changes over time. These dynamic cycles have made it possible to intensify the transfer of gas to liquid at a constant energy level. The application chosen was the selective hydrogenation of phenylacetylene to styrene in an alcoholic solution using a palladium-based catalyst under hydrogen bubble conditions. The conversion observed with this EcFR at 1 Hz as cycle frequency was compared with that observed with a conventional Fixed Catalytic Foam-bed Reactor (FcFR).
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•Innovative elastic foam-bed reactor for continuous gas–liquid reactions.•Mass transfer intensification with a low additional electric power.•Original routes for supported carbonic ...anhydrase.•An intensified process for CO2 capture.
Open-cell polymer foams are memory shape materials with remarkable transport properties. We have designed an elastic foam-bed reactor based on these features to intensify gas–liquid mass transfer of CO2 through in situ foam compression/decompression cycles. The cycles are ensured by a crankshaft and only a low additional electric power (<50 Watts) is required under upflow co-current conditions in order to improve the mass transfer by one order to magnitude compared to fixed foam-bed reactor (i.e. without cycles). CO2 capture is improved thanks to carbonic anhydrase-supported foam (1.3 mg of enzyme per cm3 of foam) using a supramolecular hydrogel for continuous applications.
Recombinant hepatitis B vaccine is usually well tolerated. Clinical and laboratory test manifestations with immunologic mechanisms have nonetheless been described following use of this vaccine. We ...retrospectively report 7 cases of thrombocytopenia occurring within 3 months (7 weeks on the average) of 1 or following injections of recombinant hepatitis B vaccine. Four boys and 3 girls, average age 12 y, were involved. Three had a history of immune thrombocytopenic purpura. Four had haemorrhagic manifestations. The haemogram showed thrombocytopenia (24 x 10(9)/l on the average) without alterations of the other lines. Infectious and immune aetiologies were excluded in all cases. The course varied after treatment by corticosteroids, high-dose intravenous immunoglobulin, or both. After describing the different manifestations subsequent to recombinant hepatitis B vaccination, we discuss post-vaccinal thrombocytopenias (vaccines in question, mechanisms) and the reality of this entity.
Abstract Background Description and comparison of bacterial characteristics of ventilator-associated pneumonia (VAP) between critically ill intensive care unit (ICU) patients with COVID-19-positive, ...COVID + ; and non-COVID-19, COVID-. Methods Retrospective, observational, multicenter study that focused on French patients during the first wave of the pandemic (March–April 2020). Results 935 patients with identification of at least one bacteriologically proven VAP were included (including 802 COVID +). Among Gram-positive bacteria, S. aureus accounted for more than two-thirds of the bacteria involved, followed by Streptococcaceae and enterococci without difference between clinical groups regarding antibiotic resistance. Among Gram-negative bacteria, Klebsiella spp. was the most frequently observed bacterial genus in both groups, with K. oxytoca overrepresented in the COVID- group (14.3% vs . 5.3%; p < 0.05). Cotrimoxazole-resistant bacteria were over-observed in the COVID + group (18.5% vs . 6.1%; p <0.05), and after stratification for K. pneumoniae (39.6% vs . 0%; p <0.05). In contrast, overrepresentation of aminoglycoside-resistant strains was observed in the COVID- group (20% vs . 13.9%; p < 0.01). Pseudomonas sp. was more frequently isolated from COVID + VAPs (23.9% vs . 16.7%; p <0.01) but in COVID- showed more carbapenem resistance (11.1% vs . 0.8%; p <0.05) and greater resistance to at least two aminoglycosides (11.8% vs . 1.4%; p < 0.05) and to quinolones (53.6% vs . 7.0%; p <0.05). These patients were more frequently infected with multidrug-resistant bacteria than COVID + (40.1% vs . 13.8%; p < 0.01). Conclusions The present study demonstrated that the bacterial epidemiology and antibiotic resistance of VAP in COVID + is different from that of COVID- patients. These features call for further study to tailor antibiotic therapies in VAP patients.
3-M syndrome is an autosomal recessive disorder characterized by severe pre- and postnatal growth retardation and minor skeletal changes. We have previously identified CUL7 as a disease-causing gene ...but we have also provided evidence of genetic heterogeneity in the 3-M syndrome. By homozygosity mapping in two inbred families, we found a second disease locus on chromosome 2q35-36.1 in a 5.2-Mb interval that encompasses 60 genes. To select candidate genes, we performed microarray analysis of cultured skin fibroblast RNA from one patient, looking for genes with altered expression; we found decreased expression of IGFBP2 and increased expression of IGFBP5. However, direct sequencing of these two genes failed to detect any anomaly. We then considered other candidate genes by their function/location and found nine distinct mutations in the OBSL1 gene in 13 families including eight nonsense and one missense mutations. To further understand the links between OBSL1, CUL7, and insulin-like growth factor binding proteins (IGFBPs), we performed real-time quantitative PCR (RT-PCR) analysis for OBSL1, CUL7, IGFBP2, and IGFBP5, using cultured fibroblast RNAs from two patients with distinct OBSL1 mutations (p.F697G; p.H814RfsX15). We found normal CUL7 mRNA levels but abnormal IGFBP2 and IGFBP5 mRNA levels in the two patients, suggesting that OBSL1 modulates the expression of IGFBP proteins. Hum Mutat 30:1-7, 2009.
Moulins et meuniers Belmont, Alain; Bolòs, Jordi; Comet, Georges ...
2002
Book
Odprti dostop
Le moulin n’est pas seulement le bâtiment industriel par excellence de l’ancienne Europe. Il est aussi un “fait social total” dont l’étude implique la pluridisciplinarité. Archéologues, historiens, ...ethnologues, spécialistes de la littérature et de la parémiologie sont rassemblés dans ce livre pour faire le point des connaissances et, ce faisant, restituer une galerie d’images contrastées allant de la silhouette du seigneur rapace au sourire de la “belle meunière”.
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