4,122 research outputs found

    The influence of pain obesity and quadriceps strength on the gait of osteoarthritis patients

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    Chiral separation by SMB chromatography

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    The paper deals with chiral separation by simulated moving bed (SMB) chromatography. A model for the prediction of the cyclic steady-state performance of the SMB, based on the analogy with the true moving bed (TMB), is developed assuming multicomponent adsorption equilibria, axial dispersion flow and the linear driving force approximation to describe the intraparticle mass transfer rate. The simulation package is used to predict the effect of operating variables on the process performance and to define the regions for enantiomers separation. The influence of mass transfer resistance in the separation region is analyzed. A practical tool for choosing the better SMB operating conditions as a function of the feed flow-rate is proposed. The experimental operation of a pilot unit of SMB, Licosep 12-26 (Novasep, France), is carried out for the separation of enantiomers and illustrated with two systems: the bi-naphthol and the chiral epoxide enantiomers. Experimental results and model predictions are compared in terms of process performance and internal concentration profiles

    Separation of 1,1'-bi-2-naphthol enantiomers by continuous chromatography in simulated moving bed

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    The chromatographic separation of 1,1′-bi-2-naphthol enantiomers with 3,5-dinitrobenzoyl phenylglycine bonded to silica gel stationary phases is studied. Continuous chromatography in simulated moving bed (SMB) is analyzed by modeling, simulation and operation of a SMB pilot unit Licosep 12–26 from Separex (France). A model for the prediction of the cyclic steady-state performance of the SMB is developed based on the analogy with the true moving bed (TMB). The model assumes axial dispersion flow for the liquid phase, linear driving force (LDF) approximation for intraparticle mass transfer rate and takes into account multicomponent adsorption equilibria. The SMB package allows the simulation of the pilot unit. The effect of operating variables (switching time, extract and feed flow rates, section length) and number of mass transfer units on the SMB performance is analyzed. The SMB performance is characterized by purity, recovery, solvent consumption and adsorbent productivity. The package also allows the simulation of the dynamic evolution of internal profiles for the transient operation of a TMB. The operation of the SMB pilot unit was carried out for the separation of racemic mixtures of bi-naphthol enantiomers. Using a 8-column configuration purities as high as 94.5% of the more retained species in the extract and 98.9% of the less retained species in the raffinate were obtained

    Modeling strategies for enantiomers separation by SMB chromatography

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    Modeling strategies for simulated moving bed adsorbers were studied to compare the simulated moving bed model (SMB) that considers the real shift of the injection and collection points to the true moving bed approach (TMB) that considers liquid and solid flow in opposite directions. The prediction of these two models is compared in terms of steady-state performance, steady-state internal concentration profiles, and transient behavior of the extract and raffinate purities. The influence of the degree of subdivision of the bed in the SMB model predictions is also analyzed and compared with the TMB performance. Model results are compared with experimental results obtained for the chromatographic separation of binaphthol enantiomers

    Separation of enantiomers of a chiral epoxide by simulated moving bed chromatography

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    The paper deals with chiral separation by simulated moving bed (SMB) chromatography. The separation of chiral epoxide enantiomers in microcrystalline cellulose triacetate using methanol as eluent is considered as illustrative example. The use of microcrystalline cellulose triacetate for the chromatographic separation of enantiomers is first reviewed and a methodology for obtaining basic data (adsorption equilibrium isotherms, axial dispersion and mass transfer coefficient) is discussed. A model for the prediction of the cyclic steady-state performance of the SMB, based on the analogy with the true moving bed, is developed assuming multicomponent adsorption equilibria, axial dispersion flow and linear driving force approximation to describe the intraparticle mass transfer rate. The simulation package is used to predict the effect of operating variables on the process performance and to define the regions for enantiomer separation. A simple optimization procedure is proposed for choosing the best SMB operating conditions. This procedure is extensively tested for the separation of chiral epoxide enantiomers. The experimental operation of a SMB pilot unit was carried out for this system. Purities and recoveries higher than 90% were obtained for both extract and raffinate, using a 420 ml inventory of stationary phase. The SMB pilot allows the continuous resolution of 52 g of racemic mixture per day and per liter of bed, with a solvent consumption of 0.4 l of mobile phase per gram of racemic mixture processed. The simulation package is also used to predict the steady-state internal concentration profiles for the SMB operation with reasonable agreement with experimental results

    Organogenic Nodule Formation in Hop: A Tool to Study Morphogenesis in Plants with Biotechnological and Medicinal Applications

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    The usage of Humulus lupulus for brewing increased the demand for high-quality plant material. Simultaneously, hop has been used in traditional medicine and recently recognized with anticancer and anti-infective properties. Tissue culture techniques have been reported for a wide range of species, and open the prospect for propagation of disease-free, genetically uniform and massive amounts of plants in vitro. Moreover, the development of large-scale culture methods using bioreactors enables the industrial production of secondary metabolites. Reliable and efficient tissue culture protocol for shoot regeneration through organogenic nodule formation was established for hop. The present review describes the histological, and biochemical changes occurring during this morphogenic process, together with an analysis of transcriptional and metabolic profiles. We also discuss the existence of common molecular factors among three different morphogenic processes: organogenic nodules and somatic embryogenesis, which strictly speaking depend exclusively on intrinsic developmental reprogramming, and legume nitrogen-fixing root nodules, which arises in response to symbiosis. The review of the key factors that participate in hop nodule organogenesis and the comparison with other morphogenic processes may have merit as a study presenting recent advances in complex molecular networks occurring during morphogenesis and together, these provide a rich framework for biotechnology applications

    Employability and Higher Education: The Case Study of ESTM Master's Degree

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    The labor market in this globalized world, based on new technologies, is constantly changing. In an increasingly demanding and dynamic world of human resources competences, young people have to focus on their training in order to enter in the labor market better prepared and thus contribute to the success of the entity that receives them and for their own professional and personal fulfillment. The choice of their academic journey is crucial to ensure the achievement of these competences and make that decision is not easy, with a system of higher education such as the Portuguese, where there are so many graduation courses and two systems of teaching, University and Polytechnic. In fact, with the changes introduced in higher education by the so-called Bologna Process, most undergraduate’s courses saw the number of years reduced from five to three years, while others opted for integrated master's degrees. In the case of the School of Tourism and Maritime Technology, the option was to offer three-year degree courses and two-year master's degrees. This study intends to understand where are the students who have bet on their training at the master's level and finish their master's degree at the School of Tourism and Maritime Technology (ESTM) of the Polytechnic of Leiria, if they are working in the area and if the employers recognize these qualifications.info:eu-repo/semantics/publishedVersio
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