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Column Used (column + used)
Selected AbstractsEnhanced production of lovastatin in a bubble column by Aspergillus terreus using a two-stage feeding strategyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2007EM Rodríguez Porcel Abstract A two-stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed-batch phase and a semi-continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi-continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two-stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry [source] Modified evolving window factor analysis for process monitoringJOURNAL OF CHEMOMETRICS, Issue 9 2004S. Kamaledin Setarehdan Abstract Reaction process monitoring and control are usually involved with direct measurement or indirect model-based prediction of concentration profiles of the constituents of interest in a chemical reaction at regular time intervals. These approaches are expensive, time-consuming and sometimes impossible. On the other hand, application of so-called ,calibration-free' techniques such as EFA and EWFA to spectral data usually provides important information regarding the structural variations in the chemical system without identification of the chemical components responsible for the variations. In this paper a novel spectral data pre-processing algorithm is presented which helps EWFA to extract the concentration trends of the components of interest within the reaction. The proposed algorithm uses the pure spectrum of the component of interest to develop a so-called ,weighting filter' which is applied to the input spectral information before EWFA. The algorithm was applied to a real Raman spectral data set obtained from a pre-treatment distillation column used for removing unwanted heavy/cyclic hydrocarbons from naphtha in an oil company. Comparison of the concentration trends resulting from the proposed algorithm with those obtained using conventional PLS1 models shows that the new calibration-free and on-line algorithm outperforms the calibration models obtained by difficult and expensive laboratory work. Copyright © 2005 John Wiley & Sons, Ltd. [source] Experimental and thermal analysis of washing the packed ice bed in wash columnsAICHE JOURNAL, Issue 11 2009Frank G. F. Qin Abstract In the process of freeze concentration (FC), the main problems in operating the counter-current wash column used for separating ice from ice slurries are channeling and viscous fingering. These phenomena lead to the mixing of pure water and mother liquid, as well as entrainment of mother liquid within the removed ice. Experimental and thermal analysis of the wash front interface in this research relates ice melting and wash front breakthrough with the operating conditions (such as the wash water temperature, ice bed temperature and porosity). Criteria for wash front stability are proposed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The making and muting of an indigenous media activist: Imagination and ideology in Charles Round Low Cloud's "Indian News"AMERICAN ETHNOLOGIST, Issue 3 2010GRANT ARNDT ABSTRACT In this article, I examine an example of American Indian activism through the once-dominant mass medium of the newspaper. I focus on Ho-Chunk author Charles Round Low Cloud and his development of an "Indian News" column into a vehicle for activism against everyday forms of racial oppression in the 1930s and on the ways others involved in publishing his column used the medium to subvert his message. The analysis shows how nonindigenous actors can mute activist messages through practices designed to celebrate indigenous voices. I argue that both indigenous media activism and reactions against such activism rely on the "mediated imagination": the mediation of the use and reception of media messages by cultural ideologies and by individual creativity. Recognition of the mediated imagination, therefore, complements efforts to understand how language and other semiotic ideologies shape interpretations of social reality. It also facilitates analysis of the potentials and limitations of indigenous activism that uses existing media technologies. [source] Assessment of the repeatability and reproducibility of hydrogen/deuterium exchange mass spectrometry measurements,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008William Burkitt A system to perform automated hydrogen/deuterium exchange mass spectrometry measurements was constructed using an XYZ robotic autosampler that was capable of performing solvent manipulations and a 4.7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The system included features such as the first demonstration of a ,dual column' high-performance liquid chromatography (HPLC) setup, and a novel digestion strategy. The performance of the system, in terms of the repeatability and reproducibility of the measurement of protein hydrogen/deuterium exchange, was assessed over a 2-month period. The sensitivity of the measurement of hydrogen exchange towards several parameters was assessed, which allowed their impact on the reproducibility to be discussed. The parameters assessed were the temperature of the HPLC columns and switching valves, the temperature of the quench solutions, the pH of the mobile phase, the pH of the quenched solution, the acid used in the mobile phase and the analytical column used. Copyright © 2008 John Wiley & Sons, Ltd. [source] Utility of porous graphitic carbon stationary phase in quantitative liquid chromatography/tandem mass spectrometry bioanalysis: quantitation of diastereomers in plasmaRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2006Yuan-Qing Xia A major challenge in selecting an appropriate stationary phase for diastereomeric separation is that it is difficult to predict which of the commercially available stationary phases could achieve the required liquid chromatographic (LC) separation. This work describes the selection and evaluation of a porous graphitic carbon (PGC) column coupled with tandem mass spectrometry (MS/MS) for the simultaneous quantitation of an experimental drug candidate (I), its two diastereomeric metabolites (II and III), and its demethylated metabolite (IV) in rat plasma. In addition, we investigated the PGC column for the separation of another drug candidate (VI), its two diastereomeric metabolites (VII and VIII) and its ketone metabolite (IX). The PGC column showed excellent chromatographic resolution for the two diastereomers II and III, as well as for VII and VIII. In contrast, the required resolution for the diastereomers II and III could not be achieved using silica-bonded C18, C30, phenyl, perfluorinated, polar embedded and polar end-capped phases. The PGC column showed ruggedness with excellent reproducibility of retention times, peak symmetry and response over a period of more than 400 injections of a plasma acetonitrile-precipitation extract. Excellent accuracy and precision were achieved, with accuracy of 94,108% and intra- and inter-run precision within 9%. This work indicates that PGC is a valuable addition to the repertoire of LC columns used for quantitative LC/MS/MS bioanalysis, especially where the separation and quantitation of diastereomeric analytes is involved. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||