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Enzymatic synthesis of isoamyl acetate with immobilized Candida antarctica lipase in supercritical carbon dioxide
M.P. Romero, L. Calvo, C. Alba, Maja Leitgeb, Mateja Primožič, Željko Knez, 2005, izvirni znanstveni članek

Opis: Isoamyl acetate was successfully synthesized from isoamyl alcohol in supercritical carbon dioxide by enzymatic catalysis. First, the impact of the acyl donor was investigated. Among several reactants, including acetic acid and two different acetates, acetic anhydride gave best yields. Then, two different immobilized lipases (Novozym 435 from Candida antarctica and Lipozyme RM-IM from Rhizomucor miehei) as biocatalysts for the above-mentionedreaction were compared. An esterification extent of 100% was obtained in continuous operation using acetic anhydride as acyl donor and Novozym 435 as enzyme. The amount of enzyme preparation was optimised to 6.25 g/mol alcohol. The effect of substrates load in the solvent was investigated. Operating at a CO2žsubstrates molar ratio below 7.0, the conversion of alcoholdecreased, probably due to an inhibitory effect on enzyme by high concentration of acetic anydride or by produced acetic acid. Pressure in the range of 8-30 MPa showed no effect on this reaction, while an increase in temperature (over 313 K) led to lower production of isoamyl acetate. Novozym 435 was very stable not finding any loss of activity during one month of continuous operation. Finally, carbon dioxide was compared to a conventional organic solvent (n-hexane). Initial reaction rate was higher in SC-CO2, although final esterification extent was similar in both media.
Ključne besede: chemical processing, high pressure technology, superkritical CO2, ester synthesis, isoamyl acetate, enzymatic catalysis, immobilized lipase, isoamyl acetate production, natural flavors
Objavljeno: 01.06.2012; Ogledov: 825; Prenosov: 4
URL Celotno besedilo (0,00 KB)

Reactivation system for proton-exchange membrane fuel-cells
Carlos Restrepo, Oriol Avino, Javier Calvente, Alfonzo Romero, Miro Milanovič, Roberto Giral, 2012, izvirni znanstveni članek

Opis: In recent years, Proton-Exchange Membrane Fuel Cells (PEMFCs) have been the focus of very intensive researches. Manufacturers of these alternative power sources propose a rejuvenation sequence after the FC has been operating at high power for a certain period of time. These rejuvenation methods could be not appropriate for the reactivation of the FC when it has been out of operation for a long period of time or after it has been repaired. Since the developed reactivation system monitors temperature, current, and the cell voltages of the stack, it could be also useful for the diagnostic and repairing processes. The limited number of published contributions suggests that systems developing reactivation techniques are an open research field. In this paper, an automated system for reactivating PEMFCs and results of experimental testing are presented.
Ključne besede: reactivation system, PEM fuel cell, automated system
Objavljeno: 21.06.2017; Ogledov: 29; Prenosov: 3
.pdf Celotno besedilo (789,13 KB)

New perspectives for computer-aided discrimination of Parkinson's disease and essential tremor
Petra Povalej, J.A. Gallego, J. P. Romero, Vojko Glaser, E. Rocon, Julián Benito-León, Félix Bermejo-Pareja, Ignacio Posada, Aleš Holobar, 2017, izvirni znanstveni članek

Opis: Pathological tremor is a common but highly complex movement disorder, affecting ~5% of population older than 65 years. Different methodologies have been proposed for its quantification. Nevertheless, the discrimination between Parkinson's disease tremor and essential tremor remains a daunting clinical challenge, greatly impacting patient treatment and basic research. Here, we propose and compare several movement-based and electromyography-based tremor quantification metrics. For the latter, we identified individual motor unit discharge patterns from high-density surface electromyograms and characterized the neural drive to a single muscle and how it relates to other affected muscles in 27 Parkinson's disease and 27 essential tremor patients. We also computed several metrics from the literature. The most discriminative metrics were the symmetry of the neural drive to muscles, motor unit synchronization, and the mean log power of the tremor harmonics in movement recordings. Noteworthily, the first two most discriminative metrics were proposed in this study. We then used decision tree modelling to find the most discriminative combinations of individual metrics, which increased the accuracy of tremor type discrimination to 94%. In summary, the proposed neural drive-based metrics were the most accurate at discriminating and characterizing the two most common pathological tremor types.
Ključne besede: Parkinson's disease, essential tremor, electromyography, wrist movements, motor units, muscular excitation, decision tree
Objavljeno: 03.11.2017; Ogledov: 48; Prenosov: 2
.pdf Celotno besedilo (3,31 MB)

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