Papers by Carlos Guillermo Vera Vera
Mechanical Systems and Signal Processing, Mar 1, 1991
A large number of methods have been developed in order to solve the eigenvalues and eigenvectors ... more A large number of methods have been developed in order to solve the eigenvalues and eigenvectors of mechanical systems, from a generic treatment through to finite elements. For accuracy to be guaranteed in the results, a through discrete-parameters procedure should be performed on the model which, when many degrees of freedom are involved, implies resolution of a high-order system at the expense of considerable computer time. An alternative method is proposed in this paper for calculating natural frequencies and modes based on building the dynamic matrix through Bond Graph techniques.
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Actas Del I Congreso Nacional De Innovacion Ferroviaria I Congreso Nacional De Innovacion Ferroviaria 05 10 2004 06 10 2004 Calatayud Espana, Oct 5, 2004
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Proceedings of the Eight International Conference on Maintenance Renewal of Permanent Way Power Signaling Structures Earthworks Eight International Conference on Maintenance Renewal of Permanent Way Power Signaling Structures Earthworks 29 30 June 2005 London, Jun 1, 2005
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Annals of Biomedical Engineering, Dec 1, 2003
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Vehicle System Dynamics International Journal of Vehicle Mechanics and Mobility Issn 0042 3114 2006 08 Vol 44 N 8, Aug 1, 2006
Overhead rigid conductor arrangements for current collection for railway traction have some advan... more Overhead rigid conductor arrangements for current collection for railway traction have some advantages compared to other, more conventional, energy supply systems. They are simple, robust and easily maintained, not to mention their flexibility as to the required height for installation, which makes them particularly suitable for use in subway infrastructures. Nevertheless, due to the increasing speeds of new vehicles running
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Annals of Biomedical Engineering the Journal of the Biomedical Engineering Society, May 20, 2010
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Biophysical Journal, Jul 15, 2007
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Journal of Biotechnology, 2015
Lactulose and galacto-oligosaccharides (GOS) are well recognized prebiotics derived from lactose.... more Lactulose and galacto-oligosaccharides (GOS) are well recognized prebiotics derived from lactose. In the synthesis of lactulose with β-galactosidases GOS are also produced, but the ratio of lactulose and GOS in the product can be tuned at will, depending on the operation conditions, so to obtain an optimal product distribution in terms of prebiotic potential. The selectivity of fermentation of each carbohydrate alone as well as mixtures of both was determined using pH-controlled anaerobic batch cultures with faecal inoculum. Within the experimental range considered, lactulose/GOS molar ratio of 4 resulted in the highest selectivity for Bifidobacterium and Lactobacillus/Enterococcus, so this ratio was selected as the target for the synthesis of lactulose from fructose and lactose with Aspergillus oryzae β-galactosidase. Synthesis was optimized using response surface methodology, considering temperature, initial concentrations of acceptor sugars and fructose/lactose molar ratio as key variables, with the aim of maximizing lactulose yield at the optimal product distribution in terms of prebiotic potential (lactulose/GOS molar ratio of 4). Under optimal conditions (50°C, 50% w/w total initial concentrations of sugars and fructose/lactose molar ratio of 6.44), lactulose yield of 0.26g of lactulose produced per g of initial lactose was obtained at the optimal product distribution.
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Bioresource Technology, 2015
Synthesis of lactulose under repeated-batch operation was done with cross-linked aggregates of As... more Synthesis of lactulose under repeated-batch operation was done with cross-linked aggregates of Aspergillus oryzae β-galactosidase (CLAGs). The effect of the crosslinking agent to enzyme mass ratio and cross-linking time were first evaluated. Best results were obtained at 5.5gdeglutaraldehyde/g enzyme at 5h of cross-linking, obtaining a specific activity of 15,000IUg(-1), with 30% immobilization yield. CLAG was more stable than the free enzyme under non-reactive conditions with a half-life of 123h at 50°C and when operated in repeated-batch mode, yield and productivity was 3.8 and 4.3 times higher. Maximum number of batches was determined considering biocatalyst replacement at 50% residual activity. 98 and 27 batches could be performed under such criterion at fructose/lactose molar ratio of 4 and 20 respectively, reflecting that enzyme stability is strongly affected by the sugars distribution in the reaction medium.
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American journal of physiology. Heart and circulatory physiology, 2003
Tropomodulins are a family of proteins that cap the slow-growing end of actin filaments. Erythroc... more Tropomodulins are a family of proteins that cap the slow-growing end of actin filaments. Erythrocyte tropomodulin (E-Tmod) stabilizes short actin protofilaments in erythrocytes and caps longer sarcomeric actin filaments in striated muscles. We report the knockin of the beta-galactosidase gene (LacZ) under the control of the endogenous E-Tmod promoter and the knockout of E-Tmod in mouse embryonic stem cells. E-Tmod(-/-) embryos die around embryonic day 10 and exhibit a noncontractile heart tube with disorganized myofibrils and underdevelopment of the right ventricle, accumulation of mechanically weakened primitive erythroid cells in the yolk sac, and failure of primary capillary plexuses to remodel into vitelline vessels, all required to establish blood circulation between the yolk sac and the embryo proper. We propose a hemodynamic "plexus channel selection" mechanism as the basis for vitelline vascular remodeling. The defects in cardiac contractility, vitelline circulatio...
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Enzyme and Microbial Technology, 2015
β-Galactosidases exhibit both hydrolytic and transgalactosylation activities; the former has been... more β-Galactosidases exhibit both hydrolytic and transgalactosylation activities; the former has been used traditionally for the production of delactosed milk and dairies, while the latter is being increasingly used for the synthesis of lactose-derived oligosaccharides: balance between both activities was highly dependent on the enzyme origin: β-galactosidases from Aspegillus oryzae and Bacillus circulans exhibited high transgalactosylation activity, while those from one from Kluyveromyces exhibited high hydrolytic activity but quite low transgalactosylation activity. Also the affinity for the donors (lactose or lactulose) and the acceptors (lactose, lactulose or fructose) of transgalactosylated galactose was dependent on the enzyme origin, as reflected by the Michaelis constants obtained in the synthesis of galacto-oligosaccharides, fructosyl-galacto-oligosaccharides and lactulose. Finally, the balance between transgalactosylation and hydrolytic activities of β-galactosidases could be tuned by changing the concentration of galactose donor.
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International Dairy Journal, 2014
ABSTRACT Galacto-oligosaccharides (GOS) were synthesised from 50% (w/w) lactose with Aspergillus ... more ABSTRACT Galacto-oligosaccharides (GOS) were synthesised from 50% (w/w) lactose with Aspergillus oryzae β-galactosidase. Reacted medium without nutrient supplementation (raw GOS) was fermented with Kluyveromyces marxianus cells obtaining GOS of 95% purity containing mostly tri- and tetrasaccharides with total recovery of GOS after 24 h. The effect of the initial concentration of carbohydrate was assessed in the range of 10 to 50% (w/w), such purity being obtained even at 50% (w/w) (undiluted raw GOS) though being strongly influenced by the dry cell to total carbohydrate mass ratio (RCC). The process of purification by selective fermentation of raw GOS at 20% (w/w) was optimised in terms of the specific productivity of unwanted carbohydrate removal, considering temperature, pH and RCC as operational variables. According to the experimental design, maximum specific productivity predicted was 0.16 g g-1 h-1, obtained at the optimal operating conditions of 40 °C, pH 3.5 and RCC 1.55 g g-1.
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Process Biochemistry, 2011
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Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 2005
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Physiological Measurement, 2009
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Physical Review B, 2009
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New Biotechnology, 2012
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New Biotechnology, 2009
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Journal of Molecular Catalysis B: Enzymatic, 2011
Commercial β-galactosidase preparations from Bacillus circulans, Kluyveromyces lactis and Aspergi... more Commercial β-galactosidase preparations from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae were evaluated as catalysts for the synthesis of lactulose. Among them, the enzyme from A. oryzae was selected for further studies. The effect of reaction conditions was then studied on product composition during the kinetically controlled synthesis of lactulose by transgalactosylation with A. oryzae β-galactosidase. Product composition was not
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Papers by Carlos Guillermo Vera Vera