Multistep variable methods for exact integration of perturbed stiff linear systems

A family of real and analytical functions with values within the ring of M(m, R) is introduced. The solution for linear systems of differential equations is expressed as a series of Φ-functions. This new multistep method is defined for variable-step and variable-order, maintains the good properties of the Φ-function series method. It incorporates to compute the coefficients of the algorithm a recurrent algebraic procedure, based in the existing relation between the divided differences and the elemental and complete symmetrical functions. In addition, under certain hypotheses, the new multistep method calculates the exact solution of the perturbed problem. The new method is implemented in a computational algorithm which enables us to resolve in a general manner some physics and engineering IVP’s modeled by means systems of differential equations. The good behaviour and precision of the method is evidenced by contrasting the results with other-reputed algorithms and even with methods based on Scheifele’s G-functions.This work has been supported by GRE09-13 project of the University of Alicante and the project of the Generalitat Valenciana GV/2011/032

Experimental investigation of a circulating fluidized bed reactor to capture CO2 with CaO

[EN] Calcium looping processes for capturing CO2 from large emissions sources are based on the use of CaO particles as sorbent in circulating fluidized bed (CFB) reactors. A continuous flow of CaO from an oxyfired calciner is fed into the carbonator and a certain inventory of active CaO is expected to capture the CO2 in the flue gas. The circulation rate and the inventory of CaO determine the CO2 capture efficiency. Other parameters such as the average carrying capacity of the CaO circulating particles, the temperature and the gas velocity must be taken into account. To investigate the effect of these variables on CO2 capture efficiency we employed a 6.5 m height CFB carbonator connected to a twin CFB calciner. Many stationary operating states were achieved using different operating conditions. The trends of CO2 capture efficiency measured are compared with those from a simple reactor model. This information may contribute to the future scaling up of the technology.The work was possible thanks to a contract with the companies Endesa and Hunosa and to the CaOling project funded by the European Commission FP7. N Rodríguez acknowledges a fellowship awarded by FICYT. The assistance of B González, F Fuentes and I Rodríguez during the experiments and sample analysis is also acknowledged.Peer reviewe

Accurate integration of forced and damped oscillators

The new methods accurately integrate forced and damped oscillators. A family of analytical functions is introduced known as T-functions which are dependent on three parameters. The solution is expressed as a series of T-functions calculating their coefficients by means of recurrences which involve the perturbation function. In the T-functions series method the perturbation parameter is the factor in the local truncation error. Furthermore, this method is zero-stable and convergent. An application of this method is exposed to resolve a physic IVP, modeled by means of forced and damped oscillators. The good behavior and precision of the methods, is evidenced by contrasting the results with other-reputed algorithms implemented in MAPLE

Post-combustion calcium looping process with a high stable sorbent activity by recarbonation

[EN] This paper presents a novel sorbent regeneration technique for post-combustion calcium looping CO2 capture systems. The advantage of this technique is that it can drastically reduce the consumption of limestone in the plant without affecting its efficiency and without the need for additional reagents. The method is based on the re-carbonation of carbonated particles circulating from the carbonator using pure CO2 obtained from the gas stream generated in the calciner. The aim is to maintain the CO2 carrying capacity of the sorbent close to optimum values for CaL post-combustion systems (around 0.2). This is achieved by placing a small regeneration reactor between the carbonator and the calciner. This reactor increases slightly the conversion of CaO to carbonate so that it exceeds the so-called maximum CO2 carrying capacity of the sorbent. This increase compensates for the loss of CO2 carrying capacity that the solids undergo in the next calcination-carbonation cycle. Two series of experiments carried out in a thermogravimetric analyzer over 100 cycles of carbonation-recarbonation-calcination show that the inclusion of this recarbonation step is responsible for an increase in the residual CO2 carrying capacity from 0.07 to 0.16. A conceptual design of the resulting capture system shows that a limestone make-up flow designed specifically for a CO2 capture system can approach zero, when the solid sorbents purged from the CaL system are re-used to desulfurize the flue gas in the existing power plant.We thank the European Commission for the financial support received through the “CaOling” Project, funded under the 7th Framework Programme.Peer reviewe

Heat requirements in a calciner of CaCO3 integrated in a CO2 capture system using CaO

7 pages, 8 figures, 1 table.-- Available online on Jun 12, 2007.Several systems for CO2 capture using CaO as regenerable sorbent are under development. In addition to a carbonation step, they all need a regeneration step (calcination of CaCO3) to produce a concentrated stream of CO2. Different options for calcination may be possible, but they all share common operating windows that appear when the mass and heat balances in the system are solved incorporating equilibrium data, sorbent performance information, and fuel composition (sulphur and ash content). These relatively narrow operating windows are calculated and discussed in this work. Due to sorbent performance limitations, low carbonation levels of the sorbent in the carbonator are expected and the heat demand in the calciner is dominated by the heating of inert solids flowing in the carbonation chemical loop. High make up flows of fresh limestone reduce this effect by increasing the average reactivity of the sorbent, but they also increase the heat demand in the calciner to calcine the fresh feed of limestone. Hence, an optimum level of sorbent activity appears under different operating conditions, processes and fuel characteristic, and these are discussed in this work.This paper contains work from a project partially funded by the European Commission (C3Capture and ISCC projects) and the project CENIT-CO2 in Spain, where we acknowledge funding from Union Fenosa SA. G. Grasa acknowledges a grant under the "Juan de la Cierva" program.Peer reviewe

Side effects of chaperone gene co-expression in recombinant protein production

Insufficient availability of molecular chaperones is observed as a major bottleneck for proper protein folding in recombinant protein production. Therefore, co-production of selected sets of cell chaperones along with foreign polypeptides is a common approach to increase the yield of properly folded, recombinant proteins in bacterial cell factories. However, unbalanced amounts of folding modulators handling folding-reluctant protein species might instead trigger undesired proteolytic activities, detrimental regarding recombinant protein stability, quality and yield. This minireview summarizes the most recent observations of chaperone-linked negative side effects, mostly focusing on DnaK and GroEL sets, when using these proteins as folding assistant agents. These events are discussed in the context of the complexity of the cell quality network and the consequent intricacy of the physiological responses triggered by protein misfolding

El hombre de las cavernas? : Desmantelando un tópico

Jornadas de Jóvenes en Investigación Arqueológica, JIA (3as : 5-7 de mayo 2010 : Universitat Autònoma de Barcelona). Sesión 10. Los tópicos en arqueología. Reflexiones en torno a la mitificación del pasado.Entre los distintos tópicos existentes en el ideario colectivo se encuentra el del "hombre de las cavernas", el cual presupone que la cueva fue el lugar de habitación exclusivo de los grupos de cazadores recolectores del paleolítico. Este artículo está enfocado para rastrear el origen y consolidación de este mito para, en último término, y mediante la evidencia arqueológica, someterlo a un juicio crítico que concluya en su desmantelamiento.The "cave man" is one of the topics that exist nowadays in our colective ideology. It asume that the cave was the exclusive habitat site of the harvester-hunters groups of the paleolithic time. This article is approached in order to look up the origin and consolidation of this myth to, through the archaelogical evidence, submit it to a critical judgement which deny that idea.Entre els diferents tòpics existents en l'ideari col·lectiu es troba el de "l'home de les cavernes", el qual pressuposa que la cova fou el lloc d'habitatge exclusiu dels grups de caçadors recol·lectors del paleolític. Aquest article està enfocat per a rastrejar l'origen I consolidació d'aquest mite per, en ultimo terme, I mitjançant l'evidència arqueològica, sotmetre'l a un judici crític que conclogui en el seu desmantellament

Reciclado de residuos cerámicos en materiales absorbentes acústicos

The scope of this investigation is to develop a material mainly composed (80% w/w) of ceramic wastes that can be applied in the manufacture of road traffic noise reducing devices. The characterization of the product has been carried out attending to its acoustic, physical and mechanical properties, by measuring the sound absorption coefficient at normal incidence, the open void ratio, density and compressive strength. Since the sound absorbing behavior of a porous material is related to the size of the pores and the thickness of the specimen tested, the influence of the particle grain size of the ceramic waste and the thickness of the samples tested on the properties of the final product has been analyzed. The results obtained have been compared to a porous concrete made of crushed granite aggregate as a reference commercial material traditionally used in similar applications. Compositions with coarse particles showed greater sound absorption properties than compositions made with finer particles, besides presenting better sound absorption behavior than the reference porous concrete. Therefore, a ceramic waste-based porous concrete can be potentially recycled in the highway noise barriers field.El objetivo de este trabajo es desarrollar un material absorbente acústico compuesto fundamentalmente por residuos cerámicos (80% p) que se pueda utilizar en la fabricación de dispositivos reductores de ruido de carretera. La caracterización del producto se ha llevado a cabo atendiendo a sus propiedades acústicas, físicas y mecánicas, determinando el coeficiente de absorción acústica a incidencia normal, porosidad abierta, densidad y resistencia a compresión. La absorción acústica de un material poroso está fuertemente determinada por el tamaño de poro y por la longitud dela probeta sometida a ensayo. De este modo, se ha analizado la influencia del tamaño de partícula del residuo cerámico y del espesor de las muestras estudiadas en las propiedades del producto final. Los resultados obtenidos se han comparado con los obtenidos para un hormigón poroso elaborado con árido grueso, que se ha tomado como producto de referencia tradicionalmente empleado en este tipo de aplicaciones. Las composiciones elaboradas con el residuo de mayor tamaño de partícula han mostrado mayor absorción acústica, incluso mayor que las del hormigón poroso comercial. Por tanto, un hormigón poroso elaborado con residuos cerámicos puede ser potencialmente empleado como material en la fabricación de barreras acústicas de carretera

El sociodrama como técnica de intervención socioeducativa.

Sin resume

In silico/in vivo insights into the functional and evolutionary pathway of Pseudomonas aeruginosa oleate-diol synthase. Discovery of a new bacterial di-heme cytochrome C peroxidase subfamily

As previously reported, P. aeruginosa genes PA2077 and PA2078 code for 10S-DOX (10S-Dioxygenase) and 7,10-DS (7,10-Diol Synthase) enzymes involved in long-chain fatty acid oxygenation through the recently described oleate-diol synthase pathway. Analysis of the amino acid sequence of both enzymes revealed the presence of two heme-binding motifs (CXXCH) on each protein. Phylogenetic analysis showed the relation of both proteins to bacterial di-heme cytochrome c peroxidases (Ccps), similar to Xanthomonas sp. 35Y rubber oxidase RoxA. Structural homology modelling of PA2077 and PA2078 was achieved using RoxA (pdb 4b2n) as a template. From the 3D model obtained, presence of significant amino acid variations in the predicted heme-environment was found. Moreover, the presence of palindromic repeats located in enzyme-coding regions, acting as protein evolution elements, is reported here for the first time in P. aeruginosa genome. These observations and the constructed phylogenetic tree of the two proteins, allow the proposal of an evolutionary pathway for P. aeruginosa oleate-diol synthase operon. Taking together the in silico and in vivo results obtained we conclude that enzymes PA2077 and PA2078 are the first described members of a new subfamily of bacterial peroxidases, designated as Fatty acid-di-heme Cytochrome c peroxidases (FadCcp)