Search

This article deals with an inverse problem concerning the identification of the heat exchange coefficient H (assumed depending on the temperature and/or pressure) between a certain material with the external environment, when only experimental measurements of the temperature are supposed to be known. The main difficulties are that we consider the case of functions H depending on the solution of the state equation and we use experimental data that may have errors. We develop rigorous mathematical strategies for this identification. We separately consider pressure and temperature dependence and, in both cases, we set several scenarios for the inverse problem. For each scenario, we know the initial and ambient temperatures, we identify function H through different methods and we obtain error bounds in adequate norms (uniform and square integrable). Finally, we perform numerical tests in order to compare the results obtained with these algorithms and with some classical regularization algorithms. [ABSTRACT FROM AUTHOR]

Activated carbon impregnated with precursor salts of Ba, Co, Cu, Fe, Mg, Mn, Ni, Pb and V and their binary mixtures was used for adsorption of SO2 at 20 °C. The most promising materials for SO2 removal are carbons doped with V, Cu and mainly their binary mixtures, which show a synergetic effect. Kinetic curves and isotherms of SO2 adsorption were obtained at 20 °C. These isotherms are reasonably well fitted by the Langmuir model and the respective parameters were determined. TPD experiments show that adsorption of SO2 increases the oxygenated groups on the carbon surface. The sample doped with V, after SO2 adsorption at 20 °C, presents an increase of basic oxygenated groups, which may be responsible for the observed extra adsorption of SO2. [Copyright &y& Elsevier]

Abstract. We prove the approximate controllability of several nonlinear parabolic boundary-value problems by means of two different methods: the first one can be called a Cancellation method and the second one uses the Kakutani fixed-point theorem. Key Words. Approximate controllability, Semilinear parabolic boundary-value problems, Interior or boundary controls. [ABSTRACT FROM AUTHOR]

Studies the mapping of the porcine peroxisome proliferator activated receptor alpha gene to chromosome 5. Primer sequences; Polymerase chain reaction conditions; Genetic polymorphism and Mendelian inheritance; Chromosomal location.

Alkoxylation of α−pinene, β−pinene and limonene was performed in the presence of SBA-15-occluded tungstophosphoric acid (HPW). The HPW was immobilised in SBA-15 using the sol-gel method. The catalysts were characterised by N 2 adsorption, FT-IR, Raman spectroscopy, X-Ray diffraction, ICP-AES and TEM. A series of catalysts with different heteropolyacid loadings ranging from 1.8 to 19.3 wt. % were prepared. PW4-SBA-15 (with 10.8 wt. %) exhibited the highest catalytic activity for the alkoxylation of α-pinene with ethanol. An approximately 53% selectivity to α-terpinyl ethyl ether was observed over the PW-SBA-15 catalysts. PW4-SBA-15 was also used as a catalyst for the alkoxylation of other terpenes, including β-pinene and limonene. The PW4-SBA-15 catalyst exhibited high catalytic stability for the alkoxylation of α-pinene with ethanol. PW4-SBA-15 was also used as a catalyst for the esterification of free fatty acids (i.e., palmitic, stearic and oleic acids) with ethanol. Good catalytic activity was observed for the PW4-SBA-15 catalyst with the different substrates used in the esterifications. [ABSTRACT FROM AUTHOR]

In this work, we study optimal and suboptimal control strategies for the treatment of a polluted water resource by using aside a continuous bioreactor. The control consists in choosing the inlet volumetric flow rate for filling the bioreactor with contaminated water from a considered resource (lake, reservoir, water-table, …). The treated outflow returns to the resource. We tackle an optimization problem which aims to minimize the time needed to reach a prescribed minimal value of contamination in the resource by choosing the input flow. Next, we study the influence of inhomogeneities of concentrations in the bioreactor, considering a system based on partial differential equations which describe its dynamics. We show that applying the optimal feedback control derived for perfectly mixed bioreactor does not allow to reach the target with small diffusion parameters as it drives the bioreactor to washout (the bioreactor equilibrium with no biomass). In this case, a suboptimal feedback (which reaches the target in finite time) is obtained with the help of a Hybrid Genetic Algorithm. Furthermore, we consider that the fluid flow velocity of the water entering into the bioreactor follows either a uniform or a nonuniform profile, showing that the optimal volumetric flow rates obtained with the uniform profile are not optimal if the profile is nonuniform, even when high diffusion coefficients are considered in the model. [ABSTRACT FROM AUTHOR]

Studies the assignment of the porcine peptide YY gene to chromosome 12. Primer sequences; Polymerase chain reaction conditions; Genetic polymorphism and Mendelian inheritance; Chromosomal location.

Abstract: Nowadays, consumers look for minimally processed, additive-free food products that maintain their organoleptic properties. This has led to the development of new technologies for food processing. One emerging technology is high hydrostatic pressure, as it proves to be very effective in prolonging the shelf life of foods without losing its properties. Recent research has involved modelling and simulating the effect of combining thermal and high pressure processes (see Denys et al. (2000) [3], Infante et al. (2009) [5], Knoerzer et al. (2007) [6], Otero et al. (2007) [9]). The focus is mainly on the inactivation of certain enzymes and microorganisms that are harmful to food. Various mathematical models that study the behaviour of these enzymes and microorganisms during a high pressure process have been proposed (see Infante et al. (2009) [5], Knoerzer et al. (2007) [6]). Such models need the temperature and pressure profiles of the whole process as an input. In this paper we present two dimensional models, with different types of boundary conditions, to calculate the temperature profile for solid type foods. We give an exact solution and propose several simplifications, in both two and one dimensions. The temperature profile of these simplified two and one dimensional models is calculated both numerically and analytically, and the solutions are compared. Our results show a very good agreement for all the approximations proposed, and so we can conclude that the simplifications and dimensional reduction are reasonable for certain parameter values, which are specified in this work. [Copyright &y& Elsevier]

Acetalization of glycerol with hexanal was studied over sulfonic acid-functionalized mesoporous silica (SBA-15), at 70 ºC. The product obtained were (2-pentyl-1,3-dioxolan-4-yl)methanol and 2-pentyl-1,3-dioxan-5-ol. Materials with different amounts of sulfonic acid groups were prepared. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these materials by grafting technique. The [SO 3 H]-SBA-15 catalysts were characterized by nitrogen adsorption at 77 K, X-ray diffraction, SEM and titrations. All the catalysts were active in the studied reaction being the [SO 3 H] 3 -SBA-15 the best one. It was observed that the reaction rate increase with the amount of sulfonic acid groups on SBA-15 until a maximum. With high amounts of sulfonic groups, a decrease of activity is observed. Good values of selectivity to (2-pentyl-1,3-dioxolan-4-yl)methanol were obtained with mesoporous silicas anchored sulfonic acid groups. Catalytic stability of the [SO 3 H] 3 -SBA-15 was evaluated by performing consecutive batch runs with the same catalyst sample. The material showed a good catalytic stabilization. [Display omitted] • Acetalization of glycerol with hexanal was carried out over SBA-15 with sulfonic groups. • High catalytic activity of [SO 3 H] 3 -SBA-15. • Good selectivity to (2-pentyl-1,3-dioxolan-4-yl) methanol product. • Good catalytic activity after the fifth use. [ABSTRACT FROM AUTHOR]

Abstract: The hydrolysis of sucrose into glucose and fructose was carried out over composite catalysts at 80°C. These catalysts consisted of USY and Beta zeolites dispersed in polymeric matrices (PDMS and PVA). The swelling degree of polymers increased with the amount of zeolite immobilised in PDMS and PVA. This result can be explained by the increase in the polymeric matrix channelling. Additionally, the effective diffusivity of sucrose increases with the amount of USY and Beta zeolite that was dispersed in PDMS. The catalytic activity increases with the amount of zeolite dispersed in the polymeric matrix. The PVA composites showed higher catalytic activity than the PDMS ones. To study the catalytic stability of the Beta2/PVA catalyst, four consecutive batch runs were carried out with the same catalyst. The Beta2/PVA catalyst was recycled and reused with a negligible loss in its activity. [Copyright &y& Elsevier]

Abstract: Acetalisation of glycerol with butanal has been investigated over a range of zeolites with different pore structures and acidity (USY with different Si/Al ratio, BEA and ZSM-5). The products of glycerol acetalisation were (Z+E)-(2-propyl-1,3-dioxolan-4-yl) methanol (five-member ring acetal) and (Z+E)-2-propyl-1,3-dioxan-5-ol (six-member ring acetal). The results showed an optimum in activity for Si/Al ratio in USY zeolite that corresponds to 30. BEA zeolite presented the highest catalytic activity of all zeolites while ZSM-5 zeolite presented the lowest activity. All catalysts exhibited high selectivity to five-member ring acetal product (77–82%). The effects of reaction temperature, catalyst loading and molar ratio of glycerol to butanal on this reaction, over BEA zeolite, have been studied. It was found that the glycerol conversion increased with the catalyst loading, with the temperature and with molar ratio of glycerol to butanal. BEA zeolite was recycled four times with the same catalyst sample. It was observed a stabilization of the catalytic activity (after the fourth use, the zeolite showed 93% of its initial activity). [Copyright &y& Elsevier]

Abstract: A new stochastic and spatial model was developed to evaluate the potential spread of classical swine fever virus (CSFV) within- and between-farms, and considering the specific farm-to-farm contact network. Within-farm transmission was simulated using a modified SI model. Between-farm transmission was assumed to occur by direct contacts (i.e. animal movement) and indirect contacts (i.e. local spread, vehicle and person contacts) and considering the spatial location of farms. Control measures dictated by the European legislation (i.e. depopulation of infected farms, movement restriction, zoning, surveillance, contact tracing) were also implemented into the model. Model experimentation was performed using real data from Segovia, one of the provinces with highest density of pigs in Spain, and results were presented using the mean, 95% probability intervals [95% PI] and risk maps. The estimated mean [95% PI] number of infected, quarantined and depopulated farms were 3 [1,17], 23 [0,76] and 115 [0,318], respectively. The duration of the epidemic was 63 [26,177] days and the most important way of transmission was associated with local spread (61.4% of the infections). Results were consistent with the spread of previous CSFV introductions into the study region. The model and results presented here may be useful for the decision making process and for the improvement of the prevention and control programmes for CSFV. [ABSTRACT FROM AUTHOR]

Abstract: The acetalisation of glycerol was studied using heteropolyacids, immobilized in silica, as catalysts, at 70°C. The main product of glycerol acetalisation was solketal. The tungstophosphoric (PW), molybdophosphoric (PMo), tungstosilisic (SiW) and molybdosilisic (SiMo) acids were immobilized in silica by sol–gel method. It was observed that the catalytic activity decreases in the series: PW_S>SiW_S>PMo_S>SiMo_S. All catalysts exhibited good values of selectivity to solketal (about 98% near complete conversion). The effect of different parameters, such as catalyst loading, molar ratio of glycerol to acetone and temperature on the glycerol acetalisation, over PW_S catalyst, was studied. Catalytic stability of the PW_S, SiW_S, PMo_S and SiMo_S catalysts was evaluated by performing consecutive batch runs with the same catalyst sample. After the third batch, it was observed a stabilisation of the initial activity. [Copyright &y& Elsevier]

Abstract: Vanadia-titania catalysts prepared by different sol–gel procedures were studied as heterogeneous catalysts for the liquid phase oxidation of limonene. The catalysts were characterized by XRD, XPS, ICP and nitrogen adsorption. According to the XRD results the catalyst samples can be divided in two different groups: anatase samples and anatase+rutile samples. XRD signals of vanadia are not found in the diffractograms. The main reaction products are polymers. Limonene oxide, limonene glycol, carveol and carvone are obtained in small amounts. A number of autoxidation products, alcohols, aldehydes and ketones, are also obtained. The effects of titania composition on the reaction orientation are discussed. [Copyright &y& Elsevier]

The mechanical properties of bacterial polyhydroxyalkanoates (PHAs) can be tailored by changing the type of substrate in the accumulation stage. Hence different comonomer distributions can be produced with significant variations in their physico-chemical properties. In the present study, the biopolymer produced by a mixed microbial community enriched in PHA accumulators fed with different substrate composition was characterised. The accumulation experiments were: single acetic (A1) and propionic acids (A2); an equivolumetric mixture of acetic and propionic acids (A3); VFA mixture (A4); and this VFA mixture and a concentration of 21.6 g NaCl/L in the reactor (B1). The objective was to investigate the impact of different circumstances on biopolymer composition and properties. The obtained copolymers were constituted by units of hydroxybutyrate (HB) and hydroxyvalerate (HV) with HB:HV ratios between 96:4 and 34:66 (wt%). Thermal properties showed a clear dependence on the HB:HV ratio although no apparent connection with the decomposition temperature was found. Salinity affected both biopolymer composition and properties. The physico-chemical properties of purified and no purified polymer were also determined. Purification was found not to affect the molecular weight, while crystallinity augmented more than 70% and the thermal properties also increased. This study shows that, besides the substrate composition, also salts present in the media and the purification stage affect the properties of the produced biopolymer. [ABSTRACT FROM AUTHOR]