Showing papers by "University of Extremadura published in 2003"

Ozone Reaction Kinetics for Water and Wastewater Systems

Abstract: INTRODUCTION Ozone in Nature The Ozone Molecule REACTIONS OF OZONE IN WATER Oxidation-Reduction Reactions Cycloaddition Reactions Electrophilic Substitution Reactions Necleophilic Reactions Indirect Reactions of Ozone KINETICS OF THE DIRECT OZONE REACTIONS Homogenous Kinetecs Heterogenous Kinetics FUNDAMENTALS OF GAS-LIQUID REACTION KINETICS Physical Absorption Chemical Absorption KINETIC REGIMES IN DIRECT OZONATION REACTIONS Determination of Ozone Properties in Water Kinetic Regimes of the Ozone Decomposition Reaction Kinetic Regimes of Direct Ozonation Reactions Changes of the Kinetic Regimes During Direct Ozonation Reactions Comparison Between Absorption Theories in Ozonation Reactions KINETCS OF THE OZONATION OF WASTEWATERS Reactivity of Ozone in Wastewater Critical Concentration of Wastewater Characterization of Wastewater Importance of pH in Wastewater Ozonation Chemical Biological Processes Kinetic Study of the Ozonation of Wastewaters KINETICS OF INDIRECT REACTIONS OF OZONE IN WATER Relative Importance of the Direct Ozone-B Reaction and the Ozone Decomposition Reaction Relative Rates of the Oxidation of a Given Compound Kinetic Parameters Characterization of Natural Waters Regarding Ozone Reactivity KINETICS OF THE OZONE/HYDROGEN PEROXIDE SYSTEM The Kinetic Regime of the O3/H2O2 Process Determination of Kinetic Parameters The Ozone/Hydrogen Peroxide Oxidation of Volatile Compounds The Competition of the Direct Reaction KINETICS OF THE OZONE-UV RADIATION SYSTEM Kinetics of the UV Radiation for the Removal of Contaminants from Water Kinetics of the UV/H2O2 System Comparison between the Kinetic Regimes of the Ozone-B and Ozone-UV Photolysis Reactions HETEROGENEOUS CATALYTIC OZONATION Fundamentals of Gas-Liquid-Solid Catalytic Reaction Kinetics Kinetics of Heterogeneous Catalytic Ozone Decomposition in Water Kinetics of Heterogeneous Catalytic Ozonation of Compounds in Water Kinetics of Semiconductor Photocatalytic Processes KINETIC MODELLING OF OZONE PROCESSES Case of Slow Kinetic Regime of Ozone Absorption Case of Fast Kinetic Regime of Ozone Absorption Case of Intermediate or Moderate Kinetic Regime of Ozone Absorption Time Regimes in Ozonation Influence of the Type of Water and Gas Flows Mathematical Models Examples of Kinetic Modeling for Model Compounds Kinetic Modeling of Wastewater Ozonation Appendixes

STELIB: A library of stellar spectra at R 2000 ?;??

Abstract: We present STELIB ? , a new spectroscopic stellar library, available at http://webast.ast.obs-mip.fr/stelib. STELIB consists of an homogeneous library of 249 stellar spectra in the visible range (3200 to 9500 A), with an intermediate spectral resolution (<3 A) and sampling (1 A). This library includes stars of various spectral types and luminosity classes, spanning a relatively wide range in metallicity. The spectral resolution, wavelength and spectral type coverage of this library represents a substantial improvement over previous libraries used in population synthesis models. The overall absolute photo- metric uncertainty is 3%.

Two direct Tustin discretization methods for fractional-order differentiator/integrator

Abstract: This paper deals with fractional calculus and its approximate discretization. Two direct discretization methods useful in control and digital filtering are presented for discretizing the fractional-order differentiator or integrator. Detailed mathematical formulae and tables are given. An illustrative example is presented to show the practically usefulness of the two proposed discretization schemes. Comparative remarks between the two methods are also given.

Serotypes, Virulence Genes, and Intimin Types of Shiga Toxin (Verotoxin)-Producing Escherichia coli Isolates from Healthy Sheep in Spain

Abstract: Fecal swabs obtained from 1,300 healthy lambs in 93 flocks in Spain in 1997 were examined for Shiga toxin-producing Escherichia coli (STEC). STEC O157:H7 strains were isolated from 5 (0.4%) animals in 4 flocks, and non-O157 STEC strains were isolated from 462 (36%) lambs in 63 flocks. A total of 384 ovine STEC strains were characterized in this study. PCR showed that 213 (55%) strains carried the stx(1) gene, 10 (3%) possessed the stx(2) gene, and 161 (42%) carried both the stx(1) and the stx(2) genes. Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 106 (28%) and 23 (6%) of the STEC strains, respectively. The STEC strains belonged to 35 O serogroups and 64 O:H serotypes (including 18 new serotypes). However, 72% were of 1 of the following 12 serotypes: O5:H-, O6:H10, O91:H-, O117:H-, O128:H-, O128:H2, O136:H20, O146:H8, O146:H21, O156:H-, O166:H28, and ONT:H21 (where NT is nontypeable). Although the 384 STEC strains belonged to 95 different seropathotypes (associations between serotypes and virulence genes), 49% of strains belonged to only 11. O91:H- stx(1) stx(2) (54 strains) was the most common seropathotype, followed by O128:H- stx(1) stx(2) (33 strains) and O6:H10 stx(1) (25 strains). Three strains of serotypes O26:H11, O156:H11, and OX177:H11 had intimin type beta1; 5 strains of serotype O157:H7 possessed intimin type gamma1; and 15 strains of serotypes O49:H-, O52:H12, O156:H- (12 strains), and O156:H25 had the new intimin, intimin type zeta. The majority (82%) of ovine STEC strains belonged to serotypes previously found to be associated with human STEC strains, and 51% belonged to serotypes associated with STEC strains isolated from patients with hemolytic-uremic syndrome. Thus, this study confirms that healthy sheep are a major reservoir of STEC strains pathogenic for humans.

Effects of land-use history on size structure of holm oak stands in Spanish dehesas: implications for conservation and restoration

Abstract: Dehesas, rangelands occupied by scattered oak trees and characterized by silvopastoral uses, cover about 3.1 million ha in south-western Spain. There is considerable debate about the long-term persistence of holm oak (Quercus ilex) populations in dehesas, since most stands are overaged and seedlings and saplings are sparse. The forest cycle has been disrupted in most dehesas. Regeneration has been inhibited since stands were opened for agriculture and grazing. Oak diameters from three land-use groups (young dehesa [YD], middle-aged dehesa [MD], and old dehesa [OD]) in Caceres Province, Spain, were compared. These groups differed in the age of the land-use system, i.e. time since the original Mediterranean forest was cleared. The dehesa systems were established about 80 (YD), 150 (MD) and 500 (OD) years ago. An analysis of 66 holm oak cross sections revealed a close correlation (r2 = 91.2%) between tree rings and diameters, so that diameter seems to be a reliable indicator of tree age. Nested analysis of variance showed significant variation in diameters between the land-use groups. There is generally a positive relationship between tree age and the age of agrosilvopastoral use of the dehesas. Sparse holm oaks in the dehesas are primarily remnants from the first forest cycle. Local differences in growth conditions (for example soil quality and tree density) contribute further significant diameter variation on a between-plot level. Diameter structure of abandoned dehesas showed two peaks and a high proportion of trees in the smallest size class. This indicates that the forest degradation process is reversible. An effective regeneration policy should promote a rotating 20- to 30-year set-aside of dehesa parcels.

An Empirical Study of Multipopulation Genetic Programming

Abstract: This paper presents an experimental study of distributed multipopulation genetic programming. Using three well-known benchmark problems and one real-life problem, we discuss the role of the parameters that characterize the evolutionary process of standard panmictic and parallel genetic programming. We find that distributing individuals between subpopulations offers in all cases studied here an advantage both in terms of the quality of solutions and of the computational effort spent, when compared to single populations. We also study the influence of communication patterns such as the communication topology, the number of individuals exchanged and the frequency of exchange on the evolutionary process. We empirically show that the topology does not have a marked influence on the results for the test cases studied here, while the frequency and number of individuals exchanged are related and there exists a suitable range for those parameters which is consistently similar for all the problems studied.

Urinary bladder instability induced by selective suppression of the murine small conductance calcium-activated potassium (SK3) channel.

Abstract: Small conductance, calcium-activated potassium (SK) channels have an important role in determining the excitability and contractility of urinary bladder smooth muscle. Here, the role of the SK isoform SK3 was examined by altering expression levels of the SK3 gene using a mouse model that conditionally overexpresses SK3 channels (SK3T/T). Prominent SK3 immunostaining was found in both the smooth muscle (detrusor) and urothelium layers of the urinary bladder. SK currents were elevated 2.4-fold in isolated myocytes from SK3T/T mice. Selective suppression of SK3 expression by dietary doxycycline (DOX) decreased SK current density in isolated myocytes, increased phasic contractions of isolated urinary bladder smooth muscle strips and exposed high affinity effects of the blocker apamin of the SK isoforms (SK1-3), suggesting an additional participation from SK2 channels. The role of SK3 channels in urinary bladder function was assessed using cystometry in conscious, freely moving mice. The urinary bladders of SK3T/T had significantly greater bladder capacity, and urine output exceeded the infused saline volume. Suppression of SK3 channel expression did not alter filling pressure, threshold pressure or bladder capacity, but micturition pressure was elevated compared to control mice. However, SK3 suppression did eliminate excess urine production and caused a marked increase in non-voiding contractions. The ability to examine bladder function in mice in which SK3 channel expression is selectively altered reveals that these channels have a significant role in the control of non-voiding contractions in vivo. Activation of these channels may be a therapeutic approach for management of non-voiding contractions, a condition which characterizes many types of urinary bladder dysfunctions including urinary incontinence.

Analysis of Volatiles in Meat from Iberian Pigs and Lean Pigs after Refrigeration and Cooking by Using SPME-GC-MS

Abstract: The volatile compounds generated in meat from Iberian and lean pigs after four different treatments (raw, refrigerated, cooked, and refrigerated cooked meat) were analyzed. The different treatments showed different volatile profiles. Methyl alcohols and ketones (such as 2-ethyl-hexan-1-ol, 2-methyl-butan-1-ol, 3-methyl-butan-1-ol, and 3-hydroxy-butan-2-one) were the most representative in refrigerated meat because of the degradation of carbohydrates and proteins together with the Strecker degradation pathway. Lipid-derived volatiles were the most abundant in cooked meat and refrigerated cooked meat. Meat from different pig breeds presented different volatile profiles, probably due to different enzymatic and oxidative deterioration susceptibility. Otherwise, the fat content and its compositional characteristics also played an important role in the generation of volatiles. As compared to samples from lean pigs, muscles from Iberian pigs showed a higher content of heme iron that may have promoted the generation of higher content of total lipid-derived volatiles during the refrigeration of cooked meat. Despite that, the formation of volatiles with low thresholds and related to intense rancidity perception likely to be derived from polyunsaturated fatty acids was higher in lean pork than in meat from Iberian pigs. This might be expected to lead to a more intense development of a warmed over flavor during refrigeration of cooked samples from lean pigs.

Ozone-Enhanced Oxidation of Oxalic Acid in Water with Cobalt Catalysts. 2. Heterogeneous Catalytic Ozonation

Abstract: Ozone and a Co3O4/Al2O3 catalyst have been used to remove oxalic acid from water at acidic pH. The influence of different variables, including the initial oxalic acid and ozone gas concentrations, the catalyst mass, and the temperature, has been investigated under conditions of chemical control. The ozone efficiency was found to reach values of up to 40%, which are higher than those found in homogeneous catalysis (see also the first part of this work, which immediately precedes this paper in this issue), and the mean stoichiometry was determined to be 0.8 mol of ozone consumed per mole of oxalic acid consumed. Metal leaching was also followed to check the stability of the catalyst. As a result, ozonation of oxalic acid was found to be due to both heterogeneous and homogeneous catalytic ozonation. The average contribution of heterogeneous catalytic ozonation for the removal of oxalic acid was found to be 75%. A kinetic study taking into account both catalytic contributions is also presented. The experiment...

Activated carbon adsorption of some phenolic compounds present in agroindustrial wastewater

Abstract: Single solute and simultaneous experimental adsorption isotherms of three phenolic compounds: gallic acid, p-hydroxybenzoic acid and syringic acid, have been investigated at 20, 30 and 40°C, using a bituminous coal based activated carbon. Regardless of temperature, the capacity of the activated carbon used to adsorb these compounds presented the following order: syringic acid > p-hydroxybenzoic acid > gallic acid. The increase of temperature slightly favored the adsorption capacity of the phenolic compounds. In binary and ternary component adsorption, experimental data suggest that interactions between adsorbates improve the adsorption capacity of some of the phenolic acid compounds. On the contrary, at high organic concentrations, adsorbed gallic acid was partially removed from the activated carbon surface because of the presence of the other components.

Verotoxin-producing Escherichia coli in Spain: prevalence, serotypes, and virulence genes of O157:H7 and non-O157 VTEC in ruminants, raw beef products, and humans.

Abstract: In Spain, as in many other countries, verotoxin-producing Escherichia coli (VTEC) strains have been frequently isolated from cattle, sheep, and foods. VTEC strains have caused seven outbreaks in Spain (six caused by E. coli O157:H7 and one by E. coli O111:H- [nonmotile]) in recent years. An analysis of the serotypes indicated serological diversity. Among the strains isolated from humans, serotypes O26:H11, O111:H-, and O157:H7 were found to be more prevalent. The most frequently detected serotypes in cattle were O20:H19, O22:H8, O26:H11, O77:H41, O105:H18, O113:H21, O157:H7, O171:H2, and OUT (O untypeable):H19. Different VTEC serotypes (e.g., O5:H-, O6:H10, O91:H-, O117:H-, O128:H-, O128:H2, O146:H8, O146:H21, O156:H-, and OUT:H21) were found more frequently in sheep. These observations suggest a host serotype specificity for some VTEC. Numerous bovine and ovine VTEC serotypes detected in Spain were associated with human illnesses, confirming that ruminants are important reservoirs of pathogenic VTEC. VTEC can produce one or two toxins (VT1 and VT2) that cause human illnesses. These toxins are different proteins encoded by different genes. Another virulence factor expressed by VTEC is the protein intimin that is responsible for intimate attachment of VTEC and effacing lesions in the intestinal mucosa. This virulence factor is encoded by the chromosomal gene eae. The eae gene was found at a much less frequency in bovine (17%) and ovine (5%) than in human (45%) non-O157 VTEC strains. This may support the evidence that the eae gene contributes significantly to the virulence of human VTEC strains and that many animal non-O157 VTEC strains are less pathogenic to humans.

Cambio didáctico del profesorado de ciencias experimentales y filosofía de la ciencia

Abstract: La comprension de los procesos de cambio didactico del profesorado, asi como los aspectos que lo facilitan u obstaculizan, es uno de los temas mas relevantes de la agenda internacional de investigacion educativa, y un elemento esencial para planificar y llevar a cabo programas de formacion inicial y permanente del profesorado. En el articulo revisamos las investigaciones sobre el cambio didactico del profesorado de ciencias experimentales. Para organizar esta informacion establecemos una analogia con el proceso de cambio cientifico, segun distintas teorias de la filosofia de la ciencia, analizando y valorando las aportaciones de los distintos modelos.

CYP1A2 activity, gender and smoking, as variables influencing the toxicity of caffeine.

Abstract: We have investigated several factors that might be related to the occurrence of toxic effects during the performance of a urinary test with caffeine (300 mg p.o.), in 120 healthy volunteers. A total of 218 toxic effects were self-reported by eighty-two (68%) subjects. Females and nonsmokers were at the highest risk (chi-square test, P = 0.01). Furthermore, two nonsmoking females experienced a symptomatology with delirium, restlessness, muscle tremor, vomiting and wakefulness. Among females and nonsmokers, those subjects who experienced toxic effects had lower caffeine N3-demethylation index (CYP1A2 activity) compared with unaffected females (1.87 +/- 0.51 vs 1.47 +/- 0.27, P < 0.0005) and nonsmokers (1.69 +/- 0.23 vs 1.49 +/- 0.31, P < 0.02). Caffeine N1- and N7-demethylations indices were also lower among females (P < 0.0005) and nonsmokers (P < 0.02) who reported toxic symptoms. We conclude that CYP1A2 activity, gender and smoking are variables to be considered as influencing the toxicity of caffeine.

Effect of Smoke, Charred Wood, and Nitrogenous Compounds on Seed Germination of Ten Species from Woodland in Central-Western Spain

Abstract: The effect of smoke, charred wood, and nitrogenous compounds on germination was tested on 10 species of the Cistaceae, Poaceae, Fabaceae, and Asteraceae, from fire-prone, shrubby woodlands in central-western Spain. Dry seeds were exposed to smoke, by watering with distilled water-charred wood suspensions, or NaNO2, KNO3, NH4Cl, and NH4NO3. Smoke enhanced germination in 9 of 10 of the species. In species of Poaceae, germination was stimulated by 20 min of smoke exposure. In Asteraceae and Fabaceae species, 10 min of smoke exposure was the most effective treatment for enhancing germination. Three species--Cistus ladanifer, Cistus crispus, and Cistus monspeliensis--had a positive response to 20 min of smoke exposure; germination of Cistus salviifolius L. was also enhanced after 10 min. The effect of charred wood was variable, with no consistent germination pattern within the families. Trifolium angustifolium and Retama sphaerocarpa showed no stimulation of germination under most of the charred wood concentrations. Similarly, germination of Senecio jacobea under the charred wood treatment did not surpass that of the control. NaNO2 promoted seed germination in Dactylis glomerata (10 mM), Cistus ladanifer (1, 10, and 25 mM), and Cistus crispus (1 and 10 mM). KNO3 enhanced germination in Dactylis glomerata (1 and 25 mM), Dittrichia viscosa (10 and 25 mM), C. ladanifer (1, 10, and 25 mM), Cistus crispus (1 and 25 mM), and C. salviifolius aud C. monspeliensis (25 mM). NH4Cl induced germination of Dactylis glomerata and Dittrichia viscosa (1 mM), and Cistus species germinated best in 25 mM of this salt. NH4NO3 induced germination only in Cistus species. Holcus lanatus had the highest level of germination regardless of treatment.

CYP2C9 genotypes and diclofenac metabolism in Spanish healthy volunteers.

Abstract: Objective This study analyzed the frequency of CYP2C9 variant alleles and evaluated the impact of CYP2C9 genotype on diclofenac metabolism in a Spanish population.

Neuroendocrine mediators in the modulation of phagocytosis by exercise: physiological implications.

Abstract: Neuroendocrine mediation of the effects of exercise on macrophage and neutrophil phagocytosis, the organism's first line of defense against external aggression, is reviewed. Exercise modulates the immune system via the actions of "stress hormones". Although stress had long been regarded as generally immunosuppressive, it is now accepted that this is not always true. Indeed exercise-induced stress stimulates the "phagocytic process" of phagocytes. One of the new physiological interpretations emerging from recent studies is that the general stimulation of phagocytosis and other innate mechanisms during strenuous physical activity may counterbalance the decreased lymphoid activity, preventing the entry and survival of microorganisms in situations where the specific responses are depressed. In some cases this behaviour is also medicated by "stress hormones", unlike in lymphocytes in which glucocorticoids and catecholamines both are immunosuppressive. The mediatory role of glucocorticoids in macrophages may also differ between the non-specific functions, like chemotaxis and phagocytosis, and the more specific ones, like antigen-presentation. Neutrophils and monocytes may be stimulated by catecholamines or sympathetic signals, and variations in phagocytosis and catecholamines have been proposed as a good "neuroimmuno-endocrinological marker" in athletes. Other hormones (prolactin, GH, endorphins, thyroid hormones) in general also contribute to the effects of exercise-stress on phagocytosis. This review focuses on a physiological interpretation of the immune response to exercise which differs markedly from the classical immunosuppression-centered view. More studies on in vivo variations of stress hormones during exercise are needed.

Stochastic optimal control of annuity contracts

Abstract: The purpose of this paper is to show how stochastic optimal control theory can be applied to find an optimal investment policy before and after retirement in a defined contribution pension plan where benefits are paid under the form of annuities; annuities are supposed to be guaranteed during a certain fixed period of time. Using different kinds of utility functions we try to look at different strategies on the one hand in the investment part (i.e. before retirement) and on the other hand in the payment part (i.e. after retirement). The needed change of strategy after retirement can be interpreted in this model as a typical ALM constraint taking into account a guaranteed technical interest rate used by the insurer.

Análisis pormenorizado de los grados de burnout y técnicas de afrontamiento del estrés docente en profesorado universitario

Abstract: In this study the different degrees of burnout and stress-management techniques are compared. The aim is to see if there is a relation between the levels of burnout and the different stress-management techniques which are adopted by teachers. Maslach’s Inventory (Maslach and Jackson, 1986) or M.B.I. and the evaluation scale of stressmanagement or C.O.P.E. (Carver, Scheier and Weintraub, 1989) were used in the study. Certain results show that teachers who suffer from a high degree of emotional exhaustion use techniques involving emotional unburdening, behavioural disconnection, drug-taking and acceptance of the situation (passive techniques) On the other hand, those teachers who show a high degree of personal attainment use techniques involving active confrontation, planning, seeking instrumental and social help, having a positive view of the situation and decreasing confrontational situations (active techniques)