Effect of Mn and Cr additions on kinetics of recrystallization and parameters of grain-boundary relaxation of Al-4.9Mg alloy

Methods of microstructural analysis, measurements of hardness, and temperature and time dependences of internal friction (TDIF and TDIF(iso), respectively) have been used to study recrystallization in cold-rolled alloys and grain-boundary relaxation in annealed alloys. A complex analysis of the effect of additions of transition metals (Mn, Cr) on the magnitude of the activation energy of the background of the internal friction in deformed and annealed states and on the activation parameters of grain-boundary relaxation has been performed. Methods of amplitude dependences of internal friction (ADIF) have been used to determine the critical amplitude that corresponds to the beginning of microplastic deformation in the alloys at different temperatures.     

A computational modeling for real ecosystems based on P systems

In this paper, a P systems based general framework for modeling ecosystems dynamics is presented. Particularly, ecosystems are specified by means of multienvironment P systems composed of a finite number of environments, each of them having an extended P system with active membranes. The semantics is of a probabilistic type and it is implemented by assigning each rule of the system a probabilistic constant which depends on the environment and the run time. As a case study, two real ecosystems are described: scavenger birds in the Catalan Pyrenees and the zebra mussel (Dreissena Polymorpha) in Ribarroja reservoir (Spain).     

Computer training, frequency of usage and burnout: the moderating role of computer self-efficacy

The main aim of this paper is to test the moderating role of computer self-efficacy in the relationship among computer training, frequency of usage and burnout (i.e. exhaustion and cynicism). The sample was made up of 140 workers using computer-aided technology in their jobs. Hierarchical multiple regression analyses were carried out. Results show that frequency of usage and computer training are positively associated with computer self-efficacy. Futhermore, we found interaction effects between computer training×computer self-efficacy on both indicators of burnout as outcomes. Computer self-efficacy moderated the relationship between computer training and burnout. Limitations of the study and practical implications of these findings are discussed.     

Resistant Mycobacterium tuberculosis: its relation with coinfection with human immunodeficiency virus. 5-year study

BACKGROUND: To analyze the situation of resistance to antituberculous drugs among strains of Mycobacterium tuberculosis recovered in our environment during a five-year period and its relationship with HIV co-infection. PATIENTS AND METHODS: Review of the Mycobacterium tuberculosis strains recovered from patients aged older than 14 years in Hospital Joan March from 1992 to 1996 of which a susceptibility testing study by means of the multiple proportions method was available. The initial or secondary resistance was considered according to the previous antituberculosis treatment antecedent. RESULTS: The susceptibility testing was available from 179 cases (136 males and 43 females) out of a total of 214. The overall resistance rate to any of the tested drugs was 10.1% (18 cases) with a 4% (6 cases) of initial and 38.7% (12 cases) secondary resistances. Co-infection with HIV showed not to be a risk factor for the development of resistance. No significant increase was observed analyzing the temporal trend through the five years studied. CONCLUSIONS: At present, the situation of resistance to Mycobacterium tuberculosis seems not to be alarming in our environment. Co-infection with HIV has not been shown to be associated with an increase in resistance rates.     

Ionic strength effect in polyelectrolyte dilute solutions within the Debye–Hückel approximation: Monte Carlo and Brownian dynamics simulations

Two chain models, a Gaussian chain and a touching-beads (wormlike) chain, are used to represent a flexible polyelectrolyte (sodium polystyrene sulfonate) and a semiflexible polyelectrolyte (sodium alginate), respectively. Monte Carlo and Brownian dynamics simulations of those models were carried out to obtain the ionic strength dependence of some conformational and hydrodynamic properties expressed in form of equivalent radii. Electrostatic interactions were taken into account by the Debye–Hückel potential, thus counterions are not considered explicitly. In the case of the sodium polystyrene sulfonate model, a linear dependence of the equivalent radii with the ionic strength is found for a region of intermediate to low enough ionic strength values, whereas for high values of the ionic strength the equivalent radii reach a plateau with a value equal to that of the uncharged chain. Thus, an extrapolation to infinite ionic strength of the linear region would not report the actual property value of the uncharged chain. In the case of the sodium alginate model such a linear dependence is not so clearly appreciated. Our simulation results show a good agreement with several experimental data which support the validity of the Debye–Hückel approximation to model different types of polyelectrolyte solutions in a simple way.     

Fatty acid profile,physiochemical properties and oxidative stability of ewe’s sausage as affected by distillated myrtle (Myrtus communis) leaves’ intake

The effects of distilled myrtle leaves (DML) intake on physiochemical traits, fatty acid profile and lipid oxidation of ewe’s sausage (Merguez) were investigated. Twenty-seven ewes were divided into three homogenous groups. Ewes were fed hay and concentrate for control group (C). They received concentrate and M-Hay pellets, containing 87% DML, as substitute to hay in MH group; for MC group, ewes received hay, concentrate and M-Conc pellets having 30% DML in partial substitution to concentrate. They were slaughtered at the end of trial (90 days) with an average body weight of 42 kg. DML did not affect the physicochemical and sensory properties (P > 0.05) of Merguez; whereas, it increased lipid oxidative stability (P < 0.05). MH group showed the highest values of α-tocopherol content, C18:2-n6 fatty acid and polyunsaturated fatty acids. DML could be used in animal feeding to obtain higher meat product quality with better fatty acids content and antioxidant potential.