Surface modification of polyethylene terephthalate (PET) by corona discharge plasma

Surface modification of polyethylene terephthalate (PET) was studied by corona discharge plasma at different exposure times using air as working gas. The modification of the surface properties are characterized, those are morphology and wettability. Corona plasma treatment was found to modify the PET surface in both morphology and wettability. The corona discharge at atmospheric pressure is a heterogeneous with multiple current pulses, which generates an asymmetric pattern of erosion on the PET surface. The corona discharge treatment erodes the surface and therefore modifies the surface morphology. The roughness of the PET surface increases in the impact point of the corona discharge on the PET surface. An increase in the wettability of PET was also observed after corona discharge treatment at atmospheric pressure

Rubber Additions into Concrete and Gamma Radiation Effects on Mechanical Properties and Microwave Absorption Capacity

Rubber is the indispensable raw material for the manufacture of tires; it is obtained from plants, trees and currently can be produced synthetically. The tire rubber is mixed with compounds such as carbon black, sulfur, cement, paints, antioxidants, oils and fats, steel wire, almost etc., making impossible to recycle the tires itself. In this work, we investigate, the effects of the incorporation of ground rubber in concrete, mixture designed to establish the possibility of being used in the construction industry. The samples of concrete were addition with, 5 vol. %., 15 vol. % and 25 vol. % of rubber. Samples with different rubber addition were irradiated by a cobalt 60 gamma source to study the effect on their mechanical compression properties and microwave absorption capacity. Likewise, the microwave absorption capacity was studied for both irradiated and the non-irradiated. It was found that between 5 vol. % and 15 vol. % of rubber addition change the mechanical properties approximately 25 %, higher rubber additions result in a decrease in a 75 % of its mechanical properties. The fracture behavior is not the expected one due to as the curves of stress vs. strain show a double slope, which is associated with the concrete porosity and rubber content. The aging with the gamma rays generates loss of mechanical properties, especially at lower rubber addition, since at content greater than 15 Vol % the radiation effect is less. These rubber additions allow moderate deformations in compression, thus contributing to the care and preservation of the environment

Study of H2/N2Mixture Plasma Treatment on the AISI 1045

In the present work, we analyzed the effect of the plasma treatment of 80% H2/20% N2 mixture plasma over the AISI 1045 steel. To produce the plasma, an AC discharge of 0.1 A at 350 V was produced at a total pressure of 3.0 Torr. The mixture plasma was analyzed using optical emission spectroscopy (OES), in the wavelength range of 200 to 1100 nm. The principal species observed in the plasma were NH, N2, N2+, H2, and Hα. The electron temperature and ion density have been measured using a double Langmuir probe. The samples of steel were treated by plasma at different discharge times, between 3 and 12 h, at the same pressure and AC parameters (0.1 A and 350 V). The treated samples were characterized using X-ray analysis, finding the phases gamma and epsilon of iron nitride. The thickness of the nitrided layers was measured using a scanning electron microscope (SEM). From the images obtained, it is possible to appreciate the interphase between the nitrided layer and the steel matrix. The relationship between the morphology of the surface of nitrided steel and the wetting was analyzed by measuring the contact angle between the surface and a drop of 5 μL of distilled water. The contact angle of the drop increased with the increase of plasma treatment time. The control sample without treatment presented a smaller angle, and after the treatment the surfaces of the steel became hydrophobic. This may be related to the morphology change of the steel surface produced by plasma treatment

Gamma Radiation Doses Effects on Mechanical Properties and Microwave Absorption Capacity of Rubber Doped Concrete

The main raw material for the construction industry is concrete; whose fundamental components are the fine and coarse aggregates, water and cement. For the obtaining of these materials are necessary activities that generate environmental deterioration, since the aggregates are extracted from quarries or river banks and for each ton made of cement is emitted into the atmosphere a great lot of carbon dioxide. In this way, the present work is developed with the purpose of contributing to the research that can help the conservation of basic natural resources through the use of waste polymers such as waste tire rubber, in the production of concrete, hoping to reduce its harmful environmental impact. This work focuses on the one hand, in the study of the effects of the incorporation to the concrete, of different proportions of scratched rubber coming from waste tires, on its mechanical properties and on its capacity for microwaves absorption. On the other hand, it is also studied the effect of aging by applying different doses of gamma radiation on the before mentioned properties, seeking with this the possibility that it can be used in the construction industry either as structural material or as a coating. Replacements were made between 5% and 25% of rubber in order to do not significantly affecting the mechanical properties of the concrete. The results of the mechanical and microwave tests performed on the different samples with different gamma radiation doses were compared and it was found that open the possibility of research with great benefits such as the use of waste tires in the designing of concrete mixtures and the improvement of its properties. It is considered important to point out the economic benefit in the context of sustainable development, which involves solving the problem of environmental pollution caused by waste tires, to achieve the welfare of the population by improving their quality of life

In the quest of specific-domain ontology components for the semantic web

This paper describes an approach we have been using to identify specific-domain ontology components by using Self-Organizing Maps. These components are clustered together in a natural way according to their similarity. The knowledge maps, as we call them, show colored regions containing knowledge components that may be used to populate an specific-domain ontology. Later, these ontology may be used by software agents to carry out basic reasoning task on our behalf. In particular, we deal with the issue of not constructing the ontology from scratch, our approach helps us to speed up the ontology creation process

Relationship between serotypes, age, and clinical presentation of invasive pneumococcal disease in Madrid, Spain, after introduction of the 7-valent pneumococcal conjugate vaccine into the vaccination calendar

To assess invasive pneumococcal disease (IPD) clinical presentations and relationships with age and serotype in hospitalized children (<15 years) after PCV7 implementation in Madrid, Spain, a prospective 2-year (May 2007 to April 2009) laboratory-confirmed (culture and/or PCR) IPD surveillance study was performed (22 hospitals). All isolates (for serotyping) and culture-negative pleural/cerebrospinal fluids were sent to the reference laboratory for pneumolysin (ply) and autolysin (lyt) gene PCR analysis. A total of 330 IPDs were identified: 263 (79.7%) confirmed by culture and 67 (20.3%) confirmed by PCR. IPD distribution by age (months) was as follows: 23.6% (<12), 15.8% (12 to 23), 15.5% (24 to 35), 22.4% (36 to 59), and 22.7% (>59). Distribution by clinical presentation was as follows: 34.5% bacteremic pneumonia, 30.3% pediatric parapneumonic empyema (PPE), 13.6% meningitis, 13.3% primary bacteremia, and 8.2% others. Meningitis and primary bacteremia were the most frequent IPDs in children <12 months old, and bacteremic pneumonia and PPE were most frequent in those >36 months old. Frequencies of IPD-associated serotypes were as follows: 1, 26.1%; 19A, 18.8%; 5, 15.5%; 7F, 8.5%; 3, 3.9%; nontypeable/ other 30 serotypes, 27.3%. Serotype 1 was linked to respiratory-associated IPD (38.6% in bacteremic pneumonia and 38.0% in PPE) and children of >36 months (51.4% for 36 to 59 months and 40.0% for >59 months), while serotype 19A was linked to nonrespiratory IPDs (31.1% in meningitis, 27.3% in primary bacteremia, and 51.9% in others) and children of <24 months (35.9% for children of <12 months and 36.5% for those 12 to 23 months old), with high nonsusceptibility rates for penicillin, cefotaxime, and erythromycin. After PCV7 implementation, non-PCV7 serotypes caused 95.5% of IPDs. The new 13-valent conjugate vaccine would provide 79.1% coverage of serotypes responsible for IPDs in this series

Aperture effects on the oxygen abundance determinations from CALIFA data

This paper aims at providing aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA) database. In particular, we explore the behavior of the log([OIII]5007/Hbeta)/([NII]6583/Halpha) (O3N2) and log[NII]6583/Halpha (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star forming galaxies. We compute median growth curves of Halpha, Halpha/Hbeta, O3N2 and N2 up to 2.5R_50 and 1.5 disk R_eff. The growth curves simulate the effect of observing galaxies through apertures of varying radii. The median growth curve of the Halpha/Hbeta ratio monotonically decreases from the center towards larger radii, showing for small apertures a maximum value of ~10% larger than the integrated one. The median growth curve of N2 shows a similar behavior, decreasing from the center towards larger radii. No strong dependence is seen with the inclination, morphological type and stellar mass for these growth curves. Finally, the median growth curve of O3N2 increases monotonically with radius. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02<=z<=0.3 shows that the average difference between fiber-based and aperture corrected oxygen abundances, for different galaxy stellar mass and redshift ranges, reaches typically to ~11%, depending on the abundance calibration used. This average difference is found to be systematically biased, though still within the typical uncertainties of oxygen abundances derived from empirical calibrations. Caution must be exercised when using observations of galaxies for small radii (e.g. below 0.5R_eff) given the high dispersion shown around the median growth curves.Comment: Accepted for publication in Ap