Search Results

You are looking at 1 - 10 of 29 items for

  • Author or Editor: D. López x
  • Refine by Access: All Content x
Clear All Modify Search

We are immersed in a knowledge society that calls for indicators to go beyond economic factors to measure the development of a country. In this paper we use an adapted microeconomic model that determines the value of a country’s intellectual capital. For this, we consider intangibles such as human development, economic structure, international trade, foreign image and innovation. This measurement of intellectual capital is divided into human and structural capital and is used to analyse the relationship between these capitals and the economic development of the 27 countries in the European Union (EU27). The results show that when we consider aspects other than economic variables, the differences between countries are larger. Moreover, there is an inverse relationship between the management of intangibles and economic growth, which is why the former progresses after the latter have occurred.

Restricted access

Abstract  

A study was carried out in Havana City using lichen as monitor of air pollution. The concentration of several trace elements (Ca, Mn, Fe, Ni, Cu, Zn, Sr, Cd, Pb) in a total of 225 samples was determined by Total Reflection X Ray Fluorescence (TRXRF), Flame Atomic Absorption Spectroscopy (FAAS) and Anodic Stripping Voltammetry (ASV). In addition several Biological Certified Reference Materials (CRM’s) were analyzed in order to assess the analytical performance of the results. In general a relatively good agreement was found among the techniques. No significant differences were found between the obtained results and the certified reference values.

Restricted access

Background and aims

The Problem Gambling Severity Index (PGSI) is one of the most widely used screening tools for problem gambling (PG). However, to date, no empirically validated adaptation of the instrument to Spanish-speaking countries exists.

Methods

A sample of 659 sports bettors (M age = 35.1 years, SD = 10.12, 74.2% males) were recruited through an online research panel. A confirmatory factor analysis (CFA) was performed to confirm its construct validity. The participants were administered the Spanish version of the PGSI, along with the adaptation to Spanish of the DSM-IV PG instrument for convergent validity.

Results

The CFA of the Spanish PGSI showed satisfactory construct validity. The internal consistency (αordinal = .97) as well as its convergent validity with the DSM-IV scores (r = .77, p < .001) was good.

Conclusion

The Spanish adaptation of the PGSI offers satisfactory validity and reliability properties, and is a good psychometric instrument for exploring the social consequences of PG in Spanish-speaking contexts.

Open access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
R. López-Valenzuela
,
J. López-Palacios
,
M. Jiménez-Reyes
,
G. Cataño
, and
D. Tenorio

Abstract  

Thirteen Teotihuacan-style ornaments of an incense burner were studied. Ceramic pastes, pigments and mica were analyzed by neutron activation, X-ray diffraction and scanning electron microscopy. Elemental (Sc, Cr, Fe, Co, Rb, Cs, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Th and U) and statistical analyses of ceramic-body data showed that these pieces were made from the same raw material, which is chemically different from the fine orange ceramic of Teotihuacan. Montmorillonite and the classical components of sand were the minerals identified in the ceramic pastes. The white pigment contained calcium, titanium and aluminium, the yellow pigment was ocher, and the red pigment was a mixture of red ocher and cinnabar, the binder of the pigments being clay. Exoskeletons of diatoms and locust ootecs were found in the pigments. Mica was identified as biotite, identical with that coming from Monte Alban Oaxaca. We wish to undertake a historical reconstrution of these ornaments based on archaeometric and literature data.

Restricted access

Abstract  

Several ornaments named tezcacuitlapilli (coccyx-mirrors) are described and chemical analyses of raw materials (slate and pigments) were carried out by neutron activation, X-ray diffraction, scanning electron microscopy and radiography. Elemental and statistical analyses revealed that three different kinds of slate were used in their manufacture. The white pigment contains gypsum while ochre, yellow and red pigments contain iron oxide. These ornaments were identified as coming from the Cave of the Sun Pyramid of Teotihuacan. An attempt was undertaken to reconstruct the contexts of their manufacture and symbolic interpretation.

Restricted access

Summary The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.

Restricted access

Abstract  

Heat capacity measurements between 293 K and 363 K have been carried out in order to elucidate the different states appearing in 2-amino-2-methyl-1,3 propanediol (AMP) plastic crystal. The results allowed one of them to be identified as a glassy crystal. The changes of enthalpy, entropy and Gibbs free energy thermodynamic functions with temperature have been calculated from the experimental heat capacity values.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
O. Díaz Rizo
,
M. Manso Guevara
,
E. Herrera Peraza
,
I. Alvarez Pellón
,
M. López Reyes
,
D. López Aldana
, and
F. Garcia Yip

Abstract  

The experimental dependence of the α,f andT n parameters, in function of the water thickness, for different irradiation channels of Triga Mark III reactor, were analyzed. An exponential law for the α(r) dependence was obtained in the neighborhood of the active zone of the reactor numerically modelated using theS n method for 69 neutrons groups, and this dependence is slower in light water reactors than in graphite reactors.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
P. Lam Ramos
,
D. Frías Fonseca
,
M. González Garcia
,
D. Aguiar Lambert
,
J. Estévez Alvarez
,
I. Pupo González
, and
D. López Sánchez

Abstract  

The objective of the present study was the elaboration of a procedure for the determination of Y, La, Ce, Pr and Nd in soils by spectrophotometry with Arsenazo III preceded by a separation-concentration stage, which includes coprecipitation and ion exchange. Multielement analysis by energy dispersive X-ray fluorescence (including Y, La, Ce and Nd) and flame atomic absorption spectrophotometry was carried out simultaneously in order to obtain a general characterization of the soil samples. Certified reference materials and statistical intercomparison of the obtained results were used to evaluate the accuracy of the methods. The precision was examined by analyzing replicate samples.

Restricted access

Calorimetric measurements of the heat of adsorption of CO2 on zeolites with variable content of mono- and divalent cations lead to common conclusions. High initial heats (up to 120 kJ·mol−1 for NaA), generally associated with a slow and activated rate of adsorption, are found for high contents of Na+, Li+ or Ca2+. They are attributed to a limited number of chemisorption sites (0.3 per α cage in NaA).

Restricted access