Application of FT-Raman spectroscopy to quality control in brick clays firing process.

This paper reports the study of the mineralogical evolution during the firing process (800-1150 degrees C) of the main types of raw materials used for the brick industry in Santa Cruz de Mudela (Ciudad Real, Spain). The mineralogical diversity observed in these materials leads to different behaviour during the shaping, drying and firing stages. Traditional use of similar working conditions in local industries, despite the mineralogical differences in the starting material, promotes the presence of defects in the drying and/or firing stages. This study attempt to implement some analytical guideline for the raw materials in order to improve the final product. Three types of raw materials obtained in different quarries have been characterised by means of chemical analysis with electron microprobe, powder X-ray diffraction and FT-Raman spectroscopy. The main difference between the clays studied is the carbonate content: one of the analysed samples is deficient in this component, while it is present as calcite (8%) or as calcite (14%) plus dolomite (10%) in the rest. The observed compositional differences seem to be relevant in the firing process. FT-Raman spectra reveal the onset of early vitrification (at about 900 degrees C) in the sample without carbonate. The importance of calcium and magnesium oxides, obtained from the corresponding carbonates, for the synthesis of new mineral phases that could slow down the vitrification process is discussed.

FT-Raman and powder XRD analysis of the Ba(SO(4))(x)(CrO(4))(1-x) solid solution.

The Ba(SO(4))(x)(CrO(4))(1-x) solid solution has been described in nature, forming the mineral Hashemite. From the geochemical point of view, however, anionic solid solutions have much interest because they are suitable systems to probe order-disorder phenomena. The solid solution analysed in the present study has, moreover, a special incentive in its possible use for the extraction from water, and immobilisation, of the pollutant Cr(VI) ion. The orthorhombic (space group Pnma) unit cell parameters of the solid solution change linearly with the mole fraction of both anions, decreasing with increase in the sulfate anion concentration. The vibrational spectroscopic study is centred on the behaviour of the anionic symmetric stretching band (nu(1),A(1)), whose characteristics are examined in detail. While the chromate anion band retains its wavenumber along the full compositional range, the sulfate anion band is shifted toward lower wavenumbers with decrease in the corresponding mole fraction. The positional disorder induced by the random anionic substitution results in strong increase of the halfwidth in both bands, which becomes greatest in the central member of the series.

Natural immunity to measles, rubella and mumps among Spanish children in the pre-vaccination era.

Prior to the start of mass vaccination campaigns against measles, rubella and mumps, a prevalence study of natural immunity to these diseases was undertaken in a sample of 1700 unvaccinated Spanish children. They were representative of the 3-7 year-old population in terms of age, regional distribution and urban or rural environment. Measles infection prevalence was significantly higher than that for rubella and mumps from 3 (48.3%, 14.2%, 25.5%, respectively) through 7 years of age, (64%, 40.9%, 39%). As a function of age, naturally-acquired immunity increased according to parabolic progressions. In the 3-5 year-old group, rural environment, low socioeconomic status, no school attendance and lack of brothers were associated with statistically lower levels of measles, rubella, or mumps infection. In the 6-7 year-old group, only 12% of the children showed antibodies against the three diseases and 18.7% exhibited triple susceptibility.