A Raman study of the pressure-induced densification of SiO2-based glass-ceramics.

Here we report a structural characterization study of glass-ceramics as a function of pressure by Raman spectroscopy. We selected a glass-ceramics of Li2O-Al2O3-nSiO2 (n ≈ 8) doped with ZrO2 and TiO2. This composition induces slight structural modification in Si-O and Si-O-Si bonds in the glass matrix that are crucial to stabilize metastable hexagonal SiO2 (ß-quartz) solid-solution nano crystals corresponding to γ-LiAlSi2O6. This structure yields a more compact ß-quartz-type phase that eventually stabilizes it in wider pressure range than pure SiO2. Raman spectroscopy allows to unravel at least two pressure-induced structural phase transitions at about 6 and 15 GPa that could not be previously revealed by x-ray diffraction. We show that the phase-transition sequence can tentatively be described in terms of SiO2-type structure as: ß-quartz → Coesite I → Coesite II. The measured transition pressures are consistent with the larger cell volume attained in the γ-LiAlSi2O6 yielding a wider metastability pressure range of the ß-quartz-type phase.

[Inflammation and infection in stable coronary disease and acute coronary syndrome]. / Inflamación e infección en la enfermedad coronaria estable y en el síndrome coronario agudo.

OBJECTIVE: To study whether inflammation and infection are related to coronary artery disease. DESIGN: Sixty patients (44 males, mean age 62 +/- 13 years) with acute coronary syndrome and 40 with stable coronary artery disease (31 males, age 64 +/- 10 years) and a control group of 40 individuals (34 males, 53 +/- 5 years) were analyzed. IgG against Chlamydia pneumoniae, Cytomegalovirus and Helicobacter pylori plus C-reactive protein were assessed in all serum samples. In addition, IgM against C. pneumoniae and Cytomegalovirus on admission and C-reactive protein one month later were measured in acute patients. RESULTS: No IgM seropositivity was observed. A high prevalence of IgG seropositivity with no significant differences among the groups was found: C. pneumoniae: acute group 44 (73%), stable group 29 (73%) and control group 25 (63%); Cytomegalovirus: 55 (92%), 37 (92%) and 38 (95%), respectively; and H. pylori, 43 (72%), 32 (80%) and 34 (85%) respectively. There was a high rate of positive C-reactive protein in the acute group: 48 (80%) vs 10 (25%) the stable group and 0% the control group (p < 0.001). C-reactive protein levels were higher in Q-wave infarction than in unstable angina/ non-Q-wave infarction (median 22.65 vs 7.69, p < 0.001). One month later, C-reactive protein levels decreased (median 22.65 vs 3.38, p < 0.001), but were still positive in 40%. CONCLUSIONS: These data suggest that inflammation is detected by the commonly used methods in clinic practice in acute coronary syndromes and to a lesser extent in stable coronary artery disease. It seems that different mechanisms other than infection account for this inflammatory response, at least this being so when infection is assessed by serology. Serology does not appear to be an adequate method to determine the possible relationship among coronary syndromes, infection and inflammation.

Importancia nutricional de la miel: un edulcorante natural / Nutritional importance of honey: a natural sweetener

En este trabajo se muestra la composición porcentual media de la miel, tanto en macro como en micronutrientes, y se establece una comparación con el azúcar común. Además se presenta el porcentaje con el que la miel contribuye a cubrir las cantidades diarias recomendadas (CDR) de los distintos nutrientes que contiene, considerando una ingesta diaria de 50 gramos de este alimento, para hombres y mujeres pertenecientes a tres grupos de edades diferentes: 19-24, 25-50 y mayores de 50 (AU)