In this work the self-organized mesophases obtained by the ionic interaction of poly(amino acids)
poly(l-aspartic acid (P-l-Asp) and poly(l-glutamic acid) (P-l-Glu) with the cationic surfactants C14TAB
and C16TAB, as well as the mesoporous silicate materials obtained by addition and hydrolysis of tetraethyl
orthosilicate (TEOS) on the hybridic mesophases, are described. The mesophases isolated at pH 6.5−8.5
were examined by X-ray diffraction (XRD) analysis for their structure, thermogravimetry for their thermal
stability, scanning electron microscopy for their structural features, and circular dichroism (CD) for the
conformation of the polypeptide−C
n
TAB (n = 14, 16) complexes. The mesophases P-l-Asp/C14TAB
isolated at pH 7.5 and 8.5 showed in XRD a single peak at d = 3.45 nm and d = 3.54 nm, respectively,
corresponding to typical hexagonal packing of the micellar aggregates. The mesophases P-l-Asp/C16TAB isolated at pH 7.5 showed an XRD peak at d = 3.90 nm, corresponding to a similar hexagonal
packing of larger micellar aggregates and also two peaks at d = 3.37 nm and d = 1.69 nm indicating a
layered configuration of the micellar sheets. The layered component decreases by the increase of pH
from 7.5 to 8.5 or the addition of small amounts (0.5%) of EtOH. The P-l-Glu/C14TAB mesophases
isolated at pH 7.5 and 8.5 showed a single XRD peak at d = 3.60 nm, while the P-l-Glu/C16TAB system
showed also a single XRD peak at d = 4.10 nm. The CD spectra showed that the complexes P-l-Asp/C14TAB possess a more random configuration compared to the P-l-Glu/C14TAB, which have the tendency
to form α- and 310-helices. The mesoporous silicate materials obtained from the systems P-l-Asp/C16TAB/TEOS and P-l-Glu/C16TAB/TEOS showed a single XRD peak corresponding to hexagonal pore
arrangement typical in MCM-41 materials. The nitrogen adsorption−desorption isotherms of the silicate
mesostructures indicate that they possess high surface areas in the range 500−800 m2 g-1 for the P-l-Asp/C
n
TAB/TEOS and 1000−1070 m2 g-1 for the P-l-Glu/C
n
TAB/TEOS and ordered or semi-ordered
porosity depending on the hybridic system used for isolating the corresponding mesophases.
Objective is to evaluate the impact of occupational exposure to lignite dust on respiratory system. 103 blue-collar workers exposed to lignite dust and 62 controls completed a questionnaire on respiratory symptoms and underwent spirometry. Levels of lignite dust in workplace were measured. Univariate and multivariate analysis of the data were performed. The concentration of lignite dust varied from 0.6 to 1.4 mg/m 3 . Current smokers and workers exposed to lignite dust presented higher prevalence of chronic bronchitis symptoms and of FEV<80% and FEV1/FVC<70%. Multivariate analysis has shown that smoking and occupational exposure to lignite dust were independent predictors of chronic bronchitis symptoms, as well as of an obstructive ventilation pattern. Further analysis showed that exposed workers who were current smokers presented a five fold rate for developing an obstructive ventilation pattern in comparison to exposed workers non currently smokers. Occupational exposure to lignite dust and smoking were independent determinants of chronic bronchitis symptoms and obstructive ventilation pattern. There is some evidence for a combined effect of smoking and lignite dust exposure on respiratory system.
SIM.QM-S7 was performed to assess the analytical capabilities of National Metrology Institutes (NMIs) and Designated Institutes (DIs) of SIM members (or other regions) for the accurate determination of trace metals in drinking water. The study was proposed by the coordinating laboratories National Research Council Canada (NRC) and Centro Nacional de Metrologia (CENAM) as an activity of Inorganic Analysis Working Group (IAWG) of Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM). Participants included 16 NMIs/DIs from 15 countries. No measurement method was prescribed by the coordinating laboratories. Therefore, NMIs used measurement methods of their choice. However, the majority of NMIs/DIs used ICP-MS.
This SIM.QM-S7 Supplementary Comparison provides NMIs/DIs with the needed evidence for CMC claims for trace elements in fresh waters and similar matrices.
Main text
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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