Noise exposure of workers of the construction sector

Noise is one of the most highly found physical contaminants in the construction sector. The most negative effects caused by noise exposure are related to the hearing system and may produce professional deafness or even permanent deafness. As these effects have a very important influence on people’s health and well-being, it is necessary to assess the noise exposure and to develop mechanisms for studying and proposing preventive solutions.This work has studied the noise levels which the workers of the construction sector are exposed to. A number of representative measurements have been carried out using a sound level meter and a dosimeter to collect data from workers devoted to different tasks in the construction process. Analysis of the most important levels and indexes have been done with those data, and afterwards, they have been compared with the limits imposed by the different current regulations.     

Experimental densities,refractive indices,and speeds of sound of 12 binary mixtures containing alkanes and aromatic compounds at T = 313.15 K

Densities, speeds of sound, and refractive indices of 12 binary systems of alkanes (hexane, heptane, octane, and nonane) with aromatics (benzene, or toluene, or ethylbenzene) at T = 313.15 K and at atmospheric pressure were determined over the whole composition range, and are presented in this paper. From the experimental results, the derived and excess properties (isentropic compressibility, excess molar volumes, and excess molar isentropic compressibility) at T = 313.15 K were calculated and satisfactorily fitted to the Redlich–Kister equation.     

Self-assembly of a tetranuclear Ni4 cluster with an S = 4 ground state: the first 3d metal cluster bearing a mu4-eta2:eta2-O,O carbonate ligand

Reaction of nickel(II) acetate with H(3)L (2-(5-bromo-2-hydroxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) yields [Ni(2)L(OAc)(H(2)O)(2)].3MeCN.2H(2)O (1.3MeCN.2H(2)O), crystallographically characterized. 1 is unstable in solution for a long time and hydrolyzes to give [Ni(2)L(o-OC(6)H(3)BrCHO)(H(2)O)].2.25MeCN.H(2)O (2.2.25MeCN.H(2)O). In addition, 1 uptakes CO(2) from air in a basic methanol/acetonitrile solution, yielding [[Ni(2)L(MeOH)](2)(CO(3))].1.5MeOH.MeCN.H(2)O (3.1.5MeOH.MeCN.H(2)O). The X-ray characterization of 3 reveals that it is a tetranuclear nickel cluster, which can be considered as the result of a self-assembly process from two dinuclear [Ni(2)L](+) blocks, joined by a mu(4)-eta(2):eta(2)-O,O carbonate ligand. The coordination mode of the carbonate anion is highly unusual and, to the best of our knowledge, it has not been described thus far for first-row transition metal complexes or magnetically studied until now. Magnetic characterization of 1 and 3 shows net intramolecular ferromagnetic coupling between the metal atoms in both cases, with S = 2 and S = 4 ground states for 1 and 3, respectively.     

Antioxidant-substituted tetrapyrazinoporphyrazine as a fluorescent sensor for basic anions

Tetrapyrazinoporphyrazine substituted at its periphery with eight antioxidant 3,5-di-t-butyl-4-hydroxyphenyl groups behaves as a turn-on fluorescent sensor for fluoride anions. Conversely, the precursor antioxidant-substituted 1,2-phthalonitrile was found to act in turn-off mode suggesting that the origin of the phenomenon lies at the phenolate-substituted 1,4-pyrazinyl moiety.     

Chiral Determination of Salbutamol, Salmeterol and Atenolol by Two-Dimensional LC–LC: Application to Urine Samples

A heart-cut two-dimensional high-performance liquid chromatography method for enantiomeric determination of salbutamol, salmeterol and atenolol in urine is presented. It involves the use of two separations in a liquid chromatography?Cliquid chromatography achiral?Cchiral coupling. Target compounds were previously separated in a primary column (Kinetex? HILIC, 2.6???m, 150?×?2.1?mm I.D.) with a mixture of MeOH:ACN:ammonium acetate buffer (5?mM, pH 6) 90:5:5 (v/v/v) as mobile phase at a flow rate of 0.40?mL?min^?1. Enantiomeric separation was carried out by transferring peak of each compound through a switching valve to a vancomycin chiral column (Chirobiotic? V, 2.6???m, 150?×?2.1?mm I.D.) using MeOH:ammonium acetate buffer (2?mM, pH 4) 97:3 (v/v) as mobile phase at a flow rate of 0.50?mL?min^?1. Ultraviolet detection was done at 227?nm. The method was applied to determine target analytes in urine samples after enzymatic hydrolysis with ??-glucuronidase from Helix pomatia, followed by a solid-phase extraction procedure using Isolute^? HCX mixed-mode cartridges. Extraction recoveries ranged from 82 to 90?% in urine samples. Detection limits were 0.091?C0.095???g for each enantiomer of atenolol and between 0.058 and 0.076 and 0.18?C0.14???g for enantiomers of salbutamol and salmeterol, respectively (3?mL of urine). Linearity ranges were between 0.5 and 10???g?mL^?1. Intraday and interday reproducibilities of enantiomeric ratio and enantiomeric fraction, expressed as relative standard deviation, were between 1.9 and 9.0?%. The optimized method was successfully applied to the analysis of urine samples obtained from excretion studies in volunteers and in freeze-dried urine samples, containing urinary components with MW?<?10,000 and components with MW?>?10,000, spiked with different amounts of studied drugs.     

An extension of the grid empowered molecular simulator to quantum reactive scattering

Within the activities of the D37 COST Action, we have further developed the quantum dynamics framework of the grid empowered molecular simulator (GEMS) implemented on the segment of the European grid available to the COMPCHEM (computational chemistry) virtual organization. GEMS does now include in a full ab initio approach, the evaluation of the detailed quantum (both time dependent and time independent) dynamics of small systems starting from the calculation of the electronic structure properties as well as the direct calculation of thermalized properties. Illustrative, full dimensional applications of the extended simulator to the H + H(2) , N + N(2) , and O + O(2) systems are presented.     

New Promises and Opportunities in 3D Printable Inks Based on Coordination Compounds for the Creation of Objects with Multiple Applications

This review focuses on the usefulness of coordination bonds to create 3D printable inks and shows how the union of chemistry and 3D technology contributes to new scientific advances, by allowing amorphous or polycrystalline solids to be transformed into objects with the desired shape for successful applications. The review clearly shows how there has been considerable increase in the manufacture of objects based on the combination of organic matrices and coordination compounds. These coordination compounds are usually homogeneously dispersed within the matrix, anchored onto a proper support or coating the printed object, without destroying their unique properties. Advances are so rapid that today it is already possible to 3D print objects made exclusively from coordination compounds without additives. The new printable inks are made mainly with nanoscale nonporous coordination polymers, metal–organic gels, or metal–organic frameworks. The highly dynamic coordination bond allows the creation of objects, which respond to stimuli, that can act as sensors and be used for drug delivery. In addition, the combination of metal–organic frameworks with 3D printing allows the adsorption or selective capacity of the object to be increased, relative to that of the original compound, which is useful in energy storage, gas separation, or water pollutant elimination. Furthermore, the presence of the metal ion can give them new properties, such as luminescence, that are useful for application in sensors or anticounterfeiting. Technological advances, the combination of various printing techniques, and the properties of coordination bonds lead to the creation of surprising, new, printable inks and objects with highly complex shapes that will close the gap between academia and industry for research into coordination compounds.     

XPS study of the surface properties and Ni particle size determination of Ni‐supported catalysts

The surface properties of Ni/MgAl₂O₄ catalysts doped with Ce or Pr were analyzed by XPS after treatment in an inert and reductive atmosphere at 400 °C. The Ce‐promoted solids presented the Ce³⁺/Ce⁴⁺ couple on the surface even after treatment in a reductive atmosphere, H₂(5%)/Ar. The promotion effect of Ce on these solids could be associated with their participation on the carbon deposition‐removal mechanism. Pr‐doped catalysts showed a very high concentration of Pr³⁺ under a reductive atmosphere and the redox behavior associated with the carbon removal could be partially inhibited or become slower. The size of the Ni⁰ particles after both an inert and a reductive atmosphere was estimated by XPS intensity ratio using the model proposed by Davis. The results obtained from the Davis model showed that an important increase occurred in Ni particle size after treatment in H₂(5%)/Ar for the Pr‐promoted solids. The metal sintering under reductive atmosphere could be the reason for the higher loss of activity of the Pr‐doped solids under reforming conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of perfluorinated compounds in biota by microextraction with tetrahydrofuran and liquid chromatography/ion isolation-based ion-trap mass spectrometry

An analytical method combining both a simple, fast and efficient solvent microextraction and a sensitive and selective monitoring mode, based on ion isolation ion-trap mass spectrometry (MS), was developed for analysis of perfluorinated compounds (PFCs) in biota. The method involved the vortex-shaking of 0.2 g of tissue sample and 800 μL of tetrahydrofuran (THF):water (75:25, v/v) for 7 min, subsequent centrifugation for 13 min and direct quantitation of PFCs in the extract against solvent-based calibration curves. Selection of solvent composition was based on Hildebrand solubility parameters and their components (i.e. dispersion, dipole–dipole and hydrogen bonding forces). Recoveries in samples for PFCs with hydrocarbon chain lengths between C₄ and C₁₄ ranged from 85 to 111%, with relative standard deviations between 1 and 11%. The ion isolation monitoring mode, proposed for the first time for ion-trap-MS quantitation, proved to be effective in avoiding space-charge effects caused by co-eluting matrix components while keeping the sensitivity of full scan MS operation. Detection limits of the method were in the range 0.8−6 ng g⁻¹ for perfluoroalkyl carboxylates (PFACs) and 0.4–0.8 ng g⁻¹ for perfluoroalkyl sulfonates (PFASs) in wet weight samples. The method was validated using a reference material made up of flounder muscle and by comparison with triple quadrupole MS measurements and it was applied to the determination of PFCs in liver and muscle samples from sea birds and fishes. Only PFASs were found in samples at quantifiable levels (2.9 and 13.1 ng g⁻¹) while PFACs were below the respective quantitation limits. This method allows quick and simple microextraction of PFCs with minimal solvent consumption, while delivering accurate and precise data.