A Pilot Survey of Vocal Health in Young Singers

The objective of this study was to determine the incidence of vocal problems in young choir singers and to correlate vocal problems with demographic and behavioral information. A questionnaire addressing vocal habits and hygiene was offered to 571 young choir singers, up to 25 years of age, who sing at least weekly; 129 (22.6%) responded. More than one-half of the respondents had experienced vocal difficulty, particularly older adolescents. Detrimental behaviors and circumstances surveyed were not reflective of the incidence of vocal difficulty, except for morning hoarseness, chronic fatigue, insomnia, and female gender after puberty. Voice care professionals should be aware that self-reported voice difficulties are common among young choral singers, especially postpubescent girls, and children with symptoms consistent with reflux (morning hoarseness) and emotional stress (insomnia). Laryngologists should communicate with choral conductors and singing teachers to enhance early identification and treatment of children with voice complaints, and to develop choral educational strategies that help decrease their incidence.     

Materials for spintronic: Room temperature ferromagnetism in Zn–Mn–O interfaces

In this paper we study the room temperature ferromagnetism reported on Mn-doped ZnO and ascribed to spin polarization of conduction electrons. We experimentally show that the ferromagnetic behaviour is associated to the coexistence of Mn³⁺ and Mn⁺⁴ in MnO₂ grains where diffusion of Zn promotes the Mn⁴⁺→Mn³⁺ reduction. Potential uses of this material in spintronic devices are analysed.     

Complex transformations of the curvature tensor

It is shown that complex transformations can be applied on the parameters and coordinates entering a known curvature tensor in order to generate new curvature tensors which, just as the seed tensor, possess the same symmetry properties and satisfy certain algebraic relationships following from the Einstein-Maxwell equations with cosmological constant.     

Magneto-volume effects in Fe–Cu solid solutions

The magnetic properties of Fe–Cu metastable solid solutions have been investigated by means of neutron diffraction and magnetisation measurements. These compounds exhibit ferromagnetic order with Curie temperatures above room temperature for concentrations beyond 40 at% in Fe. The magnetic moment at 5 K can reach values over 2 μ_B, while the high field susceptibility is similar to that found in FCC–FeNi Invar alloys. These features together with the low values for the linear coefficient for thermal expansion in the ferromagnetic region suggest that magneto-volume anomalies, including Invar behaviour, play a major role in the magnetic properties of this system when the crystal structure is face centred cubic. Such behaviour could be explained using theoretical total-band energy calculations.     

Toxicity assays applied to wastewater treatment

The utility and validity of toxicity tests for monitoring of wastewater treatment have been assessed. The evaluated acute toxicity tests have been Vibrio fischeri, Selenastrum capricornotum and Daphnia magna tests. The validation studies indicated that the acute toxicity tests can be considered as high sensitivity analytical tools to detect common environmental concentrations of the pollutants at concentration levels as low as ng l⁻¹. The toxicity tests showed to have discriminatory ability to distinguish between different degrees of toxicity, and the toxic specificity of the compounds on target organisms. Synergistic, additive or antagonistic effects were evaluated indicating the capacity of the toxicity test to assess the combined effects of chemicals in wastewaters. The reproducibility of these tests, calculated as relative standard deviation, is acceptable in the range of 5-22.3%. The application of multivariate date analysis proved that toxicity and chemical measures are complementary analytical tools for monitoring of wastewaters quality. The toxicity tests are useful analytical tools for screening of chemical analysis and as an early warning system to monitor the treatment of WWTPs. The use of single toxicity test or battery of tests is the best approach to evaluate the risk because they are reliable indices of the toxic impact of effluents in the aquatic environment. The toxicity tests were applied in the quality control of different European WWTPs.     

Microwave-assisted solid-phase synthesis of peptoids

Microwave irradiation reduces the reaction time for the solid-phase synthesis of peptoids. Under these conditions, coupling of each residue requires only 1 min. The purity and yields of peptoids synthesized in this way are as good as or better than those achieved using standard methods. [reaction: see text]     

The correlation of the stability constants of 1,3-dicarbonylic monochelates of Iron(III) with the acid dissociation constants of the ligand

The variation of the logrithms of stability constants of iron(III) monochelated compounds with structurally similar 1,3-dicarbonylic compounds has been found to be an essentially linear function of the negative logarithms of the acid ionization constant of the ligands. An analytical correlation which could be useful to predict equilibrium constants of iron(III) chelates has been developed. From spectrophotometric and potentiometric data a quantitative evaluation of the stability of the complex has been carried out. Results have provided information regarding substituent effects on the equilibrium constants.     

Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser

A selective and sensitive chromatographic method is described for the determination of nine organochlorine and organophosphorus pesticides in vegetable samples by gas chromatography-mass spectrometry. The proposed method combines the use of positive and negative chemical ionisation and tandem mass spectrometric fragmentation, resulting in a significant increase in selectivity and allowing the simultaneous confirmation and quantification of trace levels of pesticides in complex vegetable matrices. Parameters relative to ionisation and fragmentation processes were optimised to obtain maximum sensitivity. Repeatability and reproducibility studies yielded relative standard deviations lower than 25% in all cases. Identification criteria, such as retention time and relative abundance of characteristic product ions, were also evaluated in order to guarantee the correct identification of the target compounds. The method was applied to real vegetable samples to demonstrate its use in routine analysis.