Performance effects on the voices of 10 choral tenors: Acoustic and perceptual findings

Trained choral tenors performed a series of vocal tasks before and after a “live” performance. Acoustic (perturbation, harmonic-to-noise ratio, pitch and amplitude ranges) and perceptual analyses (auditory and proprioceptive/kinesthetic) were undertaken to detect changes from pre- to postperformance. Individuality of response to the performance was revealed, with the majority of subjects showing vocal deterioration after performance. The most sensitive vocal tasks were the comfortably pitched notes, high soft notes, and the bottom notes in scale singing. The most sensitive acoustic measure in detecting change from pre- to postperformance was harmonic-to-noise ratio. In contrast to the demonstrated acoustic changes, no significant differences in perceptual ratings were evident after the performance. Perceptual ratings did not reflect the acoustic analysis results. The present study highlights the need to establish further normative data for the singing voice and to consider individual differences in vocal characteristics in future studies of the singing voice.     

Identification of a new isotope,168Dy

A previously unreported nuclide,¹⁶⁸Dy, has been identified and found to have a half-life of 8.5+-0.5 min. The activity was produced in the spontaneous fission of²⁵²Cf and transported via a He jet system to a rapid radiochemical separative facility where the Dy fraction was removed from the mixed fission products. The assignment of this activity to¹⁶⁸Dy decay was based on the presence of five γ rays in the chemically separated Dy fraction which were associated with the decay of an 8.5-min activity and on the observation of the grow-in and subsequent decay of the daughter, 2.98-min¹⁶⁸Ho, with approximately an 8-min half-life. The γ-ray emission probabilities have been determined.     

Calibration and use of the Chemcatcher passive sampler for monitoring organotin compounds in water

An integrative passive sampler (Chemcatcher^®) consisting of a 47 mm C₁₈ Empore™ disk as the receiving phase overlaid with a thin cellulose acetate diffusion membrane was developed and calibrated for the measurement of time-weighted average water concentrations of organotin compounds [monobutyltin (MBT), dibutyltin (DBT), tributlytin (TBT) and triphenyltin (TPhT)] in water. The effect of water temperature and turbulence on the uptake rate of these analytes was evaluated in the laboratory using a flow-through tank. Uptake was linear over a 14-day period being in the range: MBT (3-23 mL day⁻¹), DBT (40-200 mL day⁻¹), TBT (30-200 mL day⁻¹) and TPhT (30-190 mL day⁻¹) for all the different conditions tested. These sampling rates were high enough to permit the use of the Chemcatcher^® to monitor levels of organotin compounds typically found in polluted aquatic environments. Using gas chromatography (GC) with either ICP-MS or flame photometric detection, limits of detection for the device (14-day deployment) for the different organotin compounds in water were in the range of 0.2-7.5 ng L⁻¹, and once accumulated in the receiving phase the compounds were stable over prolonged periods. Due to anisotropic exchange kinetics, performance reference compounds could not be used with this passive sampling system to compensate for changes in sampling rate due to variations in water temperature, turbulence and biofouling of the surface of the diffusion membrane during field deployments. The performance of the Chemcatcher^® was evaluated alongside spot water sampling in Alicante Habour, Spain which is known to contain elevated levels of organotin compounds. The samplers provided time-weighted average concentrations of the bioavailable fractions of the tin compounds where environmental concentrations fluctuated markedly in time.     

Above threshold dissociation of vibrationally cold HD+ molecules

The experimental study of molecular dissociation of H2+ by intense laser pulses is complicated by the fact that the ions are initially produced in a wide range of vibrational states, each of which responds differently to the laser field. An electrostatic storage device has been used to radiatively cool HD+ ions enabling the observation of above threshold dissociation from the ground vibrational state by 40 fs laser pulses at 800 nm. At the highest intensities used, dissociation through the absorption of at least four photons is found to be the dominant process.     

Simulation of ultrasonic-driven gas separations

The separation of components in a gas mixture is important for a wide range of applications. One method for achieving this separation is by passing a traveling acoustic wave through the gas mixture, which creates a flux of the lighter components away from the transducer. A series of simulations was performed to assess the effectiveness of this method for separating a binary mixture of argon and helium using the lattice kinetics method. The energy transport equation was modified to account for adiabatic expansion and compression. The species transport equation was modified to include a barodiffusion term. Simulations were performed on two different scales; detailed acoustic wave simulations to determine the net component flux as a function of local concentration, pressure, etc. and device scale simulations to predict the gas composition as a function of time inside a gas separation cylinder. The method is first validated using data from literature and then applied to mixtures of argon and helium. Results are presented and discussed.     

LIAD-fs scheme for studies of ultrafast laser interactions with gas phase biomolecules

Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities >10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency.     

Properties of the self-consistent field treatment of conjugated molecules

The polarizability properties of π electron systems are treated by the self-consistent field method, as modified by Pople for application to conjugated molecules. An analytical treatment of the π electron configuration of substituted hydrocarbons deduces certain universal symmetry properties of this method, and contains the Hückel treatment of inductive substituents as a simplified special case. Whereas the usual Hückel theory derives results by approximate perturbation methods, the treatment given here is formally exact. In a later section s.c.f. polarizability coefficients, as calculated on an Elliott 402 digital computer, are given for benzene, naphthalene, anthracene and phenanthrene, and the predictions of chemical properties are shown to be in better agreement with experiment than predictions derived from Hückel theory.     

Self-reported voice problems among three groups of professional singers

A vocal health questionnaire was administered to three groups of professional singers and a “friendship-matched” group of nonsingers in Melbourne, Australia. The responses of 79 opera, 57 musical theatre and 31 contemporary (excluding rock) singers and 86 nonsingers were analysed. The questionnaire solicited information regarding biographical data speaking and singing voice-use behaviours, and vocal health over the previous 12 months in terms of experiences of vocal impairment, vocal disability, and handicap. Significant differences between singers and nonsingers in the prevalence and nature of voice problems were reported. Of the singers, 44% reported one or more occurrences of a diagnosed vocal condition compared to 21% of nonsingers and 69% of singers experienced vocal disability compared to only 41% of nonsingers, over the previous 12 months. In contrast, no significant differences were found between the three different styles of singers in their experience of vocal impairment, disability or handicap.     

Dearomatization of Electron‐Deficient Phenols to ortho‐Quinones: Bidentate Nitrogen‐Ligated Iodine(V) Reagents

Despite their broad utility, the synthesis of ortho‐quinones remains a significant challenge, in particular, access to electron‐deficient derivatives remains an unsolved problem. Reported here is the first general method for the synthesis of electron‐deficient ortho‐quinones by direct oxidation of phenols. The reaction is enabled by a novel bidentate nitrogen‐ligated iodine(V) reagent, a previously unexplored class of compounds which we have termed Bi(N)‐HVIs. The reaction is extremely general and proceeds with excellent regioselectivity for the ortho over para isomer. Functionalization of the ortho‐quinone products was examined, resulting in a facile one‐pot synthesis of catechols, as well as the incorporation of a variety of heteroatom nucleophiles. This method represents the first synthetic application of Bi(N)‐HVIs and demonstrates their potential as a platform for the further development of highly reactive, but also highly tunable, I(V) reagents.