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.     

Hyperfine structure in 5s 4d 3 D —5snf transitions of87Sr

The hyperfine spectra of the 5s4d ³ D ₁-5s20f, 5s4d ³ D ₂-5s23f, and 5s 4d ³ D ₃-5s32f transitions of⁸⁷Sr (I=9/2) have been measured by collinear fast beam laser spectroscopy. The structure in the upper configurations is highly perturbed by fine structure splitting that is of comparable size to the hyperfine interaction energy. These perturbations can be adequately treated with conventional matrix diagonalization methods, using the 5s-electron magnetic dipole interaction terma _5s and the unperturbed fine structure splittings as input parameters. Additionally, hyperfine constants for the lower 5s4d ³ D configurations, including theA- andB-factors and a separation of the individuals- andd-electron contributions to these factors, are derived.     

Characterization of the Reaction of Chloroacetaldehyde with Single and Double Stranded DNA

Chloroacetaldehyde reacts with viral M13mp18 single and double stranded DNA to form the highly fluorescent adducts, etheno-AMP and etheno-CMP.

Absorbance and fluorescence spectroscopy can be used to monitor and characterize these reactions. Both single and double stranded DNA showed increases in the absorbance following reaction with the aldehyde. The fluorescence also increased in these two groups and continued to rise with increasing time of incubation until a point of saturation was reached. The fluorescence of the double stranded moiety was considerably enhanced following reaction with the aldehyde while that of the single stranded population was not, making this method appropriate for the separation of small quantities of the two populations of DNA.     

Application of the single comparator method to instrumental photon activation analysis

Journal of Radioanalytical and Nuclear Chemistry - Instrumental photon activation analysis (IPAA) is nondestructive and multi-elemental analysis method like instrumental neutron activation...     

Twist-Bend Nematic Glasses: The Synthesis and Characterisation of Pyrene-based Nonsymmetric Dimers

A selection of pyrene-based liquid crystal dimers have been prepared, containing either methylene-ether or diether linked spacers of varying length and parity. All the diether linked materials, CBOnO.Py (n=5, 6, 11, 12), exhibit conventional nematic and smectic A phases, with the exception of CBO11O.Py which is exclusively nematic. The methylene-ether linked dimer, CBnO.Py, with an even-membered spacer (n=5) was solely nematogenic, but odd-members (n=6, 8, 10) exhibited both nematic and twist-bend nematic phases. Replacement of the cyanobiphenyl fragment by cyanoterphenyl giving CT6O.Py, gave elevated melting and nematic-isotropic transition temperatures, and SmA and SmC_A phases were observed on cooling the nematic phase. Intermolecular face-to-face associations of the pyrene moieties drive glass formation, and all these materials have a glass transition temperature at or above room temperature. The stability of the glassy twist-bend nematic phase allowed for its study using AFM, and the helical pitch length, P_TB, was measured as 6.3 and 6.7 nm for CB6O.Py and CB8O.Py, respectively. These values are comparable to the shortest pitch of a twist-bend nematic phase measured to date.     

Fast, low-level detection of strontium-90 and strontium-89 in environmental samples by collinear resonance ionization spectroscopy

Environmental assessment in the wake of a nuclear accident requires the rapid determination of the radiotoxic isotopes ⁸⁹Sr and ⁹⁰Sr. Useful measurements must be able to detect 10⁸ atoms in the presence of about 10¹⁸ atoms of the stable, naturally occurring isotopes. This paper describes a new approach to this problem using resonance ionization spectroscopy in collinear geometry, combined with classical mass separation. After collection and chemical separation, the strontium from a sample is surface-ionized and the ions are accelerated to an energy of about 30 keV. Initially, a magnetic mass separator provides an isotopic selectivity of about 10⁶. The ions are then neutralized by charge exchange and the resulting fast strontium atoms are selectively excited into high-lying atomic Rydberg states by narrow-band cw laser light in collinear geometry. The Rydberg atoms are then field-ionized and detected. Thus far, a total isotopic selectivity of S > 10¹⁰ and an overall efficiency of ξ = 5 × 10⁻⁶ have been achieved. The desired detection limit of 10⁸ atoms ⁹⁰Sr has been demonstrated with synthetic samples.     

Fast causal information transmission in a medium with a slow group velocity

It is widely believed that the velocity of information upsiloni encoded on an optical pulse is equal to the group velocity upsilong, at least when upsilong is less than the speed of light in vacuum c. On the other hand, several authors suggest that upsiloni=c, although the size of the signal traveling at this velocity may be small, thereby making it difficult to measure. Here, we measure upsiloni for pulses propagating through a resonant "slow-light" medium where upsilong approximately 0.006c. We find upsiloni=1.03c(+0.49c)-0.25c, or that upsiloni approximately 168upsilong, clearly demonstrating that the speed of information cannot be generally described by upsilong, but is characterized by its own velocity.