Prevalence of voice problems in teachers

Teachers are frequently cited as experiencing a high rate of vocal dysfunction (1–7). Despite considerable research in the area of voice problems in teachers, the prevalence of voice disorders in this group is unknown. This study investigated the prevalence of self-reported voice problems in teachers using a mail survey of a simple random sample of 1168 state school teachers (preschool-Grade 12) in South Australia. As part of the survey, teachers were asked to report voice problems for the day of the survey, during the current teaching year, and during their careers. The response rate was 75%, with 16% of teachers reporting voice problems on the day of the survey, 20% reporting problems during the current teaching year, and 19% reporting problems at some time during their career. Females were twice as likely as males to report voice problems. These findings clearly indicate a need for further investigation of the causes of vocal dysfunction in teachers and for the development of educational programs aimed at preventing voice problems in this group of professional voice users.     

Direct comparison of two cold-atom-based optical frequency standards by using a femtosecond-laser comb

With a fiber-broadened, femtosecond-laser frequency comb, the 76-THz interval between two laser-cooled optical frequency standards was measured with a statistical uncertainty of 2x10(-13) in 5 s , to our knowledge the best short-term instability thus far reported for an optical frequency measurement. One standard is based on the calcium intercombination line at 657 nm, and the other, on the mercury ion electric-quadrupole transition at 282 nm. By linking this measurement to the known Ca frequency, we report a new frequency value for the Hg(+) clock transition with an improvement in accuracy of ~10(5) compared with its best previous measurement.     

Excluded volume effects and fractional viscoelasticity in polymers

Meccanica - The excluded volume effect is added to a fractional viscoelastic model for modeling fractal polymers. This reveals a physical connection between the fractional time derivative, fractal...     

Vocal problems among teachers: a review of prevalence, causes, prevention, and treatment

Voice disorders are thought to be one of the major occupational hazardsof school teaching. The resulting symptoms can affect teachers' ability to function in the classroom and prevent them from developing effective working relationships with other staff and students. Sick leave, speech pathology management, and surgical intervention can be costly. Severe voice problems can also result in a teacher permanently leaving the classroom. Despite the significant implications of voice disorders for teachers, this review of published research demonstrates that findings concerning the prevalence of voice problems in teachers and the causes and contributing factors of those voice problems are inconclusive. Similarly, previous research on the efficacy of prevention programs and treatment of voice problems in teachers provide few firm conclusions. Further research based on sound empirical data is needed, as many past studies have relied on anecdotal or self-report data. More operational definitions of what constitutes a voice disorder and the associated contributing factors should be adopted, along with the use of more instrumental measures and careful attention to methodology and appropriate statistical analyses. Only then will we have a sound basis for the development of effective prevention and education programs for teachers.     

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.     

Iron-57 Mössbauer spectroscopic studies of the weathering of L-chondrite meteorites

Some L-chondrite meteorites found in the arid desert region of Roosevelt County in New Mexico, USA, and¹⁴C dated to determine the terrestrial age have been examined by⁵⁷Fe Mössbauer spectroscopy. The preliminary results reported here suggest that the initial weathering processes involve oxidation of iron in the iron-nickel alloy. After prolonged exposure to terrestrial weathering for approximately 36 000 years, the iron(II)-sulphide and -silicate phases are also oxidised. The corrosion products are complex and include paramagnetic Fe³⁺ species and macroscopic iron(III) oxide and/or oxyhydroxide phases. A meteorite which fell approximately 16 500 years ago at the end of the last glaciation showed extensive corrosion despite its relatively short terrestrial age. The result is associated with climatic changes which occurred at that time.     

Metal-insulator crossover in high T c cuprates: A gauge field approach

A metal-insulator crossover appears in the experimental data for in-plane resistivity of underdoped cuprates and a range of superconducting cuprates in the presence of a strong magnetic field suppressing superconductivity. We propose an explanation for this phenomenon based on a gauge field theory approach to the t-J model. In this approach, based on a formal spin-charge separation, the low energy effective action describes gapful spinons (with a theoretically derived doping dependence of the gap m _s ² ∼ δ| ln δ|) and holons with finite Fermi surface (ɛF ∼ tδ) interacting via a gauge field whose basic effect on the spinons is to bind them into overdamped spin waves, shifting their gap by a damping term linear in T, which causes the metal-insulator crossover. The presence of a magnetic field perpendicular to the plane acts by increasing the damping, in turn producing a big positive transverse in-plane magnetoresistance at low T, as experimentally observed.