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.     

Neutron activation and the JFK assassination, Part I. Data and interpretation

Five lead fragments from bullet cores from the assassination of American President John F. Kennedy in 1963 were analyzed twice by NAA, first by the FBI in 1964 and then by Vincent P. Guinn in 1977. Their concentrations of Sb have provided invaluable information about the number and origin of bullets that hit Kennedy and Texas Governor John B. Connally. While both analyses appeared to group the fragments into a body shot and a head shot, the FBI set contained a systematic error and Guinn's results from quarters of test bullets showed that the indicator element Sb varied enough over quarters to potentially merge the groups. The latter problem was resolved by the FBI replicate analyses, which showed that antimony was nearly homogeneos on the small scales of the fragments, and by the mechanism by which jacketed bullets break when hitting bone, which generates tiny fragments from a single break near the middle of the lead core. They collectively meant that the fragments within each group were formed on the scale of subfragments. The two groups were just as they appear because the larger quarter-bullet heterogeneities did not apply. This result substantiates Guinn's original conclusion that two and only two bullets from Lee Harvey Oswald's rifle struck the two men. This revised version was published online in July 2006 with corrections to the Cover Date.     

Potassium Iodide as a Chemical Actinometer for 254 nm Radiation: Use of lodate as an Electron Scavenger

Abstract— A solution of 0.6 M iodide and 0.1 M iodate in 0.01 M borate buffer (pH 9.25) can be used as a chemical actinometer to measure the incident fluence from a low-pressure mercury lamp that puts out more than 85% of its energy at 254 nm. The actinometric solution is optically opaque to light below 290 nm and is optically transparent to wavelengths greater than 330 nm. Hence, the solution absorbs all of the germicidal wavelengths but little if any of the ambient light normally present in the laboratory. Iodate acts as an electron scavenger and prevents the back reaction of the free electron with the iodine atom following UV excitation of KI. Irradiation results in the linear formation of triiodide, which is quantitated by measuring its absorbance at 352 nm. The quantum yield for this system is approximately 0.75 0.03 at 20.7A_oC or approximately three times greater than that obtained previously using nitrous oxide as an electron scavenger. A model is proposed to account for this difference. A precise expression to account for the concentration and temperature dependence of the quantum yield is given by pH = 0.75(1 + 0.23[C - 0.577])(1 + 0.02[T - 20.7]) where C is the concentration of iodide and T is the temperature. The concentration of iodide can be obtained from the absorbance at 300 nm prior to irradiation using 1.061 MJ cm⁻¹ as the molar extinction coefficient. This actinometric system meets the quality criteria established by the International Union of Pure and Applied Chemistry with the caveat that it is designed to measure only germicidal radiation (i.e. wavelengths less than 290 nm).     

ACTION SPECTRA FOR THE PHOTOLYSIS OF 5-IODODEOXYURIDINE IN DNA AND RELATED MODEL SYSTEMS: EVIDENCE FOR SHORT-RANGE ENERGY TRANSFER*

Abstract— A variety of polynucleotides containing 5-iodouracil residues were irradiated in aqueous solution with wavelengths between 240 and 313 nm. From the rate of deiodination the photochemical cross sections (a_B) were determined as a function of the irradiation wavelength (A). The expression was used to relate the observed values of _B to the intrinsic quantum yield, φ_INT, and to the absorption cross sections, and for the iodinated and noniodinated residues, respectively. φ_INT is the probability an excited iodouracil residue will deiodinate, while the parameter b is a measure of the number of noniodinated bases which contribute their excitation energy to the deiodination process. For IdUrd and poly(5-iodouridylic acid), the average values of φ_INT calculated from the experimental _B values were 0.0202 and 0.0188, respectively, for irradiation in air. In native, denatured, and depurinated DNA in which IdUrd was substituted for 10% of the Thd, the average φ_INT values were 0.0069, 0.0088, and 0.0153, respectively, indicating an enhancement in φ_INT upon decreasing the order of the polynucleotide. In contrast, the average values of b bor the same set of compounds were found to be 4 , 2 and 0.4, respectively, indicating a decrease in b with decreasing polynucleotide order, i.e. a loss of base stacking decreases the extent of energy transfer. A value of b= 4 for native DNA is assumed to mean that the extent of energy transfer in native DNA is limited to four base donors per iodouracil residue serving as an energy trap.     

PHOTOCHEMISTRY OF DNA CONTAINING IODINATED CYTOSINE*

Abstract— –Irradiation at 313 nm of compounds containing iodinated cytosine moieties results in the photolysis of iodine. Photolysis occurs with a quantum yield of 0·0224·024 for 5-iododeoxycytidine and 5-iododeoxycytidine monophosphate, and 0·004–0·008 for iodinated DNA as well as for iodinated polycytidylate. Photodegradation of the cytosine moiety occurs when air is present during irradiation, presumably due to the reaction of oxygen with the cytosyl radical formed when iodine is lost. This oxygen promoted photodegradation destroys the cytosine chromophore and is complete in the monomers but occurs to only a limited extent in the polymers. In the absence of oxygen or in the presence of ethanol, photodegradation is prevented and the loss of iodine leads exclusively to the formation of the cytosine chromophore. In DNA, the loss of iodine is accompanied by the formation of sugar damage and/or chain breaks. As measured by sedimentation in alkaline sucrose gradients, approximately one break is made for every six iodinqs lost in denatured DNA. The frequency of chain breakage per iodine photolyzed is reduced 2-fold in renatured DNA. Analysis in neutral gradients suggests that half of the breaks observed in alkali are alkali-labile bonds. Both ethanol and cysteamine reduce the number of chain breaks observed in alkali by ˜ 3-fold.     

QUANTUM YIELD OF PHOTOHYDRATION FOR DIMETHYLURACIL. CONCENTRATION AND WAVELENGTH DEPENDENCE*

Abstract— The quantum yields for the photohydration of dimethyluracil were determined for concentrations in the range 5 × 10^--¹-^-1 × 10^--³M by use of 240–280 nm irradiation. The average quantum yield (0.0139 f 0.0005) was independent of both concentration and irradiation wavelength.     

USE OF POTASSIUM IODIDE AS A CHEMICAL ACTINOMETER

Abstract Aqueous solutions of KI were examined for use as chemical actinometers to measure 254 nm (germicidal) radiation. Irradiation results in electron ejection from iodide such that aqueous electrons and iodine atoms are formed. In the presence of N₂0, an electron scavenger, recombination of these two reactive species is eliminated and stoi-chiometric formation of triiodide occurs. The absorbance increase due to triiodide was followed and the quantum yield determined using either a radiometer or ferrioxalate actinometry to estimate the amount of energy absorbed by the KI solution. The quantum yield ( ø ) at 25°C was determined to be 0.26 using radiometry, and 0.224–0.233 using actinometry, depending on the radiation conditions. The following expression was used to measure the incident Huence rate for 254 radiation at a given temperature T for irradiation over a time interval Δt (s) fluence rate (W/m²) = 4. 96 × 10⁶ΔOD(λ)/ e(λ) [0.23+0.004(T-25)] δ t cm⁻¹
At temperatures other than 25°C, the temperature dependence of the quantum yield (0.004/°C) is taken into account by the term shown in the denominator. Because KI remains relatively blind to longer wavelengths such as those found in normal room light, measurements can be made in the presence of room light without having to work in a darkened room.     

Quantum yield of the iodide-iodate chemical actinometer: dependence on wavelength and concentrations

The quantum yield (QY) of the iodide-iodate chemical actinometer (0.6 M KI-0.1 M KIO3) was determined for irradiation between 214 and 330 nm. The photoproduct, triiodide, was determined from the increase in absorbance at 352 nm, which together with a concomitant measurement of the UV fluence enabled the QY to be calculated. The QY at 254 nm was determined to be 0.73 +/- 0.02 when calibration was carried out against a National Institute of Standards and Technology traceable radiometer or photometric device. At wavelengths below 254 nm the QY increased slightly, leveling off at -0.80 +/- 0.05, whereas above 254 nm the QY decreases linearly with wavelength, reaching a value of 0.30 at 284 nm. In addition, the QY was measured at different iodide concentrations. There is a slight decrease in QY going from 0.6 to 0.15 M KI, whereas below 0.15 M KI the QY drops off sharply, decreasing to 0.23 by 0.006 M KI. Calibration of the QY was also done using potassium ferrioxalate actinometry to measure the irradiance. These results showed a 20% reduction in QY between 240 and 280 nm as compared with radiometry. This discrepancy suggests that the QY of the ferrioxalate actinometer in this region of the spectrum needs reexamination.     

ULTRAVIOLET IRRADIATION OF NUCLEIC ACIDS COMPLEXED WITH HEAVY ATOMS—III. INFLUENCE OF Ag + AND Hg 2+ ON THE SENSITIVITY OF PHAGE AND OF TRANSFORMING DNA TO ULTRAVIOLET RADIATION

Abstract— We have studied the influence of the heavy metal ions Ag⁺ and Hg²⁺ on the photoinactivation and photodimerization of transforming DNA and of bacteriophage. The rate of inactivation of Haemophilus influenzae transforming DNA by ultraviolet (UV) radiation was enhanced by a factor of 30 when it was complexed with Ag⁺. This enhancement was correlated with a comparable increase in the rate of thymine dimerization. In contrast, mercuric ions led to a reduction in the rates of both inactivation and dimerization. When we examined the effects of these metal ions on the photobiology of bacteriophage, we again found that Ag⁺ enhanced and Hg²⁺ reduced the rate of ultraviolet inactivation. These results demonstrate that heavy metals may be useful tools for studying the photochemistry and photobiology of nucleic acids.