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.     

A theoretical evidence for cooperativity effects in fluorine-centered halogen bonds: linear (FCN)2–7 and (FNC)2–7 clusters

A theoretical investigation was performed to study cooperative effects in fluorine-centered halogen bond interactions. We investigated geometry, strength, and origin of the interactions in linear (FCN)_2–7 and (FNC)_2–7 clusters by means of MP2 and CCSD(T) methods. Our results strongly suggest that cooperative effects induced by fluorine-centered halogen bonds are significant in both linear FCN and FNC clusters. CCSD(T)/6-311++G** calculations reveal that for (FCN)_2–7 clusters, the average halogen-bonding energy per monomer increases from ?0.76 kcal/mol in dimer to ?0.92 kcal/mol in heptamer. The results of electron density analysis suggest that the capacity of the linear FCN and FNC clusters to concentrate electrons at the F···N and F···C BCPs enhance considerably with cluster size. The results also indicate that the magnitude of cooperative effects is more important for FCN than for FNC clusters. According to energy decomposition analysis, attractive electrostatic and dispersion components make the major contribution to the F···N and F···C halogen bond interactions. An acceptable correlation is found between different energy terms and total interaction energies, revealing the main role of these interactions for stability of linear (FCN) _n and (FNC) _n clusters.     

Application of a dispersive micro‐solid‐phase extraction method for pre‐concentration and ultra‐trace determination of cadmium ions in water and biological samples

A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l^?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l^?1 and <6%, respectively.     

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.     

Acid‐induced homogenous liquid‐phase microextraction: Application of medium‐chain carboxylic acid as extraction phase

In this research, a novel homogeneous liquid‐phase microextraction method was successfully developed based on applying octanoic acid as low‐density extraction solvent. The method was applied for extraction and determination of chlorophenols (CPs) as model compounds. Twelve milliliter of the sample solution was poured into a home‐designed glass vial. Sixty microliter of octanoic acid was solved in water sample by adjusting pH and ionic strength. By rapid addition of 75 μL of concentrated HCl (6 M), a cloudy solution was obtained. Phase separation occurred at 5000 rpm for 5 min. After that, 20 μL of the collected phase (approximately 26 μL) was injected into the HPLC‐UV instrument for analysis. The effect of some parameters such as the volume of concentrated HCl (phase separation reagent), ionic strength, extraction time, centrifugation time, and the volume of extracting phase on the extraction efficiency of the CPs were investigated and optimized. The preconcentration factors in a range of 159–218 were obtained under the optimal conditions. The linear range, detection limits (S/N = 3), and precision (n = 3) were 1– 200, 0.3–0.5 μg/L, and 4.6–5.1%, respectively. Tap water, seawater, and river water samples were successfully analyzed for the existence of CPs using the proposed method and satisfactory results were obtained.     

Ultrasound-assisted emulsification microextraction using low density solvent for analysis of toxic nitrophenols in natural waters

An ultrasound-assisted emulsification microextraction (USAEME) based on low-density solvents was successfully applied for the extraction and pre-concentration of four toxic nitrophenols in water samples. The extracted analytes were analyzed by high-performance liquid chromatography-UV detection. The important parameters influencing the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time (OVAT) and central composite design (CCD). The results showed that the emulsification process can be completed in a few seconds using low-density solvents, but almost 10–20?min is necessary for high-density solvents. Under the optimum conditions (extraction solvent, 1-octanol; extraction solvent volume, 40?µL; sample pH, 3.0; salt concentration, 20% (w/v) NaCl; extraction temperature, 40 (±3)°C), limits of detection of the method were in the range of 0.25 to 1?µg?L^?1 and the repeatability and reproducibility of the proposed method, expressed as relative deviation, varied in the range of 2.2–4.2% and 4.7–6.9%, respectively. Linearity was found to be in the range of 1 to 200?µg?L^?1 and the preconcentration factors (PFs) were between 77 and 175. The relative recoveries of the four nitrophenols from water samples at spiking level of 10.0?µg?L^?1 were in the range of 92.0 to 115.0%.     

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.