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.     

Stereoselective synthesis of unnatural α-amino acid derivatives through photoredox catalysis

A protocol for stereoselective C-radical addition to a chiral glyoxylate-derived N-sulfinyl imine was developed through visible light-promoted photoredox catalysis, providing a convenient method for the synthesis of unnatural α-amino acids. The developed protocol allows the use of ubiquitous carboxylic acids as radical precursors without prior derivatization. The protocol utilizes near-stoichiometric amounts of the imine and the acid radical precursor in combination with a catalytic amount of an organic acridinium-based photocatalyst. Alternative mechanisms for the developed transformation are discussed and corroborated by experimental and computational studies.

A protocol for stereoselective C-radical addition to a chiral glyoxylate-derived N-sulfinyl imine was developed through visible light-promoted photoredox catalysis, providing a convenient method for the synthesis of unnatural α-amino acids.     

Defect formation on surfaces bombarded by energetic multiply charged proteins: Implications for the conformation of gas-phase electrosprayed ions

Indirect information on the conformation of highly charged molecular ions may be obtained by monitoring their collisional cross sections and the course of simple gas-phase reactions such as hydrogen-deuterium exchange. In this work, another indirect but more visually oriented approach is explored: electrosprayed protein ions are accelerated toward a highly oriented pyrolytic graphite surface and the resulting single-ion defects are imaged by scanning force and tunneling microscopy. All protein impacts generated shallow hillocks: the shapes depended on the identity and charge state of the incident protein. Lysozyme and myoglobin, both compact, globular proteins in the native state, produced compact, almost circular hillocks. However, hillocks generated by myoglobin that had been denatured in the solution phase were elongated, and the elongation was positively correlated with the charge state of the ion. It appears that structural information about gas-phase multiply charged proteins can be derived from imprints generated by energetic protein impacts on surfaces.     

Electron capture dissociation of substance P using a commercially available Fourier transform ion cyclotron resonance mass spectrometer

Electron capture dissociation of the peptide Substance P is reported for the first time, with an unmodified, commercially available Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. The fragmentation pattern is compared with that obtained with collisionally induced dissociation of the ions in the electrospray ion source, and note that electron capture dissociation gives a more easily interpreted spectrum, showing mainly C-fragments. With the exception of the proline residues, which require cleavage of two chemical bonds, we observe all C-fragmental we find the bias voltage of the electron gun not to be very critical.     

Superporous agarose beads as a hydrophobic interaction chromatography support

Superporous agarose beads were used as a support for hydrophobic interaction chromatography. These beads have large connecting flow pores in addition to their normal diffusion pores. The flow pores, which are approximately one fifth of the overall diameter of the superporous agarose beads, were earlier shown to give the beads improved mass transfer properties relative to homogeneous agarose beads (Gustavsson and Larsson, J. Chromatogr. A, 734 (1996) 231–240). Superporous agarose beads and homogeneous agarose beads of the same particle size range (106–180 μm) were derivatized with phenyl groups. The properties of the superporous beads were then compared with the homogeneous beads in the separation of a mixture of three model proteins (ribonuclease A, lysozyme and bovine serum albumin) at various superficial flow velocities from 30 to 600 cm/h. The superporous beads gave satisfactory separation at flow velocities five times higher than was possible for homogeneous beads. The performance of the two types of beads was also compared in the purification of lactate dehydrogenase from a beef heart extract at a superficial flow velocity of 150 cm/h. The superporous beads performed considerably better, leading to twice the purification factor and twice the concentration of the desired product. The results were interpreted using the theoretical treatment given by Carta and Rodrigues (Carta and Rodrigues, Chem. Eng. Sci., 48 (1993) 3927).     

Comparison of preconditioned Krylov subspace iteration methods for PDE-constrained optimization problems

The governing dynamics of fluid flow is stated as a system of partial differential equations referred to as the Navier-Stokes system. In industrial and scientific applications, fluid flow control becomes an optimization problem where the governing partial differential equations of the fluid flow are stated as constraints. When discretized, the optimal control of the Navier-Stokes equations leads to large sparse saddle point systems in two levels. In this paper, we consider distributed optimal control for the Stokes system and test the particular case when the arising linear system can be compressed after eliminating the control function. In that case, a system arises in a form which enables the application of an efficient block matrix preconditioner that previously has been applied to solve complex-valued systems in real arithmetic. Under certain conditions, the condition number of the so preconditioned matrix is bounded by 2. The numerical and computational efficiency of the method in terms of number of iterations and execution time is favorably compared with other published methods.     

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.     

A Practical Procedure for the Solid-Phase Synthesis of Racemic 2,2′-Dihydroxy-1,1′-binaphthyl

Abstract: A high yielding solid-phase dimerisation of 2-naphthol by means of a ball-milling procedure is described.