A longitudinal study of intonation in an a cappella singing quintet

Objective The skill to control pitch accurately is an important feature of performance in singing ensembles as it boosts musical excellence. Previous studies analyzing single performance sessions provide inconclusive and contrasting results on whether singers in ensembles tend to use a tuning system which deviates from equal temperament for their intonation. The present study observes the evolution of intonation in a newly formed student singing quintet during their first term of study. Methods/Design A semiprofessional singing quintet was recorded using head-worn microphones and electrolaryngograph electrodes to allow fundamental frequency (fo) evaluation of the individual voices. In addition, a camcorder was used to record verbal interactions between singers. The ensemble rehearsed a homophonic piece arranged for the study during five rehearsal sessions over four months. Singers practiced the piece for 10 minutes in each rehearsal, and performed three repetitions of the same pieces pre-rehearsal and post-rehearsal. Audio and electrolaryngograph data of the repeated performances, and video recordings of the rehearsals were analyzed. Aspects of intonation were then measured by extracting the fo values from the electrolaryngograph and acoustic signal, and compared within rehearsals (pre and post) and between rehearsals (rehearsals 1 to 5), and across repetitions (take 1 to 3). Time-stamped transcriptions of rehearsal discussions were used to identify verbal interactions related to tuning, the tuning strategies adopted, and their location (bar or chord) within the piece. Results/Discussion Tuning of each singer was closer to equal temperament than just intonation, but the size of major thirds was slightly closer to just intonation, and minor thirds closer to equal temperament. These findings were consistent within and between rehearsals, and across repetitions. Tuning was highlighted as an important feature of rehearsal during the study term, and a range of strategies were adopted to solve tuning related issues. This study provides a novel holistic assessment of tuning strategies within a singing ensemble, furthering understanding of performance practices as well as revealing the complex approach needed for future research in this area. These findings are particularly important for directors and singers to tailor rehearsal strategies that address tuning in singing ensembles, showing that approaches need to be context driven rather than based on theoretical ideal

Molecular dynamics simulation of classical sound absorption in a monatomic gas

Sound wave propagation in argon gas is simulated usingmolecular dynamics (MD) in order to determine the attenuation of acoustic energy due to classical (viscous and thermal) losses at high frequencies. In addition, amethod is described to estimate attenuation of acoustic energy using the thermodynamic concept of exergy. The results are compared against standing wave theory and the predictions of the theory of continuum mechanics. Acoustic energy losses are studied by evaluating various attenuation parameters and by comparing the changes in behavior at three different frequencies. This study demonstrates acoustic absorption effects in a gas simulated in a thermostatted molecular simulation and quantifies the classical losses in terms of the sound attenuation constant. The approach can be extended to further understanding of acoustic loss mechanisms in the presence of nanoscale porous materials in the simulation domain.M. Ayub, A.C. Zander, D.M. Huang, B.S. Cazzolato, C.Q. Howar

Molecular dynamics simulations of acoustic absorption by a carbon nanotube

Acoustic absorption by a carbon nanotube (CNT) was studied using molecular dynamics (MD) simulations in a molecular domain containing a monatomic gas driven by a time-varying periodic force to simulate acoustic wave propagation. Attenuation of the sound wave and the characteristics of the sound field due to interactions with the CNT were studied by evaluating the behavior of various acoustic parameters and comparing the behavior with that of the domain without the CNT present. A standing-wave model was developed for the CNT-containing system to predict sound attenuation by the CNT and the results were verifi ed against estimates of attenuation using the thermodynamic concept of exergy. This study demonstrates acoustic absorption effects of a CNT in a thermostatted MD simulation, quanti es the acoustic losses induced by the CNT and illustrates their effects on the CNT. Overall, a platform was developed for MD simulations that can model acoustic damping induced by nanostructured materials such as CNTs, which can be used to further understanding of nanoscale acoustic loss mechanisms associated with molecular interactions between acoustic waves and nanomaterials.M. Ayub, A. C. Zander, D. M. Huang, C. Q. Howard and B. S. Cazzolat

Single Spin Measurement using Single Electron Transistors to Probe Two Electron Systems

We present a method for measuring single spins embedded in a solid by probing two electron systems with a single electron transistor (SET). Restrictions imposed by the Pauli Principle on allowed two electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well suited to measure. We focus on a particular system capable of being fabricated with current technology: a Te double donor in Si adjacent to a Si/SiO2 interface and lying directly beneath the SET island electrode, and we outline a measurement strategy capable of resolving single electron and nuclear spins in this system. We discuss the limitations of the measurement imposed by spin scattering arising from fluctuations emanating from the SET and from lattice phonons. We conclude that measurement of single spins, a necessary requirement for several proposed quantum computer architectures, is feasible in Si using this strategy.Comment: 22 Pages, 8 Figures; revised version contains updated references and small textual changes. Submitted to Phys. Rev.

A Parametric Study of Erupting Flux Rope Rotation. Modeling the "Cartwheel CME" on 9 April 2008

The rotation of erupting filaments in the solar corona is addressed through a parametric simulation study of unstable, rotating flux ropes in bipolar force-free initial equilibrium. The Lorentz force due to the external shear field component and the relaxation of tension in the twisted field are the major contributors to the rotation in this model, while reconnection with the ambient field is of minor importance. Both major mechanisms writhe the flux rope axis, converting part of the initial twist helicity, and produce rotation profiles which, to a large part, are very similar in a range of shear-twist combinations. A difference lies in the tendency of twist-driven rotation to saturate at lower heights than shear-driven rotation. For parameters characteristic of the source regions of erupting filaments and coronal mass ejections, the shear field is found to be the dominant origin of rotations in the corona and to be required if the rotation reaches angles of order 90 degrees and higher; it dominates even if the twist exceeds the threshold of the helical kink instability. The contributions by shear and twist to the total rotation can be disentangled in the analysis of observations if the rotation and rise profiles are simultaneously compared with model calculations. The resulting twist estimate allows one to judge whether the helical kink instability occurred. This is demonstrated for the erupting prominence in the "Cartwheel CME" on 9 April 2008, which has shown a rotation of \approx 115 degrees up to a height of 1.5 R_sun above the photosphere. Out of a range of initial equilibria which include strongly kink-unstable (twist Phi=5pi), weakly kink-unstable (Phi=3.5pi), and kink-stable (Phi=2.5pi) configurations, only the evolution of the weakly kink-unstable flux rope matches the observations in their entirety.Comment: Solar Physics, submitte

Zero-point vacancies in quantum solids

A Jastrow wave function (JWF) and a shadow wave function (SWF) describe a quantum solid with Bose--Einstein condensate; i.e. a supersolid. It is known that both JWF and SWF describe a quantum solid with also a finite equilibrium concentration of vacancies x_v. We outline a route for estimating x_v by exploiting the existing formal equivalence between the absolute square of the ground state wave function and the Boltzmann weight of a classical solid. We compute x_v for the quantum solids described by JWF and SWF employing very accurate numerical techniques. For JWF we find a very small value for the zero point vacancy concentration, x_v=(1.4\pm0.1) x 10^-6. For SWF, which presently gives the best variational description of solid 4He, we find the significantly larger value x_v=(1.4\pm0.1) x 10^-3 at a density close to melting. We also study two and three vacancies. We find that there is a strong short range attraction but the vacancies do not form a bound state.Comment: 19 pages, submitted to J. Low Temp. Phy

Coronal Shock Waves, EUV Waves, and Their Relation to CMEs. III. Shock-Associated CME/EUV Wave in an Event with a Two-Component EUV Transient

On 17 January 2010, STEREO-B observed in extreme ultraviolet (EUV) and white light a large-scale dome-shaped expanding coronal transient with perfectly connected off-limb and on-disk signatures. Veronig et al. (2010, ApJL 716, 57) concluded that the dome was formed by a weak shock wave. We have revealed two EUV components, one of which corresponded to this transient. All of its properties found from EUV, white light, and a metric type II burst match expectations for a freely expanding coronal shock wave including correspondence to the fast-mode speed distribution, while the transient sweeping over the solar surface had a speed typical of EUV waves. The shock wave was presumably excited by an abrupt filament eruption. Both a weak shock approximation and a power-law fit match kinematics of the transient near the Sun. Moreover, the power-law fit matches expansion of the CME leading edge up to 24 solar radii. The second, quasi-stationary EUV component near the dimming was presumably associated with a stretched CME structure; no indications of opening magnetic fields have been detected far from the eruption region.Comment: 18 pages, 10 figures. Solar Physics, published online. The final publication is available at http://www.springerlink.co

Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter

The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift and line width simultaneously in a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of CME initiation and propagation. Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space weather monitoring.Comment: 6 figures. Will appear in the special issue of Coronal Magnetism, Sol. Phy

Red Queen Coevolution on Fitness Landscapes

Species do not merely evolve, they also coevolve with other organisms. Coevolution is a major force driving interacting species to continuously evolve ex- ploring their fitness landscapes. Coevolution involves the coupling of species fit- ness landscapes, linking species genetic changes with their inter-specific ecological interactions. Here we first introduce the Red Queen hypothesis of evolution com- menting on some theoretical aspects and empirical evidences. As an introduction to the fitness landscape concept, we review key issues on evolution on simple and rugged fitness landscapes. Then we present key modeling examples of coevolution on different fitness landscapes at different scales, from RNA viruses to complex ecosystems and macroevolution.Comment: 40 pages, 12 figures. To appear in "Recent Advances in the Theory and Application of Fitness Landscapes" (H. Richter and A. Engelbrecht, eds.). Springer Series in Emergence, Complexity, and Computation, 201