A Cervid Vocal Fold Model Suggests Greater Glottal Efficiency in Calling at High Frequencies

Male Rocky Mountain elk (Cervus elaphus nelsoni) produce loud and high fundamental frequency bugles during the mating season, in contrast to the male European Red Deer (Cervus elaphus scoticus) who produces loud and low fundamental frequency roaring calls. A critical step in understanding vocal communication is to relate sound complexity to anatomy and physiology in a causal manner. Experimentation at the sound source, often difficult in vivo in mammals, is simulated here by a finite element model of the larynx and a wave propagation model of the vocal tract, both based on the morphology and biomechanics of the elk. The model can produce a wide range of fundamental frequencies. Low fundamental frequencies require low vocal fold strain, but large lung pressure and large glottal flow if sound intensity level is to exceed 70 dB at 10 m distance. A high-frequency bugle requires both large muscular effort (to strain the vocal ligament) and high lung pressure (to overcome phonation threshold pressure), but at least 10 dB more intensity level can be achieved. Glottal efficiency, the ration of radiated sound power to aerodynamic power at the glottis, is higher in elk, suggesting an advantage of high-pitched signaling. This advantage is based on two aspects; first, the lower airflow required for aerodynamic power and, second, an acoustic radiation advantage at higher frequencies. Both signal types are used by the respective males during the mating season and probably serve as honest signals. The two signal types relate differently to physical qualities of the sender. The low-frequency sound (Red Deer call) relates to overall body size via a strong relationship between acoustic parameters and the size of vocal organs and body size. The high-frequency bugle may signal muscular strength and endurance, via a ‘vocalizing at the edge’ mechanism, for which efficiency is critical

Carbon K-shell Photo Ionization of CO: Molecular frame angular Distributions of normal and conjugate shakeup Satellites

We have measured the molecular frame angular distributions of photoelectrons emitted from the Carbon K shell of fixed-in-space CO molecules for the case of simultaneous excitation of the remaining molecular ion. Normal and conjugate shake up states are observed. Photo electrons belonging to normal \Sigma -satellite lines show an angular distribution resembling that observed for the main photoline at the same electron energy. Surprisingly a similar shape is found for conjugate shake up states with \Pi -symmetry. In our data we identify shake rather than electron scattering (PEVE) as the mechanism producing the conjugate lines. The angular distributions clearly show the presence of a \Sigma -shape resonance for all of the satellite lines.Comment: 8 pages, 2 figure

Transfer ionization and its sensitivity to the ground-state wave function

We present kinematically complete theoretical calculations and experiments for transfer ionization in H$^++$He collisions at 630 keV/u. Experiment and theory are compared on the most detailed level of fully differential cross sections in the momentum space. This allows us to unambiguously identify contributions from the shake-off and two-step-2 mechanisms of the reaction. It is shown that the simultaneous electron transfer and ionization is highly sensitive to the quality of a trial initial-state wave function

Interatomic Coulombic Decay following Photoionization of the Helium Dimer: Observation of Vibrational Structure

Using synchrotron radiation we simultaneously ionize and excite one helium atom of a helium dimer (He_2) in a shakeup process. The populated states of the dimer ion (i.e. He^[*+](n = 2; 3)-He) are found to deexcite via interatomic coulombic decay. This leads to the emission of a second electron from the neutral site and a subsequent coulomb explosion. In this letter we present a measurement of the momenta of fragments that are created during this reaction. The electron energy distribution and the kinetic energy release of the two He^+ ions show pronounced oscillations which we attribute to the structure of the vibrational wave function of the dimer ion.Comment: 8 pages, 5 figure

Single photon double ionization of the helium dimer

We show that a single photon can ionize the two helium atoms of the helium dimer in a distance up to 10 {\deg}A. The energy sharing among the electrons, the angular distributions of the ions and electrons as well as comparison with electron impact data for helium atoms suggest a knock-off type double ionization process. The Coulomb explosion imaging of He_2 provides a direct view of the nuclear wave function of this by far most extended and most diffuse of all naturally existing molecules.Comment: 10 pages, 5 figure

Adapted to Roar: Functional Morphology of Tiger and Lion Vocal Folds

Vocal production requires active control of the respiratory system, larynx and vocal tract. Vocal sounds in mammals are produced by flow-induced vocal fold oscillation, which requires vocal fold tissue that can sustain the mechanical stress during phonation. Our understanding of the relationship between morphology and vocal function of vocal folds is very limited. Here we tested the hypothesis that vocal fold morphology and viscoelastic properties allow a prediction of fundamental frequency range of sounds that can be produced, and minimal lung pressure necessary to initiate phonation. We tested the hypothesis in lions and tigers who are well-known for producing low frequency and very loud roaring sounds that expose vocal folds to large stresses. In histological sections, we found that the Panthera vocal fold lamina propria consists of a lateral region with adipocytes embedded in a network of collagen and elastin fibers and hyaluronan. There is also a medial region that contains only fibrous proteins and hyaluronan but no fat cells. Young's moduli range between 10 and 2000 kPa for strains up to 60%. Shear moduli ranged between 0.1 and 2 kPa and differed between layers. Biomechanical and morphological data were used to make predictions of fundamental frequency and subglottal pressure ranges. Such predictions agreed well with measurements from natural phonation and phonation of excised larynges, respectively. We assume that fat shapes Panthera vocal folds into an advantageous geometry for phonation and it protects vocal folds. Its primary function is probably not to increase vocal fold mass as suggested previously. The large square-shaped Panthera vocal fold eases phonation onset and thereby extends the dynamic range of the voice

Ion impact induced Interatomic Coulombic Decay in neon and argon dimers

We investigate the contribution of Interatomic Coulombic Decay induced by ion impact in neon and argon dimers (Ne$_2$ and Ar$_2$) to the production of low energy electrons. Our experiments cover a broad range of perturbation strengths and reaction channels. We use 11.37 MeV/u S$^{14+}$, 0.125 MeV/u He$^{1+}$, 0.1625 MeV/u He$^{1+}$ and 0.150 MeV/u He$^{2+}$ as projectiles and study ionization, single and double electron transfer to the projectile as well as projectile electron loss processes. The application of a COLTRIMS reaction microscope enables us to retrieve the three-dimensional momentum vectors of the ion pairs of the fragmenting dimer into Ne$^{q+}$/Ne$^{1+}$ and Ar$^{q+}$/Ar$^{1+}$ (q = 1, 2, 3) in coincidence with at least one emitted electron