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Search Results: 1 - 10 of 224621 matches for " Ingo R. Titze "
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A Cervid Vocal Fold Model Suggests Greater Glottal Efficiency in Calling at High Frequencies
Ingo R. Titze,Tobias Riede
PLOS Computational Biology , 2010, DOI: 10.1371/journal.pcbi.1000897
Abstract: 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.
Adapted to Roar: Functional Morphology of Tiger and Lion Vocal Folds
Sarah A. Klemuk, Tobias Riede, Edward J. Walsh, Ingo R. Titze
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0027029
Abstract: 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.
A Multiwell Disc Appliance Used to Deliver Quantifiable Accelerations and Shear Stresses at Sonic Frequencies
Sarah A. Klemuk,Sarah Vigmostad,Kalyan Endapally,Andrew P. Wagner,Ingo R. Titze
Processes , 2014, DOI: 10.3390/pr2010071
Abstract: To mimic in vivo vibration of vocal fold cells, we studied the controllability and range of frequency, acceleration, duration, and shear stress in a new bioreactor attachment. The custom multiwell disc appliance fits into a commercially built rheometer, together termed a torsional rheometer bioreactor (TRB). Previous attachments to the TRB were capable of 50–100 Hz vibrations at relatively high strains but were limited to single-sample experiments. The TRB-multiwell disc system accommodates 20 samples in partially fluid-filled wells in an aseptic environment delivering three different acceleration conditions to different samples simultaneously. Frequency and amplitude used to calculate acceleration along with duration and shear stress were controllable and quantifiable using a combination of built-in rheometer sensors, manufacturer software, and smooth particle hydrodynamics (SPH) simulations. Computed shear stresses at the well bottom using SPH in two and three dimensions were verified with analytical approximations. Results demonstrate capabilities of the TRB-multiwell disc system that, when combined with computational modeling, provide quantifiable vibration parameters covering frequencies 0.01–250 Hz, accelerations of 0.02–300 m/s 2, and shear stresses of 0.01–1.4 Pa. It is well-suited for studying cell function underlying vocal fold lamina propria homeostasis, inflammation, and wound healing under differential vibration conditions.
Development of a Bikeability Index to Assess the Bicycle-Friendliness of Urban Environments  [PDF]
Patricia Jasmin Krenn, Pekka Oja, Sylvia Titze
Open Journal of Civil Engineering (OJCE) , 2015, DOI: 10.4236/ojce.2015.54045
Abstract: Background: Cycling as a means of transport contributes to public health in terms of increasing the physical activity behaviour and reducing air pollution. In comparison to walking, cycling-spe cific environmental characteristics have been less investigated. The aim of this study was to develop, based on geographic information systems (GIS) data, a bikeability index for a mid-sized European city, to examine the predictive validity of the index and to visualize the bicycle-friendliness of the city by creating a bikeability map. Methods: Using GIS data, we assessed the environmental characteristics of 278 bicycle trips in the city of Graz, Austria. Characteristics which differed significantly between the actually taken and shortest possible routes were used to form an additive bikeability index and the bikeability map for 100 m × 100 m cells. The relationship between the cycling behaviour and the bikeability index around the home environment was examined to assess the predictive validity of the index. Results: Three environmental components (cycling infrastructure, bicycle pathways and green areas) were positively related, and two components (main roads, and topography) were negatively related to the actually used route. These components formed the bikeability index, which was positively correlated with cycling behaviour (OR: 1.08, 95% CI 1.01 - 1.17). The final outcome is a high-resolution coloured map indicating the degree of bicycle-friendliness in the city of Graz. Conclusion: Mapping based on the bikeability index helps to visualize the bicycle-friendliness of an urban area. Therefore, it should be a useful tool for the planning as well as for the evaluation of the transport environments in cities.
Poeciliid male mate preference is influenced by female size but not by fecundity
Luis R. Arriaga,Ingo Schlupp
PeerJ , 2015, DOI: 10.7717/peerj.140
Abstract: While female mate preference is very well studied, male preference has only recently begun to receive significant attention. Its existence is found in numerous taxa, but empirical research has mostly been limited to a descriptive level and does not fully address the factors influencing its evolution. We attempted to address this issue using preference functions by comparing the strength of male preference for females of different sizes in nine populations of four poeciliid species. Due to environmental constraints (water toxicity and surface versus cave habitat), females from these populations vary in the degree to which their size is correlated to their fecundity. Hence, they vary in how their size signals their quality as mates. Since female size is strongly correlated with fecundity in this subfamily, males were sequentially presented with conspecific females of three different size categories and the strength of their preference for each was measured. Males preferred larger females in all populations, as predicted. However, the degree to which males preferred each size category, as measured by association time, was not correlated with its fecundity. In addition, cave males discriminated against smaller females more than surface males. Assuming that male preference is correlated with female fitness, these results suggest that factors other than fecundity have a strong influence on female fitness in these species.
The logarithmic triplet theory with boundary
Matthias R Gaberdiel,Ingo Runkel
Mathematics , 2006, DOI: 10.1088/0305-4470/39/47/016
Abstract: The boundary theory for the c=-2 triplet model is investigated in detail. In particular, we show that there are four different boundary conditions that preserve the triplet algebra, and check the consistency of the corresponding boundary operators by constructing their OPE coefficients explicitly. We also compute the correlation functions of two bulk fields in the presence of a boundary, and verify that they are consistent with factorisation.
From boundary to bulk in logarithmic CFT
Matthias R. Gaberdiel,Ingo Runkel
Mathematics , 2007, DOI: 10.1088/1751-8113/41/7/075402
Abstract: The analogue of the charge-conjugation modular invariant for rational logarithmic conformal field theories is constructed. This is done by reconstructing the bulk spectrum from a simple boundary condition (the analogue of the Cardy `identity brane'). We apply the general method to the c_1,p triplet models and reproduce the previously known bulk theory for p=2 at c=-2. For general p we verify that the resulting partition functions are modular invariant. We also construct the complete set of 2p boundary states, and confirm that the identity brane from which we started indeed exists. As a by-product we obtain a logarithmic version of the Verlinde formula for the c_1,p triplet models.
Gerbe-holonomy for surfaces with defect networks
Ingo Runkel,Rafal R. Suszek
Mathematics , 2008,
Abstract: We define the sigma-model action for world-sheets with embedded defect networks in the presence of a three-form field strength. We derive the defect gluing condition for the sigma-model fields and their derivatives, and use it to distinguish between conformal and topological defects. As an example, we treat the WZW model with defects labelled by elements of the centre Z(G) of the target Lie group G; comparing the holonomy for different defect networks gives rise to a 3-cocycle on Z(G). Next, we describe the factorisation properties of two-dimensional quantum field theories in the presence of defects and compare the correlators for different defect networks in the quantum WZW model. This, again, results in a 3-cocycle on Z(G). We observe that the cocycles obtained in the classical and in the quantum computation are cohomologous.
Affine su(2) fusion rules from gerbe 2-isomorphisms
Ingo Runkel,Rafal R. Suszek
Mathematics , 2009, DOI: 10.1016/j.geomphys.2011.03.008
Abstract: We give a geometric description of the fusion rules of the affine Lie algebra su(2)_k at a positive integer level k in terms of the k-th power of the basic gerbe over the Lie group SU(2). The gerbe can be trivialised over conjugacy classes corresponding to dominant weights of su(2)_k via a 1-isomorphism. The fusion-rule coefficients are related to the existence of a 2-isomorphism between pullbacks of these 1-isomorphisms to a submanifold of SU(2) x SU(2) determined by the corresponding three conjugacy classes. This construction is motivated by its application in the description of junctions of maximally symmetric defect lines in the Wess-Zumino-Witten model.
Comparative study of the electronic structures of the In and Sn/In2O3 (111) interfaces
M. Nazarzahdemoafi,F. Titze,S. Machulik,C. Janowitz,Z. Galazka,R. Manzke,M. Mulazzi
Physics , 2015,
Abstract: The electronic structure of the transparent semiconductor In2O3 has been studied by angle resolved photoemission spectroscopy upon deposition of metallic indium and also tin on the surface of the semiconductor. By deposition of metallic indium on In2O3 (111) single crystals, we detected the formation of a free-electron like band of effective mass (0.38+-0.05) m0. At low coverages, metallic In shifts the Fermi level of In2O3 to higher energies and a new electronic state forms at the metal/semiconductor interface. This state of two-dimensional character (2D-electron gas) is completely responsible for the electrical conduction in In2O3 (111) at the surface region and has a band dispersion, which does not correspond to the previously found surface accumulation layers in this material. Despite the similarity of the electronic properties of In and Sn, a larger downward banding was observed by Sn coverage, which was not accompanied by the appearance of the surface state.
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