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Johannes Baumgart

Johannes Baumgart
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Doctor of Engineering

About

38
Publications
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559
Citations
Introduction

Publications

Publications (38)
Article
The infrasound levels due to the blade-tower interaction generated by a wind turbine in the publication by Pilger and Ceranna (JSV, Vol. 388, pp. 188–200, 2017) have to be corrected to be interpreted as sound pressure level. Also, the electrical power of the wind turbine should be corrected for the high wind case to 660 kW. We provide a reanalysis...
Preprint
Full-text available
The infrasound levels due to the blade-tower interaction generated by a wind turbine in the publication by Pilger and Ceranna (JSV, Vol. 388, pp. 188-200, 2017) have to be corrected to be interpreted as sound pressure level. Also, the electrical power of the wind turbine should be corrected for the high wind case to 660 kW. We provide a reanalysis...
Article
Full-text available
Noise from wind turbines (WTG) affects people. In order to understand how, knowledge of the relationships between sound generation, propagation, perception and assessment is essential. The key noise source of modern wind turbines is the motion of the rotor blades through the air. Different mechanisms generate the noise, which has a broadband charac...
Article
Full-text available
During mitosis, the centrosome expands its capacity to nucleate microtubules. Understanding the mechanisms of centrosomal microtubule nucleation is, however, constrained by a lack of knowledge of the amount of soluble and polymeric tubulin at mitotic centrosomes. Here we combined light microscopy and serial-section electron tomography to measure th...
Preprint
Full-text available
During mitosis, the centrosome expands its capacity to nucleate microtubules. Understanding the mechanisms of centrosomal microtubule nucleation is, however, constrained by a lack of knowledge of the amount of soluble and polymer tubulin at mitotic centrosomes. Here we combined light microscopy and serial-section electron tomography to measure the...
Article
Chemically active droplets are nonequilibrium systems that combine phase separation with chemical reactions. We here investigate how the activity introduced by the chemical reactions influences solid particles inside such droplets. We find that passive particles are centered in active droplets governed by first-order reactions. In autocatalytic act...
Article
Full-text available
The mitotic spindle ensures the faithful segregation of chromosomes. Here we combine the first large-scale serial electron tomography of whole mitotic spindles in early C. elegans embryos with live-cell imaging to reconstruct all microtubules in 3D and identify their plus- and minus-ends. We classify them as kinetochore (KMTs), spindle (SMTs) or as...
Data
Visualization of the 3D reconstruction of a complete metaphase spindle in the early C. elegans embryo. This full reconstruction (corresponding to Figure 1a) shows KMTs in red, and both AMTs and SMTs in green. The segmentation of the chromosomes is shown in blue.
Data
Fluorescence recovery after photobleaching (FRAP) in C. elegans metaphase. The FRAP experiment (corresponding to Figure 4c) in a histone::GFP and γ-tubulin::GFP tagged C. elegans embryo in metaphase shows the recovery of the bleachmark over time. The exposure time is 100 ms, the frame rate is 2 frames per second.
Data
Visualization of microtubule plus-end growth in the metaphase spindle by EBP-2::GFP. This movie (corresponding to Figure 4a,b) shows two examples of the motion of EBP-2::GFP comets in metaphase of the early C.elegans embryo. The exposure is 150 ms, the frame rate is 5 frames per second.
Data
Laser microsurgery in the C. elegans metaphase spindle. Laser microsurgery in a γ-tubulin::GFP tagged C. elegans embryos was applied to induce the formation of novel microtubule plus and minus-ends. A single wave of microtubule depolymerisation can be observed. The exposure time is 300 ms and the frame rate is 1 frame every 5 seconds.
Data
Close up-view of the chromosome region of a metaphase spindle in the early C. elegans embryo. This movie (corresponding to Figure 1a) shows a close up-view of the microtubules around the metaphase plate. The rotation around the spindle axis shows KMTs in red, and both AMTs and SMTs in green. Chromosomes are visualized in blue.
Article
Full-text available
The mitotic spindle ensures the faithful segregation of chromosomes. Here we combine the first large-scale serial electron tomography of whole mitotic spindles in early C. elegans embryos with live-cell imaging to reconstruct all microtubules in 3D and identify their plus- and minus-ends. We classify them as kinetochore (KMTs), spindle (SMTs) or as...
Preprint
Full-text available
The mitotic spindle ensures the faithful segregation of chromosomes. To discover the nature of the crucial centrosome-to-chromosome connection during mitosis, we combined the first large-scale serial electron tomography of whole mitotic spindles in early C. elegans embryos with live-cell imaging. Using tomography, we reconstructed the positions of...
Article
Full-text available
The cochlear amplifier that provides our hearing with its extraordinary sensitivity and selectivity is thought to be the result of an active biomechanical process within the sensory auditory organ, the organ of Corti. Although imaging techniques are developing rapidly, it is not currently possible, in a fully active cochlea, to obtain detailed meas...
Article
In reed woodwinds, the pitch of a sound is the result of an interaction between the air column, the reed, and the player. The air column is well described by its resonance frequencies and their damping. The reed is a pressure-controlled valve, which drives a coupled oscillation that settles with a fundamental frequency near a resonance frequency of...
Article
The myriad creatures that inhabit the waters of our planet all swim using different mechanisms. Now, a simple relation links key physical observables of underwater locomotion, on scales ranging from millimetres to tens of metres.
Conference Paper
Full-text available
The cochlea is an organ of the hearing system, whose basic function is to map sounds of different frequencies onto corresponding characteristic positions along the basilar membrane (BM). Sound-induced BM vibration is transformed into deflection of stereocilia on the hair cells, which then encodes the sound as neural signals for perception. Most coc...
Conference Paper
Full-text available
Most cochlear models used to describe the basilar membrane vibration along the cochlea are concerned with macromechanics, and often assume that the organ of Corti moves as a single unit, ignoring the individual motion of different components. New experimental technologies provide the opportunity to measure the dynamic behaviour of different compone...
Article
Full-text available
Morphometry of the lamina reticularis of the guinea pig cochlea was performed using scanning electron microscopy. Seventy-four geometrical parameters of the lamina reticularis, the bundles of stereocilia, and individual stereocilia, in all rows of hair cells and within the individual hair cells, were measured at ten equally spaced locations along t...
Article
Full-text available
Metaphase spindles are microtubule-based structures that use a multitude of proteins to modulate their morphology and function. Today, we understand many details of microtubule assembly, the role of microtubule-associated proteins, and the action of molecular motors. Ultimately, the challenge remains to understand how the collective behaviour of th...
Preprint
The detection of sound begins when energy derived from acoustic stimuli deflects the hair bundles atop hair cells. As hair bundles move, the viscous friction between stereocilia and the surrounding liquid poses a fundamental challenge to the ear's high sensitivity and sharp frequency selectivity. Part of the solution to this problem lies in the act...
Article
Full-text available
The viscous liquid surrounding a hair bundle dissipates energy and dampens oscillations, which poses a fundamental physical challenge to the high sensitivity and sharp frequency selectivity of hearing. To identify the mechanical forces at play, we constructed a detailed finite-element model of the hair bundle. Based on data from the hair bundle of...
Article
Full-text available
The detection of sound begins when energy derived from an acoustic stimulus deflects the hair bundles on top of hair cells. As hair bundles move, the viscous friction between stereocilia and the surrounding liquid poses a fundamental physical challenge to the ear's high sensitivity and sharp frequency selectivity. Part of the solution to this probl...
Article
Full-text available
The computation of entry problems into a planetary atmosphere strongly relies on the models used to describe the thermal and chemical nonequilibrium effects in the flow, the radiation phenomenom, and the surface chemistry. Moreover, the solution of the flow field in the continuum approach also requires an accurate description of the transport prope...
Article
In the subtectorial space, momentum is transported by the fluid to the stereocilia of the inner hair cell (IHC), resulting in bending of the hair bundle. The fluid must pass through the v-shaped arrangement of the outer hair cell (OHC) stereocilia and is "squeezed" between the tectorial membrane (TM) and the reticular lamina, especially due to the...
Article
The modeling of the mechanical process of hearing requires an accurate geometrical model of the inner ear (cochlea). The purpose of this study was the creation of a 3-D model of the fluid chambers of Guinea pig cochlea, which could serve as a basis for further mechanical modeling. Micro computer tomography used in this study is a noninvasive method...
Article
The bocal of a bassoon is characterized by geometrical parameters such as the bore, the outer contour and the wall-thickness as well as material parameters and the coating. Professional bassoonists select bocals extremely carefully and report influences on the playability and sound colour. In order to understand the underlying effects, several expe...
Article
Full-text available
The solution of time-harmonic acoustic problems suffers from a frequency dependency which usually requires to solve the systems for many discrete frequencies independently. Among others, the Padé-via-Lanczos approximation provides an efficient solution. Herein, this method is applied to the external acoustic problem by using a finite and infinite e...
Article
The inner ear is filled with endolymph and perilymph, flu-ids which have mechanical properties comparable to water. The organ of corti is embedded in these fluids. The pres-sure fluctuations, which are transferred from outside by the outer, middle and inner ear, are acting finally on the stere-ocilia. It is still not fully understood what are the c...
Article
The discussed topic of isolating certain parameters which describe the timbre in connection with bocals of bassoons is of major interest for manufacturers and artist likewise since a reduction in the overall shear stress of these kinds of technical diffusors is very helpful but not sufficient. The timbre seen from the side of the musician has to be...
Article
Full-text available
Up to now, the Martian atmosphere has been modeled by a pure carbon dioxide mixture at VKI. A more comprehensive approach employs the addition of argon and nitrogen compounds. The real composition of the mixture in the aerobreaking altitude is estimated to be the same as on the ground level. The transport properties do almost not differ when the mi...

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