232 research outputs found
First person â Agathe Chaigne
First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Agathe Chaigne is first author on â Three-dimensional geometry controls division symmetry in stem cell coloniesâ, published in JCS. Agathe is a postdoc in the lab of Ewa Paluch at the MRC Laboratory for Molecular Cell Biology (LMCB), University College London, London, UK, investigating the crosstalk between cell division and cell fate transitions during development
Active mesh and neural network pipeline for cell aggregate segmentation
Segmenting cells within cellular aggregates in 3D is a growing challenge in cell biology due to improvements in capacity and accuracy of microscopy techniques. Here, we describe a pipeline to segment images of cell aggregates in 3D. The pipeline combines neural network segmentations with active meshes. We apply our segmentation method to cultured mouse mammary gland organoids imaged over 24 h with oblique plane microscopy, a high-throughput light-sheet fluorescence microscopy technique. We show that our method can also be applied to images of mouse embryonic stem cells imaged with a spinning disc microscope. We segment individual cells based on nuclei and cell membrane fluorescent markers, and track cells over time. We describe metrics to quantify the quality of the automated segmentation. Our segmentation pipeline involves a Fiji plugin that implements active mesh deformation and allows a user to create training data, automatically obtain segmentation meshes from original image data or neural network prediction, and manually curate segmentation data to identify and correct mistakes. Our active meshes-based approach facilitates segmentation postprocessing, correction, and integration with neural network prediction
Response of an artificially blown clarinet to different blowing pressure profiles
Using an artificial mouth with an accurate pressure control, the onset of the
pressure oscillations inside the mouthpiece of a simplified clarinet is studied
experimentally. Two time profiles are used for the blowing pressure: in a first
set of experiments the pressure is increased at constant rates, then decreased
at the same rate. In a second set of experiments the pressure rises at a
constant rate and is then kept constant for an arbitrary period of time. In
both cases the experiments are repeated for different increase rates. Numerical
simulations using a simplified clarinet model blown with a constantly
increasing mouth pressure are compared to the oscillating pressure obtained
inside the mouthpiece. Both show that the beginning of the oscillations appears
at a higher pressure values than the theoretical static threshold pressure, a
manifestation of bifurcation delay. Experiments performed using an interrupted
increase in mouth pressure show that the beginning of the oscillation occurs
close to the stop in the increase of the pressure. Experimental results also
highlight that the speed of the onset transient of the sound is roughly the
same, independently of the duration of the increase phase of the blowing
pressure.Comment: 14 page
Intuitive control of rolling sound synthesis
International audienceThis paper presents a rolling sound synthesis model which can be intuitively controlled. To propose this model, different aspects of the rolling phenomenon are explored : physical modeling, perceptual attributes and signal morphology. A source-filter model for rolling sounds synthesis is presented with associated intuitive controls
Artificially decreasing cortical tension generates aneuploidy in mouse oocytes
Human and mouse oocytesâ developmental potential can be predicted by their mechanical
properties. Their development into blastocysts requires a specific stiffness window. In this
study, we combine live-cell and computational imaging, laser ablation, and biophysical
measurements to investigate how deregulation of cortex tension in the oocyte contributes to
early developmental failure. We focus on extra-soft cells, the most common defect in a
natural population. Using two independent tools to artificially decrease cortical tension, we
show that chromosome alignment is impaired in extra-soft mouse oocytes, despite normal
spindle morphogenesis and dynamics, inducing aneuploidy. The main cause is a cytoplasmic
increase in myosin-II activity that could sterically hinder chromosome capture. We describe
here an original mode of generation of aneuploidies that could be very common in oocytes
and could contribute to the high aneuploidy rate observed during female meiosis, a leading
cause of infertility and congenital disorders
Finite Element Modeling of Airflow During Phonation
International audienceIn the paper a mathematical model of airflow in human vocal folds is presented. The geometry of the glottal channel is based on measurements of excised human larynges. The airflow is modeled by nonstationary incompressible Navier-Stokes equations in a 2D computational domain, which is deformed in time due to vocal fold vibration. The paper presents numerical results and focuses on flow separation in glottis. Quantitative data from numerical simulations are compared to results of measurements by Particle Image Velocimetry (PIV), performed on a scaled self-oscillating physical model of vocal folds
Observation of wave turbulence in vibrating plates
The nonlinear interaction of waves in a driven medium may lead to wave
turbulence, a state such that energy is transferred from large to small
lengthscales. Here, wave turbulence is observed in experiments on a vibrating
plate. The frequency power spectra of the normal velocity of the plate may be
rescaled on a single curve, with power-law behaviors that are incompatible with
the weak turbulence theory of D{\"u}ring et al. [Phys. Rev. Lett. 97, 025503
(2006)]. Alternative scenarios are suggested to account for this discrepancy --
in particular the occurrence of wave breaking at high frequencies. Finally, the
statistics of velocity increments do not display an intermittent behavior
Nonlinear optical memory effect
Light propagating through random media produces characteristic speckle patterns, directly related to the large multitude of scattering events. These complex dynamics remarkably display robustness to perturbation of the incoming light parameters, maintaining correlation in the scattered wavefront. This behavior is known as the optical memory effect. Here we unveil the properties of the nonlinear optical memory effect, which occurs when an optothermal nonlinearity perturbs the random material. The effect is characterized through a series of pump and probe experiments in silica aerogel, in the visible range. This additional degree of freedom further generalizes the memory effect, opening the road to applications based on the nonlinear response of random media. (C) 2019 Optical Society of Americ
Prediction of the dynamic oscillation threshold in a clarinet model with a linearly increasing blowing pressure
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