Evolution and features of dust devil-like vortices in turbulent Rayleigh-Bénard convection - an experimental study. - In: JGR, ISSN 2169-8996, Bd. 128 (2023), 2, e2022JD037466, S. 1-20
We present an experimental study simulating atmospheric dust devils in a controlled laboratory experiment. The experimental facility, called the “Barrel of Ilmenau” (www.ilmenauer-fass.de) represents a classical Rayleigh-Bénard set-up and is believed to model the phenomena in a convective atmospheric boundary layer fairly well. Our work complements and extends the numerical work of Giersch and Raasch (2021) https//doi.org/10.1029/2020jd034334 by experiments. Dust devils are thermal convective vortices with a vertical axis of rotation visualized by entrained soil particles. They evolve in the convective atmospheric boundary layer and are believed to substantially contribute to the aerosol transport into the atmosphere. Thus, their evolution, size, lifetime, and frequency of occurrence are of particular research interest. Extensive experimental studies have been conducted by field measurements and laboratory experiments so far. Beyond that, our study is the first attempt of Rayleigh-Bénard convection (RBC) in air to investigate dust devil-like vortices in a laboratory experiment. Up to now, this set-up mimics the natural process of dust devil evolution as closest to reality. The flow measurement was carried out by particle tracking velocimetry using neutrally buoyant soap bubbles. We initially identified dust devil-like vortices by eye from the Lagrangian velocity field, and in a later, more sophisticated analysis by a specific algorithm from the corresponding Eulerian velocity field. We analyzed their frequency of occurrence, observation time, and size. With our work, we could demonstrate that turbulent RBC is an appropriate model to mimic the natural process of the evolution of dust devils in the convective atmospheric boundary layer without artificial stimulation.
https://doi.org/10.1029/2022JD037466
Particle detection and size recognition based on defocused particle images: a comparison of a deterministic algorithm and a deep neural network. - In: Experiments in fluids, ISSN 1432-1114, Bd. 64 (2023), 2, 21, S. 1-16
The systematic manipulation of components of multimodal particle solutions is a key for the design of modern industrial products and pharmaceuticals with highly customized properties. In order to optimize innovative particle separation devices on microfluidic scales, a particle size recognition with simultaneous volumetric position determination is essential. In the present study, the astigmatism particle tracking velocimetry is extended by a deterministic algorithm and a deep neural network (DNN) to include size classification of particles of multimodal size distribution. Without any adaptation of the existing measurement setup, a reliable classification of bimodal particle solutions in the size range of 1.14 μm–5.03 μm is demonstrated with a precision of up to 99.9 %. Concurrently, the high detection rate of the particles, suspended in a laminar fluid flow, is quantified by a recall of 99.0 %. By extracting particle images from the experimentally acquired images and placing them on a synthetic background, semi-synthetic images with consistent ground truth are generated. These contain labeled overlapping particle images that are correctly detected and classified by the DNN. The study is complemented by employing the presented algorithms for simultaneous size recognition of up to four particle species with a particle diameter in between 1.14 μm and 5.03 μm. With the very high precision of up to 99.3 % at a recall of 94.8 %, the applicability to classify multimodal particle mixtures even in dense solutions is confirmed. The present contribution thus paves the way for quantitative evaluation of microfluidic separation and mixing processes.
https://doi.org/10.1007/s00348-023-03574-2
Effect of poly-crystallinity on the magnetoelectric behavior of TiN/AlN/Ni MEMS cantilevers investigated by finite element methods. - In: Physica status solidi, ISSN 1862-6319, Bd. 220 (2023), 16, 2200839, S. 1-6
Herein, magnetoelectric microelectromechanical system (MEMS) cantilevers are investigated on basis of a TiN/AlN/Ni laminate derived from experimental sensors using finite-element simulations. With the anisotropic ΔE effect as an implication of the magnetocrystalline anisotropy, the lateral sensitivity of the sensor is studied for different nickel layer thicknesses and boundary conditions. It is found that above 60% of the cantilever length, the nickel is effectively not contributing to the sensor sensitivity anymore which is supported by the investigation of sensors with partial nickel coverage. The boundary condition of the magnetostrictive layer is found to affect the sensitivity of thick layers while it is negligible for thinning layers. Further investigations on basis of polycrystalline untextured nickel with slightly preferred orientations reveal a stronger effect on thin layers than on thicker ones. It is found to arise from relatively large crystals in the high-sensitivity region near the clamping of the sensor. For thicker polycrystalline layers, the ΔE effect reproduces a characteristic based mainly on the (110) and (111) orientations while the (100) orientation appears to be underrepresented.
https://doi.org/10.1002/pssa.202200839
C60 fullerene attenuates muscle force reduction in a rat during fatigue development. - In: Heliyon, ISSN 2405-8440, Bd. 8 (2022), 12, e12449, S. 1-9
C60 fullerene (C60) as a nanocarbon particle, compatible with biological structures, capable of penetrating through cell membranes and effectively scavenging free radicals, is widely used in biomedicine. A protective effect of C60 on the biomechanics of fast (m. gastrocnemius) and slow (m. soleus) muscle contraction in rats and the pro- and antioxidant balance of muscle tissue during the development of muscle fatigue was studied compared to the same effect of the known antioxidant N-acetylcysteine (NAC). C60 and NAC were administered intraperitoneally at doses of 1 and 150 mg kg−1, respectively, daily for 5 days and 1 h before the start of the experiment. The following quantitative markers of muscle fatigue were used: the force of muscle contraction, the level of accumulation of secondary products of lipid peroxidation (TBARS) and the oxygen metabolite H2O2, the activity of first-line antioxidant defense enzymes (superoxide dismutase (SOD) and catalase (CAT)), and the condition of the glutathione system (reduced glutathione (GSH) content and the activity of the glutathione peroxidase (GPx) enzyme). The analysis of the muscle contraction force dynamics in rats against the background of induced muscle fatigue showed, that the effect of C60, 1 h after drug administration, was (15-17)% more effective on fast muscles than on slow muscles. A further slight increase in the effect of C60 was revealed after 2 h of drug injection, (7-9)% in the case of m. gastrocnemius and (5-6)% in the case of m. soleus. An increase in the effect of using C60 occurred within 4 days (the difference between 4 and 5 days did not exceed (3-5)%) and exceeded the effect of NAC by (32-34)%. The analysis of biochemical parameters in rat muscle tissues showed that long-term application of C60 contributed to their decrease by (10-30)% and (5-20)% in fast and slow muscles, respectively, on the 5th day of the experiment. At the same time, the protective effect of C60 was higher compared to NAC by (28-44)%. The obtained results indicate the prospect of using C60 as a potential protective nano agent to improve the efficiency of skeletal muscle function by modifying the reactive oxygen species-dependent mechanisms that play an important role in the processes of muscle fatigue development.
https://doi.org/10.1016/j.heliyon.2022.e12449