117 research outputs found
FCC/HCP Martensitic Transformation and High-Temperature Shape Memory Properties in Co-Si Alloys
Axial and nonaxial migration of red blood cells in a microtube
Human red blood cells (RBCs) are subjected to high viscous shear stress, especially during microcirculation, resulting in stable deformed shapes such as parachute or slipper shape. Those unique deformed RBC shapes, accompanied with axial or nonaxial migration, cannot be fully described according to traditional knowledge about lateral movement of deformable spherical particles. Although several experimental and numerical studies have investigated RBC behavior in microchannels with similar diameters as RBCs, the detailed mechanical characteristics of RBC lateral movement—in particular, regarding the relationship between stable deformed shapes, equilibrium radial RBC position, and membrane load—has not yet been fully described. Thus, we numerically investigated the behavior of single RBCs with radii of 4 µm in a circular microchannel with diameters of 15 µm. Flow was assumed to be almost inertialess. The problem was characterized by the capillary number, which is the ratio between fluid viscous force and membrane elastic force. The power (or energy dissipation) associated with membrane deformations was introduced to quantify the state of membrane loads. Simulations were performed with different capillary numbers, viscosity ratios of the internal to external fluids of RBCs, and initial RBC centroid positions. Our numerical results demonstrated that axial or nonaxial migration of RBC depended on the stable deformed RBC shapes, and the equilibrium radial position of the RBC centroid correlated well with energy expenditure associated with membrane deformations.Takeishi N, Yamashita H, Omori T, Yokoyama N, Sugihara-Seki M. Axial and Nonaxial Migration of Red Blood Cells in a Microtube. Micromachines. 2021; 12(10):1162. https://doi.org/10.3390/mi1210116
Effect of Alloying Elements on fcc/hcp Martensitic Transformation and Shape Memory Properties in Co-Al Alloys
Morphological asymmetries of quasar host galaxies with Subaru Hyper Suprime-Cam
How does the host galaxy morphology influence a central quasar or vice versa?
We address this question by measuring the asymmetries of 2424 SDSS quasar hosts
at using broad-band () images from the Hyper Suprime-Cam
Subaru Strategic Program. Control galaxies (without quasars) are selected by
matching the redshifts and stellar masses of the quasar hosts. A two-step
pipeline is run to decompose the PSF and \sersic\ components, and then measure
asymmetry indices (, , and ) of each
quasar host and control galaxy. We find a mild correlation between host
asymmetry and AGN bolometric luminosity () for the full sample
(spearman correlation of 0.37) while a stronger trend is evident at the highest
luminosities (). This then manifests itself into quasar hosts
being more asymmetric, on average, when they harbor a more massive and highly
accreting black hole. The merger fraction also positively correlates with
and reaches up to 35\% for the most luminous. Compared to control
galaxies, quasar hosts are marginally more asymmetric (excess of 0.017 in
median at 9.4 level) and the merger fractions are similar (). We quantify the dependence of asymmetry on optical band which
demonstrates that mergers are more likely to be identified with the bluer bands
and the correlation between and asymmetry is also stronger in
such bands. We stress that the band dependence, indicative of a changing
stellar population, is an important factor in considering the influence of
mergers on AGN activity.Comment: 27 pages, 28 figure
Swimming of Spermatozoa in a Maxwell Fluid
It has been suggested that the swimming mechanism used by spermatozoa could be adopted for self-propelled micro-robots in small environments and potentially applied to biomedical engineering. Mammalian sperm cells must swim through a viscoelastic mucus layer to find the egg cell. Thus, understanding how sperm cells swim through viscoelastic liquids is significant not only for physiology, but also for the design of micro-robots. In this paper, we developed a numerical model of a sperm cell in a linear Maxwell fluid based on the boundary element slender-body theory coupling method. The viscoelastic properties were characterized by the Deborah number (De), and we found that, under the prescribed waveform, the swimming speed decayed with the Deborah number in the small-De regime (De < 1.0). The swimming efficiency was independent of the Deborah number, and the decrease in the swimming speed was not significantly affected by the wave pattern
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