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2022 ◽  
Vol 934 ◽  
Author(s):  
C.A. Klettner ◽  
F.T. Smith

The Poiseuille flow (centreline velocity $U_c$ ) of a fluid (kinematic viscosity $\nu$ ) past a circular cylinder (radius $R$ ) in a Hele-Shaw cell (height $2h$ ) is traditionally characterised by a Stokes flow ( $\varLambda =(U_cR/\nu )(h/R)^2 \ll 1$ ) through a thin gap ( $\epsilon =h/R \ll 1$ ). In this work we use asymptotic methods and direct numerical simulations to explore the parameter space $\varLambda$ – $\epsilon$ when these conditions are not met. Starting with the Navier–Stokes equations and increasing $\varLambda$ (which corresponds to increasing inertial effects), four successive regimes are identified, namely the linear regime, nonlinear regimes I and II in the boundary layer (the ‘ inner’ region) and a nonlinear regime III in both the inner and outer region. Flow phenomena are studied with extensive comparisons made between reduced calculations, direct numerical simulations and previous analytical work. For $\epsilon =0.01$ , the limiting condition for a steady flow as $\varLambda$ is increased is the instability of the Poiseuille flow. However, for larger $\epsilon$ , this limit is at a much higher $\varLambda$ , resulting in a laminar separation bubble, of size ${O}(h)$ , forming for a certain range of $\epsilon$ at the back of the cylinder, where the azimuthal location was dependent on $\epsilon$ . As $\epsilon$ is increased to approximately 0.5, the secondary flow becomes increasingly confined adjacent to the sidewalls. The results of the analysis and numerical simulations are summarised in a plot of the parameter space $\varLambda$ – $\epsilon$ .


Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6816
Author(s):  
Hiroaki Shinya ◽  
Masataka Nakano ◽  
Noboru Ohtani

The step structure on the (0001¯)C facet of 4H-SiC boules grown by the physical vapor transport growth method with different nitrogen doping concentrations was examined in various scales, using different types of microscopy, such as differential interference contrast optical microscopy (DICM) and atomic force microscopy (AFM). DICM observations unveiled characteristic macroscopic surface features of the facet dependent on the nitrogen doping concentration. AFM observations revealed the existence of step trains of half unit-cell height (0.5 nm) on the facet and found that their separation was undulated with a characteristic wavelength dependent on the nitrogen doping concentration; the higher the nitrogen concentration, the longer was the undulation wavelength of step separation. Based on these results, we discussed the origin and formation mechanism of the separation-undulated step structure observed on the (0001¯)C facet of nitrogen-doped 4H-SiC boules.


2021 ◽  
Vol 11 (21) ◽  
pp. 9898
Author(s):  
Jaime Andres Garcia Diosa ◽  
Alejandro Gonzalez Orive ◽  
Guido Grundmeier ◽  
Ruben Jesus Camargo Amado ◽  
Adrian Keller

Coatings of modified TiO2 nanoparticles (TiO2-m) have been shown to effectively and selectively trap non-adherent cancer cells, with an enormous potential for applications in photodynamic therapy (PDT). Leukemia cells have a remarkable affinity for TiO2-m coatings, adhering to the surface by membrane structures and exhibiting morphologic characteristics of amoeboid locomotion. However, the details of the cell–substrate interaction induced by the TiO2-m coating remain elusive. With the aim to obtain a better understanding of this phenomenon, leukemia cell adhesion to such coatings was characterized by atomic force microscopy (AFM) for short contact times up to 60 min. The cell and membrane morphological parameters mean cell height, contact area, cell volume, and membrane roughness were determined at different contact times. These results reveal cell expansion and contraction phases occurring during the initial stage of adhesion. Subsequently, the leukemic cells reach what appears to be a new resting state, characterized by pinning of the cell membrane by TiO2-m nanoparticle aggregates protruding from the coating surface.


Author(s):  
Maarten Klapwijk ◽  
Thomas Lloyd ◽  
Guilherme Vaz

Abstract A new partially averaged Navier-Stokes (PANS) closure is derived based on the KSKL model. The aim of this new model is to incorporate the desirable features of the KSKL model, compared to the SST model, into the PANS framework. These features include reduced eddy-viscosity levels, a lower dependency on the cell height at the wall, well-defined boundary conditions, and improved iterative convergence. As well as the new model derivation, the paper demonstrates that these desirable features are indeed maintained, for a range of modeled-to-total turbulence kinetic energy ratios (f_k), and even for multiphase flow.


2021 ◽  
Vol 25 (5) ◽  
pp. 534-542
Author(s):  
L. M. Pshennikova

The cultivars of the common lilac (Syringa vulgaris) grown in the south of the Russian Far East are not always winter-hardy and are often damaged by fungal diseases due to a very humid climate. A promising trend in the selective breeding of lilacs in Russia is the creation of new breeding material based on the gene pool of the broadleaf lilac (S. oblata) and its hybrids in order to introduce valuable adaptive traits into cultivars. The present work aimed to identify the traits of leaf anatomy in species and cultivars of Syringa resistant and susceptible to Pseudocercospora lilacis, the causative agent of brown leaf spot disease. The study was carried out on the living collection of the Botanical Garden-Institute, Far Eastern Branch, Russian Academy of Sciences (Vladivostok). The leaf anatomical structure of two Syringa species showing different degrees of resistance to P. lilacis in the monsoon climate of the Far East (resistant S. oblata and weakly resistant S. vulgaris, and also their hybrid cultivars) has been analyzed. The differences between species, subspecies, and cultivars are quantitative: they differ in the number of spongy mesophyll layers, the cell height in the first layer of palisade mesophyll, the cell height in the upper and lower epidermises, and the thickness of both mesophylls. The interspecific hybrids resistant or weakly resistant to P. lilacis (brown leaf spot disease) mainly retain the leaf anatomy structure of the maternal plant. One of the traits determining the resistance of hybrid lilac cultivars is an increased number of spongy mesophyll layers in the leaf blade. The study of leaf anatomy has shown that the four-layered spongy mesophyll leaf parenchyma correlates with the resistance of lilacs from the subsection Euvulgaris to P. lilacis. In S. oblata, this trait is inherited down the maternal line. To establish lilac cultivars resistant to fungal diseases, it is advisable to cross the two species (S. oblata and S. vulgaris) or their cultivars using one of S. oblata subspecies as a maternal plant.


Author(s):  
Chen Yang ◽  
Siqi Wu ◽  
Zezhong Mou ◽  
Quan Zhou ◽  
Zheyu Zhang ◽  
...  

Bladder cancer (BCa) is a common lethal urinary malignancy worldwide. The role of ARHGAP family genes in BCa and its association with immuno-microenvironment remain largely unknown. ARHGAP family expression and immune infiltration in BCa were analyzed by bioinformatics analysis. Then, we investigated cell proliferation, invasion, and migration in vivo and in vitro of the ARHGAP family. Furthermore, atomic force microscopy (AFM) was employed in measuring cellular mechanical properties of BCa cells. The results demonstrated that ARHGAP family genes correlate with a tumor-promoting microenvironment with a lower Th1/Th2 cell ratio, higher DC cell infiltration, higher Treg cell infiltration, and T-cell exhaustion phenotype. Silencing ARHGAP5, ARHGAP17, and ARHGAP24 suppressed BCa cell proliferation, migration, and metastasis. Knocking down of ARHGAPs in T24 cells caused a relatively higher Young’s modulus and lower adhesive force and cell height. Taken together, ARHGAP family genes promote BCa progressing through establishing a tumor-promoting microenvironment and promoting cancer progression.


PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254165
Author(s):  
Moritz Schu ◽  
Emmanuel Terriac ◽  
Marcus Koch ◽  
Stephan Paschke ◽  
Franziska Lautenschläger ◽  
...  

The cellular cortex is an approximately 200-nm-thick actin network that lies just beneath the cell membrane. It is responsible for the mechanical properties of cells, and as such, it is involved in many cellular processes, including cell migration and cellular interactions with the environment. To develop a clear view of this dense structure, high-resolution imaging is essential. As one such technique, electron microscopy, involves complex sample preparation procedures. The final drying of these samples has significant influence on potential artifacts, like cell shrinkage and the formation of artifactual holes in the actin cortex. In this study, we compared the three most used final sample drying procedures: critical-point drying (CPD), CPD with lens tissue (CPD-LT), and hexamethyldisilazane drying. We show that both hexamethyldisilazane and CPD-LT lead to fewer artifactual mesh holes within the actin cortex than CPD. Moreover, CPD-LT leads to significant reduction in cell height compared to hexamethyldisilazane and CPD. We conclude that the final drying procedure should be chosen according to the reduction in cell height, and so CPD-LT, or according to the spatial separation of the single layers of the actin cortex, and so hexamethyldisilazane.


2021 ◽  
Vol 0 (0) ◽  
pp. 0-0
Author(s):  
S. Alekseenko ◽  
S. Karpischenko ◽  
S. Artyushkin ◽  
S. Barashkova ◽  
I. Anikin

Background: The objective of the study is evaluation of ciliary function and mucosal cytology after endoscopic sinus surgery in children with chronic rhinosinusitis (CRS). Methodology: A total of 132 children with CRS who underwent endoscopic sinus surgery, as well as 15 healthy controls were involved in the study. In this follow-up study patients were examined preoperatively, as well as 3, 6, 9, and 12 months after endoscopic sinus surgery. Assessment of ciliary function and sinonasal mucosal cytology was performed using high-speed videomicroscopy. Lund-Kennedy, Lund-Mackay, and sinonasal outcome test 20 (SNOT20) scores were also evaluated. Results: Total SNOT-20, Lund-Mackay, and Lund-Kennedy values significantly decreased after sinus surgery. In contrast, ciliary function and mucosal cytology only tended to improve after 6 months. 9 months after surgery the number of ciliated cells, ciliary beat frequency, cell viability, and ciliary length were significantly higher than preoperatively. The most significant improvement of ciliary function and cell height was observed 12 months after operation, whereas epithelial dystrophy and neutrophil infiltration were significantly reduced. Conclusions: Substantial improvement was observed only in a year after surgery, whereas 0 to 3 months after the surgery ciliary function was severely impaired thus predisposing to recurrent sinusitis or other complications.


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