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In this paper, the inviscid limit of Cauchy’s problem of incompressible micropolar system in three dimensions is considered. As various viscosity coefficients go to zero (i.e., ρ → 0,v → 0,μ → 0 and η → 0), we prove that the solution converges to a solution that the original equations with zero coefficients of the viscosity.

Liquid viscosity is a vital metric in numerous biochemical applications. A precise bio-assay often needs to determine viscosity prior to processing. This article presents a simple viscosity measurement technique based on the [mu]PIV diffusometry. Assessing Brownian motion of neutrally buoyant particles in a micro-sized chamber provides a fast link to the liquid viscosity. The ensemble cross-correlation algorithm was used to extract the viscosity information out of a series of particle images. The width of a correlation peak decreased with the increased viscosity. For an accurate measurement, the study also evaluated deviations resulting from hindered diffusion. A correction factor was obtained by comparing the measured viscosity of glycerol solutions with the reference data. A calibration curve was made to fix the shifted measurements. The advantages of this technique are as follows: small volume (<1 [mu]L), noninvasiveness, ease of use, and low cost. The good agreement between the data measured from the [mu]PIV system and a commercial viscometer validated the approach. To prove the effectiveness, the technique was used to study the viscosity change of dextran solutions and its effect on the kinematics of the micro-swimmer, Caenorhabditis elegans. A broad range of viscosity measurements (>10^sup 3^ mPa s) were achieved. The demonstration confirms the possible use of the technique in other biological applications that requires broad-range and small-volume measurement capabilities for viscosity.[PUBLICATION ABSTRACT]

The effect of variable viscosity on the onset of penetrative convection simulated via internal heating in a fluid layer. The upper surface of a fluid layer is assumed to be deformably free and dependence of viscosity is assumed to be exponential. The resulting eigen value problem is solved using a regular perturbation technique with wave number a as a perturbation parameter. The viscosity parameter, surface deformation and the presence of internal heat source play a decisive role on the stability characteristics of the system.

Cilia/flagella are whip-like, cellular appendages, widely conserved across the eukaryotes, that move a single cell through fluid, or move fluid across epithelial tissue. The flagella in the biflagellate alga Chlamydomonas reinhardtii are homologous to those found in humans, for example in sperm cells, and therefore, studying flagella in the algae can shed light on human disease. In this thesis, I develop a new quantitative framework for characterising flagellar activity, beginning by tracking the waveforms of C. reinhardtii flagella, and using the tracked waveforms to estimate various parameters that are relevant to flagellar beating, including frequency, amplitude, synchrony, hydrodynamic and elastic moments, curvature propagation and beat variability. These parameters have been estimated for wild-type and outer-dynein mutant flagella, as well as those immersed in a higher-viscosity medium, and for actively regrowing flagella. The results show that flagella of the mutant strain propagate weaker beats than in the wild type, while those in a raised viscosity are weaker still. For example, in a novel measure of the strength of curvature propagation, the mutant is 38% weaker, and the high-viscosity flagella 80% weaker, than the wild type. Additionally, the dynein mutant shows increased variability of the centre of force, but not the beat frequency. These results could aid with diagnosis of diseases caused by defective cilia, such as primary ciliary dyskinesia, as well as gaining further insight into the mechanisms of diseases caused by excessively viscous mucus, such as cystic fibrosis. Regrowing flagella were found to gradually recover their full-length parameters, but this increase in length was accompanied by an increase in the noise with which they beat, and a temporary aberration in the other flagellum.

Measuring the viscosity of the melt contributes to the quality of injection molded products. Injection molding machines cannot give much feedback on the processes in the cavity, so pressure measurement inside the mold facilitates quality supervision. Our goal is to get more information about the viscosity of the material during filling in a traditional injection mold. A suitable and cost-effective method is to install cavity pressure sensors for the in-situ viscosity measurement. We prepared an experimental mold with variable wall thickness and 80×80 mm cavity dimensions. We implemented eight pressure sensors in each cavity. The wall thickness varied from 1 to 4 mm, and apparent viscosity was determined at different shear rates and mold temperatures. We measured non-isothermal and non-adiabatic flow during filling. The environment was quite different from that of standard measuring equipment. Based on the results, we effectively measured the material viscosity with a non-heated mold in the case of acrylonitrile-butadiene-styrene (ABS) and polypropylene (PP) material. The results were validated by measuring viscosity with a capillary rheometer and compared to our method using the non-heated mold, and the error was less than 10%. The results were accurate in a specific speed wall thickness range with PP and ABS.

The miscibility of starch and poly(ethyleneglycol) (PEG)blends in water were investigated by viscosity, densityand refractive index studies. The physical interactionparameters like poly-solvent and blend-solvent have beencalculated using viscosity and density data. Starch/PEGblends were found to be miscible in all studied ratios. Thestudy also revealed that variation of temperature does notaffect the miscibility of starch and PEG blends in theaqueous solution significantly. The miscibility occurs dueto presence of hydroxyl-hydroxyl interactions in theblends. The result obtained reveals that PEG can beeffectively used as gelating agent in starch solution.Keywords: Miscibility, viscosity, polymer interaction, starch, PEG

Our study is centered around a pivotal question: How does the increase in adipose tissue, which defines obesity, impact hemorheological parameters? By delving into this question, we aim to underscore the crucial role of fat tissue increase in obesity, a topic of significant interest and importance in the field of physiology and obesity research. Individuals with a body mass index (BMI) of 25 and above were included in this study. Height was measured with bare feet on flat surface, then, using the bioimpedance device (Tanita-BC418), weight, BMI, fat percentage, fat mass (FM), and fat-free mass were determined. Using the Brookfield viscometer, several shear rates were utilized (for whole blood, 75, 150, 300, and 450 sec–1; for plasma 450 sec–1) in accordance with established standards and test procedures. Whole blood and plasma viscosity were studied in Hamidiye Medical Faculty Hemorheology laboratory. Plasma viscosity in the obese group was significantly (P = 0.01) higher than in the non-obese group, and increased statistically in proportion to weight, BMI, FM, fat-free mass (P < 0.05) in the obese group. At shear rates of 300 and 450 sec–1 (P < 0.05) were determined statistically significant differences between the obese and nonobese groups in whole blood viscosity (WBV). In the obese group, WBV at a shear rate of 75, 150, 300, and 450 sec–1 showed a positive correlation with weight, BMI, FM (P < 0.05). Increased adipose tissue significantly affect plasma and blood viscosities in obesity. The increase in plasma and WBV is directly associated with the increase in adipose tissue. •The obese group had significantly higher values compared to the non-obese group in age, height, weight, BMI, fat percentage, fat mass, and fat-free mass (P < 0.001).•At lower shear rates (75 and 150 sec–¹), WBV was higher in the obese group but did not reach statistical significance.•At higher shear rates (300 and 450 sec–¹), WBV was significantly higher in the obese group.•Plasma viscosity at a shear rate of 450 sec–¹ was significantly higher in the obese group compared to the non-obese group.•WBV at all shear rates was strongly positively correlated with height, weight, BMI, fat mass, and fat-free mass (P < 0.05) in obese group.•Obesity-related parameters (BMI, fat mass, and fat-free mass) strongly influence WBV and PV in the obese group, whereas these correlations are absent in the non-obese group.

This article focuses on the potential of biochar as a treatment for used engine oil, specifically examining its impact on oil viscosity. Used engine oil poses significant environmental risks due to its toxic components. Biochar, a carbon-rich material with high surface area and versatile surface chemistry, has shown promise in various environmental remediation applications. The study investigates how biochar interacts with used engine oil, particularly in altering its viscosity by adsorbing contaminants and improving oil-water separation. By exploring the physicochemical properties of biochar and its potential to support bioremediation and catalysis, this review highlights its role in modifying the viscosity of used engine oil. The findings suggest that biochar may offer a sustainable and effective solution for improving oil properties, thereby providing environmental and economic benefits. Further experimental studies are needed to validate these findings and optimize biochar-based treatments for real-world applications.