Solutions Of Different Viscosities Research Articles

A Machine Learning Approach to Predict Fluid Viscosity Based on Droplet Dynamics Features

In recent years, machine learning has made significant progress in the field of micro-fluids, and viscosity prediction has become one of the hotspots of research. Due to the specificity of the application direction, the input datasets required for machine learning models are diverse, which limits the generalisation ability of the models. This paper starts by analysing the most obvious kinetic feature induced by viscosity during flow—the variation in droplet neck contraction with time (hmin/R∼τ). The kinetic processes of aqueous glycerol solutions of different viscosities when dropped in air were investigated by high-speed camera experiments, and the kinetic characteristics of the contraction of the liquid neck during droplet falling were extracted, using the Ohnesorge number (Oh=μ/(ρRσ)1/2) to represent the change in viscosity. Subsequently, the liquid neck contraction data were used as the original dataset, and three models, namely, random forest, multiple linear regression, and neural network, were used for training. The final results showed superior results for all three models, with the multivariate linear regression model having the best predictive ability with a correlation coefficient R2 of 0.98.

Quantification of cell shape, intracellular flows and transport based on DIC object detection and tracking.

Computational image analysis combined with label-free imaging has helped maintain its relevance for cell biology, despite the rapid technical improvements in fluorescence microscopy with the molecular specificity of tags. Here, we discuss some computational tools developed in our lab and their application to quantify cell shape, intracellular organelle movement and bead transport in vitro, using differential interference contrast (DIC) microscopy data as inputs. The focus of these methods is image filtering to enhance image gradients, and combining them with segmentation and single particle tracking (SPT). We demonstrate the application of these methods to Escherichia coli cell length estimation and tracking of densely packed lipid granules in Caenorhabditis elegans one-celled embryos, diffusing beads in solutions of different viscosities and kinesin-driven transport on microtubules. These approaches demonstrate how improvements to low-level image analysis methods can help obtain insights through quantitative cellular and subcellularmicroscopy.

MSC Differentiation: Osteogenic and Adipogenic Differentiation of Mesenchymal Stem Cells in Gelatin Solutions of Different Viscosities (Adv. Healthcare Mater. 23/2020)

MSC Differentiation: Osteogenic and Adipogenic Differentiation of Mesenchymal Stem Cells in Gelatin Solutions of Different Viscosities (Adv. Healthcare Mater. 23/2020)

Periodic open cellular structures (POCS) as enhanced catalyst supports: Optimization of the coating procedure and analysis of mass transport

Aluminum periodic open cellular structures (POCS) of cylindrical shape (9 mm diameter and 4−25 mm length) manufactured by investment casting were investigated as potential enhanced catalyst carriers. Samples with an ideal cubic cell geometry and different cell sizes - namely 1.5, 1.75 and 2.25 mm - were tested. First, coating experiments were performed aiming at understanding the wet coating deposition process: the influence operative spin coating parameters (i.e. spinning speed, time, acceleration) on final coating thickness was studied using glycerol solutions of different viscosity. Based on this preliminary investigation, POCS were activated by depositing a Pd/CeO2 catalyst by slurry coating techniques and tested under mass-transfer limited conditions in CO oxidation, used as a test reaction for gas/solid limited heterogeneous processes. A correlation for mass transfer performances of these structures in function of the Reynolds number is herein presented and used to compare these novel materials against conventional catalyst supports.

Osteogenic and Adipogenic Differentiation of Mesenchymal Stem Cells in Gelatin Solutions of Different Viscosities.

Accumulating evidence indicates that stem cell fate can be regulated by mechanical properties of the extracellular matrix. Most studies have focused onthe influence of matrix elasticity and viscoelasticity on stem cell differentiation. However, how matrix viscosity affects stem cell differentiation has been overlooked. In this study, a biphasic gelatin solution/hydrogel system is used for 3D culture of human bone marrow-derived mesenchymal stem cells (MSCs) to investigate the influence of gelatin solution viscosity on simultaneous osteogenic and adipogenic differentiation at the same culture condition. Gelatin solution promotes cell proliferation, while its promotive effect decreases with the increase of viscosity. The influence of viscosity on osteogenic and adipogenic differentiation of MSCs shows opposite trends. A high-viscosity gelatin solution results in an increase of alkaline phosphatase (ALP) activity, calcium deposition, and expression of osteogenesis-related genes. On the other hand, in a low-viscosity gelatin solution, a lot of lipid vacuoles are formed and adipogenesis-related genes are highly expressed. The results indicate high viscosity is beneficial for osteogenic differentiation, while low viscosity is beneficial for adipogenic differentiation. These findings suggest the importance of matrix viscosity on stem cell differentiation in 3D microenvironments.

Evaluation of Different Quality-Relevant Aspects of Closed System Transfer Devices (CSTDs).

Health care professionals can be exposed to hazardous drugs such as cytostatics during preparation of drugs for administration. Closed sytem transfer devices (CSTDs) were introduced to provide protection for healthcare professional against unintended exposure to hazardous drugs. The interest in CSTDs has significantly increased after USP <800> monograph was issued. The majority of the studies published so far on CSTDs have focused on their "containment" function. However, other important attributes for CSTDs with potential importance for product quality impact are not yet fully evaluated. In the current study, we evaluated four sytems from different suppliers, in combination with different container closure systems (CCS), using solutions of different viscosity and surface tension. The different CSTD / CCS combinations were tested for (a) containment (integrity) using a highly sensitive helium leak test, (b) the force required for mounting the vial adaptor, (c) contribution to visible and subvisible particles as well as (d) the hold-up volume. Results show that the majority of CSTDs may have leaks varying in size, and that some of them generated visible particles due to stopper coring and subvisible particles, both due to silicon oil and particulate contaminations of the Devices. Finally, the holdup volume was up to 1mL depending on the CSTD type, vial size and solution viscosity. These results show that there is a need to evaluate the compatibility of CSTD systems to select the best system for the intended use and that CSTDs may adversely impact product quality and delivered dose.

Manifestation of fluorophore segmental motion in carbon dots in steady-state fluorescence experiments.

The steady state fluorescence anisotropy of carbon dot solutions of different viscosities η and its variation with temperature T has been investigated. The dependence of the anisotropy on T/η is shown to be described by the Perrin equation, which implies that Brownian rotational motion of carbon dots in solution is a basic mechanism of fluorescence depolarization. Peculiarities of the Perrin plot testify that the luminous entity ("fluorophore") responsible for carbon dot fluorescence displays noticeable segmental motions, which are independent of the overall rotational diffusion of the dots. The Perrin model fit to the experimental data yields the effective volumes of the fluorophore VF = 0.35 ± 0.15 nm3 and of the carbon dot as a whole VC = 10.5 ± 1.8 nm3. The rotational motions of the fluorophores are shown to be limited and spectrally dependent. A feasible nature of the fluorophores in question is discussed.

The technique of automated applying of polymer coatings used for repair of tractor parts

Restoration of case parts of machines significantly reduces the cost of their repairing. The present paper proposes a method for restoring case parts using the repair size method. Depending on wear degree, the fitment holes are bored to three repair sizes. The prepared hole is inserted with a new bearing, the outer ring of which is covered with a polymeric coating of the appropriate thickness ensuring the fixity of the joint. As a result of theoretical studies, the model was obtained for the formation of a uniform polymer coating on the outer surface of a rotating cylindrical part. The facility and technological equipment were developed for applying a polymer coating of F-40C elastomer solution onto the outer surface of the rotating bearing. The facility includes screwing lathe 1K62, centering drift pin, bath and magnetic holder MV-V. The holder is designed for mounting a bath filled with polymer solution and its plunging movement when rolling bearings are immersed in polymer solution. The drift pin serves for centering and assembling bearings. The assembled drift pin is inserted into the chuck of the machine rotating the pin when applying polymer coating. The screwing lathe 1K62 is equipped with an INNOVERT frequency converter of H3400A05D5K type, which allows adjusting infinitely the spindle speed from 0 min-1. The paper presents the results of experimental studies on the F-40C elastomer shrinkage, the parameters of the mode of immersing parts into its solution, the dependence of the geometric parameters of the formed polymer coating on the components of application and adhesion modes for polymer coatings based on F-40C elastomer solutions of different viscosity. The acceptable thickness of the polymer coating of elastomer F-40C on the bearing 209, ensuring the non-failure operation of the restored seating with a cyclic radial load of 20 kN is 0.1 mm.

Interfacial dynamics of the “sausage” wave for glycerol-water solution/ionic liquid ([BMIM][PF6]) two-phase flow in a microfluidic flow-focusing junction

The interfacial dynamics of stable and regular “sausage” wave for immiscible fluids without surfactants in a flow-focusing device were investigated experimentally by using a high-speed digital camera. Glycerol-water solutions of different viscosities were used as the core stream, and ionic liquid ([BMIM][PF6]) as the sheathing stream. The formation mechanism of “sausage” wave in a flow-focusing device and the regulation of the characteristic size of “sausage” wave were studied systematically. The effects of the flow rate ratio and the capillary number of the core stream on the characterized size of “sausage” wave were investigated. Moreover, the prediction formulas of the initial length of the “sausage” wave, the wavelength and amplitude of the stable “sausage” wave and the formation frequency of the “sausage” were presented. The research is conducive to a full understanding of the effect of the fluid viscosity on interfacial dynamics in microchannel and accordingly provides valuable reference to manipulate soft matter and to synthesize micro-materials such as micro-fibers.

Changes in the flagellar bundling time account for variations in swimming behavior of flagellated bacteria in viscous media

Although the motility of the flagellated bacteria, Escherichia coli, has been widely studied, the effect of viscosity on swimming speed remains controversial. The swimming mode of wild-type E. coli is often idealized as a run-and-tumble sequence in which periods of swimming at a constant speed are randomly interrupted by a sudden change of direction at a very low speed. Using a tracking microscope, we follow cells for extended periods of time in Newtonian liquids of varying viscosity and find that the swimming behavior of a single cell can exhibit a variety of behaviors, including run and tumble and "slow random walk" in which the cells move at a relatively low speed. Although the characteristic swimming speed varies between individuals and in different polymer solutions, we find that the skewness of the speed distribution is solely a function of viscosity and can be used, in concert with the measured average swimming speed, to determine the effective running speed of each cell. We hypothesize that differences in the swimming behavior observed in solutions of different viscosity are due to changes in the flagellar bundling time, which increases as the viscosity rises, due to the lower rotation rate of the flagellar motor. A numerical simulation and the use of resistive force theory provide support for this hypothesis.

Spin coating deposition on complex geometry substrates: Influence of operative parameters

An industrial spin coater was used to coat complex substrates for catalytic applications. Metallic open cell foams (20, 30 and 40 pores per inch, PPI) were coated for times up to 120s using a range of spinning velocities (from 1000 to 3000rpm). Water/glycerol solutions of different viscosities were used as model liquids to assess the influence of operating parameters on the deposition process. Coating weight (i.e., load) was found to decrease with rotation speed and spinning time, while higher coating loads were measured with an increase of viscosity and geometrical support PPI. Moreover, a process to spin coat acid-free cerium oxide slurries was developed to create a catalyst carrier on the three-dimensional substrates. Excellent control of deposited load and good adhesion performance were obtained.

Influence of polymer additives on turbulence in von Karman swirling flow between two disks. II

We present the experimental studies of the influence of polymer additives on the statistical and scaling properties of the fully developed turbulent regime in a von Karman swirling flow driven either by the smooth or bladed disks using only the global measurements of torque Γ and pressure p fluctuations in water- and water-sugar-based solutions of different viscosities, or elasticity El, and different polymer concentrations ϕ as a function of Re in the same apparatus. There are three highlights achieved and reported in the paper: (i) An observation of turbulent drag reduction (TDR) at both the inertial and viscous flow forcing, in a contradiction to a currently accepted opinion that only the viscous forcing leads to TDR, and the unexpected drastic difference in the transition to the fully developed turbulent and TDR regimes in von Karman swirling flow of water-based polymer solutions depending on the way of the forcing; (ii) a continuous transition to TDR in both the normalized torque drop and the rms pre...

Torque and pressure fluctuations in turbulent von Karman swirling flow between two counter-rotating disks. I

We report the experimental studies of the statistical and scaling properties of the fully developed turbulent regime in von Karman swirling flow between counter-rotating disks with and without blades using the only global measurements of the spatially averaged torque Γ and pressure p fluctuations in water and water-sugar solutions of different viscosities in the same cell geometry. We show that for all fluids under investigation probability distribution functions (PDFs) of the torque fluctuations δΓ/Γrms are Gaussian in both the laminar and turbulent regimes and for the both types of the stirrers. On the contrary, PDFs of the pressure fluctuations change from Gaussian in the laminar regime into the skewed shape with the exponential tails toward low-pressure events for both the entrainment methods. Both the friction coefficient Cf and normalized rms of the pressure fluctuations Cp are independent of Re in the fully developed turbulent regime for all fluids under study and found in a good quantitative agreement with the previous results. We also observe that the internal flow variables such as the normalized torque \documentclass[12pt]{minimal}\begin{document}$\bar{\Gamma }/Vp_{rms}$\end{document}Γ¯/Vprms versus the “internal” Reynolds number Rerms = (prms/ρ)1/2Rρ/η instead of the global variables Cf, Cp versus Re show sharp transition into the well developed turbulent regime. We find that the scaling exponents of the fundamental characteristics based only on Γ and p measurements in the range of fully developed turbulent flow, namely, the integral, Taylor, and Kolmogorov dissipation lengths, as well as the Taylor-based Reynolds number Rλ, are in rather fair agreement with the predictions. We would like to emphasize that scaling of the main turbulent parameters Rλ, λ, ηd obtained via the global variables is a very non-trivial result. It is not obvious that measurements based on the global quantities will provide the predicted scaling relations. The result on such scaling obtained previously strongly disagrees with the scaling predictions. Indeed, both \documentclass[12pt]{minimal}\begin{document}$\bar{\Gamma }$\end{document}Γ¯ and prms are averaged over the cell volume as well as all spatial scales, whereas the swirling flow is neither isotropic nor homogeneous. So the global variables being averaged over all spatial scales get contributions from the scales larger and smaller than those from the inertial range of scales. And finally, the normalized characteristic frequencies fp/frot found in both the torque and pressure frequency power spectra in the fully developed turbulent regime have close values, are independent of Re, and associated with either the rotation or oscillation frequency of the main vortex.

Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: Nitroxide radicals in solution

For nitroxide radicals in solution one can identify three frequency regimes in which (1)H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the (1)H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)] with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for (14)N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to (15)N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)]). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of (1)H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data-(1)H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of (14)N and (15)N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in (1)H resonance frequency, 10 kHz-20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.

Viscosity of aluminum under shock-loading conditions

A reliable data treatment method is critical for viscosity measurements using the disturbance amplitude damping method of shock waves. In this paper the finite difference method is used to obtain the numerical solutions for the disturbance amplitude damping behaviour of the sinusoidal shock front in a flyer-impact experiment. The disturbance amplitude damping curves are used to depict the numerical solutions of viscous flow. By fitting the experimental data to the numerical solutions of different viscosities, we find that the effective shear viscosity coefficients of shocked aluminum at pressures of 42, 78 and 101 GPa are (1500±100) Pa·s, (2800±100) Pa·s and (3500±100) Pa·s respectively. It is clear that the shear viscosity of aluminum increases with an increase in shock pressure, so aluminum does not melt below a shock pressure of 101 GPa. This conclusion is consistent with the sound velocity measurement.

Collapsing bubble induced pumping in a viscous fluid

Abstract An experimental study on the effect of liquid viscosity on the pumping efficacy of a jetting bubble is presented. Solutions of different viscosities are obtained using different concentrations of glycerine in water. To study the pumping effect, a low-voltage electrical spark is used to create a bubble near a fixed horizontal plate with a hole. The bubble oscillates and collapses with a high speed jet towards the plate and pumps fluid through the hole. The bubble dynamics are recorded using a high speed camera. As the viscosity increases, the number of bubble oscillations increases even as the bubble eventually collapses with a jet. At very high viscosities, jet formation is suppressed and the bubble does not break up into smaller bubbles upon collapse. The effect of other parameters affecting pumping such as the distance of the bubble-center from the plate and the radius of the hole in the plate, is also studied. Results show that pumping is most effective below a limiting distance of the bubble-center from the plate, which in turn depends on the viscosity. The estimated volumetric flux due to pumping through the hole also decreases with an increase in viscosity. The effect of viscosity on a free-field bubble is also presented in terms of the increase in the number of oscillations and the variation of bubble radius with time.

Viscosity Effect On The AFM Force Measurement

Atomic force microscopy based techniques have been used in the investigation of protein folding/unfolding in order to study the protein properties at the single molecule level. These experiments are performed in buffer solution, where the AFM cantilever is used to exert and measure the mechanical forces on the protein molecules under study. Due to the motion of the cantilever relative to the liquid, a viscous drag force, which can be significant when the liquid is viscous or the cantilever's speed is high, acts on the cantilever. The irregular shape of the liquid chamber and cantilever, and the special boundary conditions of the fluid make this problem complicated and difficult to solve analytically. We measured the viscous drag forces on different cantilevers for several different cantilever speeds in solutions of different viscosities. The results show that the viscous drag on a cantilever is determined by its geometry, its relative speed, the viscosity of the solution, and the separation between the cantilever and the sample surface. This method will be useful to make corrections to the unfolding force data of proteins as well as that of AFM based force measurements.

Optical imaging and analytical modelling of the dynamic concentration gradient of viscous inlet solutions in a microfabricated network design

The design and operation of a gradient network is particularly critical when mixing solutions of different viscosities, which is common with real samples, especially in life science applications. The dynamic concentration gradient formed from mixing equal inlet flow rates of (0.01–1.5 mol/kg) sucrose solution with deionized water in a network was analytically modelled and experimentally investigated. The generation of a stable profile was highly dependent on both the inlet flow rate and the inlet viscosity ratio of the mixed solutions for each case study. The optimum flow rate per inlet for a stable profile was also determined. The experimental investigations show that optimizing the diffusion rate and providing sufficient mixing are key parameters to validate the analytical model. An inlet viscosity ratio of >1.009:1 (with respect to water inlet) was sufficient to perturb the outlet concentration profile. The linearity of the outlet concentration profile decreased and tended towards a sigmoidal profile with increasing sucrose concentration. Enhanced linearity of the outlet concentration profile, through optimizing the inlet flow rate ratio for each case study was also performed.

Thioflavin T as a Molecular Rotor: Fluorescent Properties of Thioflavin T in Solvents with Different Viscosity

The effect of solvent viscosity on thioflavin T (ThT) fluorescent properties is analyzed to understand the molecular mechanisms of the characteristic increase in ThT fluorescence intensity accompanying its incorporation into the amyloid-like fibrils. To this end, the dependencies of the ThT quantum yield and fluorescence lifetime on temperature and glycerol content in the water-glycerol mixtures are studied. It has been found that fluorescent properties of ThT are typical for the specific class of fluorophores known as molecular rotors. It has been established that the low ThT fluorescence intensity in the solvents with low viscosity is caused by the nonradiative deactivation of the excited state associated with the torsional motion of the ThT benzthiazole and aminobenzene rings relative to each other, which results in the transition of ThT molecule to nonfluorescent twisted internal charge transfer (TICT) state. The rate of this process is determined by the solvent viscosity, whereas the emission does occur from the nonequilibrium locally excited (LE) state. High polarization degree of the ThT fluorescence (P = 0.45) observed for glycerol solutions of different viscosity confirms the nonequilibrium character of the emission from the LE state and testifies that rotational correlation time of the whole molecule is considerably greater than the time required to accomplish transition to the nonfluorescent TICT state. Torsional movements of the ThT fragments take place in the same temporal interval as solvent relaxation, which leads to nonexponential fluorescence decay of the dye in viscous solvents. This photophysical model successfully explains the fluorescent properties of ThT in solvents with different viscosities. The model is confirmed by the results of the quantum-chemical calculations, which showed that energy minimum for the ground state of ThT corresponds to conformation with torsional angle phi = 37 degrees between the benzthiazole and aminobenzene rings and in the excited-state twisted conformation of ThT with phi = 90 degrees has minimal energy. These data support the idea that the reason for the characteristic increase in the ThT fluorescence intensity accompanying its incorporation into the amyloid fibrils is determined by the rigidity of the dye environment, which prevents the rotation of the benzthiazole ring relative to the aminobenzene ring in the excited state.

The effect of viscous loading on brain ependymal cilia

Ependymal cilia line the ventricular system moving cerebral spinal fluid close to the brain surface. They may be exposed to fluid of increasing viscosity in certain pathological conditions such as bacterial meningitis. Our aim was to determine the effect of increasing viscosity on ciliary function. Ciliated ependyma was exposed to solutions of different viscosities (1-60cP) and ciliary function assessed by high-speed digital imaging. The mean (S.D.) ciliary beat frequency (CBF), measured after 30min incubation in Medium 199 at 37 degrees C, was 34.9 (2.9)Hz. Increased viscous loading was followed by a rapid decrease in CBF compared to baseline readings (p<0.001). After 15min of exposure to the increased viscous load, CBF reached a new stable level while the viscous load was maintained. Compared to baseline measurements of CBF, viscous loading of 3.7cP caused a 16%, 10.4cP at 34% and 24cP a 70% decrease in beat frequency. Further viscous loading at levels up to 60cP resulted in no further reduction of ependymal CBF. Solutions of 24 and 40cP had no effect on ciliary amplitude. An increase in viscosity to 60cP caused a significant (30%: p=0.001) decrease in the ciliary beat amplitude.