High-viscosity Media Research Articles

Characterizations of kinetic power and propulsion of the nematode Caenorhabditis elegans based on a micro-particle image velocimetry system.

Quantifying the motility of micro-organisms is beneficial in understanding their biomechanical properties. This paper presents a simple image-based algorithm to derive the kinetic power and propulsive force of the nematode Caenorhabditis elegans. To avoid unnecessary disturbance, each worm was confined in an aqueous droplet of 0.5 μl. The droplet was sandwiched between two glass slides and sealed with mineral oil to prevent evaporation. For motion visualization, 3-μm fluorescent particles were dispersed in the droplet. Since the droplet formed an isolated environment, the fluid drag and energy loss due to wall frictions were associated with the worm's kinetic power and propulsion. A microparticle image velocimetry system was used to acquire consecutive particle images for fluid analysis. The short-time interval (Δt < 20 ms) between images enabled quasi real-time measurements. A numerical simulation of the flow in a straight channel showed that the relative error of this algorithm was significantly mitigated as the image was divided into small interrogation windows. The time-averaged power and propulsive force of a N2 adult worm over three swimming cycles were estimated to be 5.2 ± 3.1 pW and 1.0 ± 0.8 nN, respectively. In addition, a mutant, KG532 [kin-2(ce179) X], and a wild-type (N2) worm in a viscous medium were investigated. Both cases showed an increase in the kinetic power as compared with the N2 worm in the nematode growth medium due to the hyperactive nature of the kin-2 mutant and the high viscosity medium used. Overall, the technique deals with less sophisticated calculations and is automation possible.

Planarization of 2 ̋ Sapphire Wafer Using Magnetic Abrasive Polishing Process

In this study, the process of magnetic abrasive polishing (MAP), installed permanent magnet to improved magnetic force on surface of wafer, was used for planarization of sapphire wafer. The surface roughness and polished area were investigated according to polishing time. The results showed that the improving strategy of magnetic force was helpful to improvethe roughness of sapphire and the polished area was gradually increased according to polishing time since the frictional heat between magnetic abrasives and wafer surface caused the improvement of fluidity for magnetic abrasive. In addition to, for using medium based on oil, the better improvement of surface roughness was achieved comparing to silicone gel medium of high viscosity.

Rheotaxis Guides Mammalian Sperm

In sea urchins, spermatozoan motility is altered by chemotactic peptides, giving rise to the assumption that mammalian eggs also emit chemotactic agents that guide spermatozoa through the female reproductive tract to the mature oocyte. Mammalian spermatozoa indeed undergo complex adaptations within the female (the process of capacitation) that are initiated by agents ranging from pH to progesterone, but these factors are not necessarily taxic. Currently, chemotaxis, thermotaxis, and rheotaxis have not been definitively established in mammals. Here, we show that positive rheotaxis, the ability of organisms to orient and swim against the flow of surrounding fluid, is a major taxic factor for mouse and human sperm. This flow is generated within 4 hr of sexual stimulation and coitus in female mice; prolactin-triggered oviductal fluid secretion clears the oviduct of debris, lowers viscosity, and generates the stream that guides sperm migration in the oviduct. Rheotaxic movement is demonstrated in capacitated and uncapacitated spermatozoa in low- and high-viscosity media. Finally, we show that a unique sperm motion, which we quantify using the sperm head's rolling rate, reflects sperm rotation that generates essential force for positioning the sperm in the stream. Rotation requires CatSper channels, presumably by enabling Ca(2+) influx. We propose that rheotaxis is a major determinant of sperm guidance over long distances in the mammalian female reproductive tract. Coitus induces fluid flow to guide sperm in the oviduct. Sperm rheotaxis requires rotational motion during CatSper channel-dependent hyperactivated motility.

Advantages Available in the Application of the Semi-Integral Electroanalysis Technique for the Determination of Diffusion Coefficients in the Highly Viscous Ionic Liquid 1-Methyl-3-Octylimidazolium Hexafluorophosphate

While it is common to determine diffusion coefficients from steady-state voltammetric limiting current values, derived from microelectrode/rotating disk electrode measurements or transient peak currents at macroelectrodes, application of these methods is problematic in highly viscous ionic liquids. This study shows that the semi-integral electroanalysis technique is highly advantageous under these circumstances, and it has allowed the diffusion coefficient of cobaltocenium, [Co(Cp)(2)](+) (simple redox process), and iodide, I(-) (complex redox mechanism), to be determined in the highly viscous ionic liquid 1-methyl-3-octylimidazolium hexafluorophosphate (viscosity = 866 cP at 20 °C) from transient voltammograms obtained using a 1.6 mm diameter Pt electrode. In such a viscous medium, a near-steady-state current is not attainable with a 10 μm diameter microdisk electrode or a 3 mm diameter Pt rotating disk electrode, while peak currents at a macrodisk are subject to ohmic drop problems and the analysis is hampered by difficulties in modeling the processes involved in the oxidation of iodide. The diffusion coefficients of [Co(Cp)(2)](+) and I(-) were determined to be 9.4 (±0.3) × 10(-9) cm(2) s(-1) and 7.3 (±0.3) × 10(-9) cm(2) s(-1), respectively. These results highlight the utility of the semi-integral electroanalysis technique for quantifying the diffusivity of electroactive species in high viscosity media, where the use of steady-state techniques and transient peak currents is often limited.

The effect of maximum open height on operating characteristics of polymer injected pump poppet valve

Reciprocating polymer injected pump is the key injection equipment of tertiary oil recovery, the poppet valve in it exists the problem of large vibration noise, low efficiency and short life when transportation high viscosity medium. So the CFD technique is adopted to simulate and analyze the inner flow fields of fluid end poppet valve. According to the practical structure of the poppet valve, a simplified 2D axis-symmetry geometry model of the flow field is established. Combined with pump speed, plunger stroke and plunger diameter, given the boundary condition of the inlet valve, then the numerical simulation of flow field under six different maximum open heights is done depending on software Fluent. The relationship between open height to valve gap flow velocity, hydraulic loss and lag angle is obtained. The results indicate that, with the increase of open height, the valve gap flow velocity decreases, inlet outlet pressure differential decreases and hydraulic loss decreases. But the lag angle is continuously increasing with the increase of maximum open height, the valve has a good work performance when the open height is 1, 1.5, 2, 2.5, 3mm, but when it reaches 3.5mm, the valve performance becomes poor. The study can offer certain reference to understand operating characteristics of poppet valve, help to reduce the hydraulic losses and raise volume efficiency of the pump.

Quantifying rheological and fine particle attachment contributions to coarse particle recovery in flotation

This study focused on the flotation behaviour of very coarse quartz particles in the presence of fine silica and alumina, both of which were used as pulp viscosity modifiers. A decrease in the contact angle of the coarse quartz particles, caused by the attachment of fine particles was believed to be the principal mechanism accounting for the noted depression. Only small surface coverage of attached fine particles may dramatically decrease the quartz particle recovery because the flotation behaviour of the coarse particles was very sensitive to particle hydrophobicity, e.g. less than 5% surface coverage is able to decrease the contact of particles from 83° to 81° and causes a decrease in recovery from 60% to 20%. The effect of removing the fine particles from the pulp, by the process known as desliming, on the flotation behaviour of coarse quartz particles was also investigated. The results showed that desliming is beneficial for the recovery of coarse quartz particles. Furthermore, the recovery of coarse quartz particles attached with fine particles can be restored by conducting flotation in high viscosity medium where glycerol was used as the viscosity modifier.

Detachment of coarse particles from oscillating bubbles—The effect of particle contact angle, shape and medium viscosity

This paper examines the detachment of coarse particles from oscillating bubbles as a function of particle hydrophobicity and shape, as well as medium viscosity. The detachment experiments were conducted using a novel electro-acoustic technique for both ground quartz particles and spherical glass beads of various diameters and hydrophobicity. The detachment force for both types of particles, calculated from the maximum vibration amplitude at which a particle detaches from a bubble, increased with an increase in the contact angle of particles and viscosity of the suspending medium. At low vibration frequencies, the quasi-static model predicts the experimental detachment force reasonably well. In contrast, at high vibration frequency and, particularly, in high viscosity medium, the quasi-static model does not predict the experimental detachment force. It is hypothesised that the magnitude of the detachment force is determined by the dynamic contact angle, which is governed by the velocity of movement of the three phase contact line. Larger detachment forces were observed for the quartz particles compared to that of the spherical glass beads of the same size range and similar contact angle value. The stability of the bubble-particle aggregates at high viscosity has been related to the dynamic contact angle of particles. At high viscosity, the rate of movement of the three phase contact line, which governs the dynamic contact angle, is reduced thus resulting in more stable bubble-particle aggregates.

Improving the recovery of low grade coarse composite particles in porphyry copper ores

The flotation behaviour of low grade, coarse composite particles for two porphyry copper ores was studied. Different grinding times were employed to obtain size distributions for the flotation feed ( d 80) ranging from 150 to 320 μm. Copper containing particles in the fine to intermediate size ranges were recovered in the rougher flotation stage. The rougher tailing was then screened through a 75 μm laboratory sieve. The +75 μm fraction was conditioned with a longer chain collector and floated in either normal viscosity (water) or high viscosity (glycerol–water mixture) medium. The recovery of copper was analysed on an un-sized and size-by-size basis. The recovery of coarse composite copper bearing particles was found to increase in high viscosity medium, even when the liberation of copper bearing minerals was only as low as 10%. The ability to recover these types of particles may result in a reduction in energy consumption in grinding due to the ability to achieve higher overall recovery of valuable mineral at coarse particle size distribution.

Improved Monodispersity of Plasmonic Nanoantennas via Centrifugal Processing

Noble metal nanoparticle clusters underlie a variety of plasmonic devices and measurements including surface-enhanced Raman spectroscopy (SERS). Because of the strong dependence of plasmonic properties on nanoparticle cluster aggregation state, the elimination of non-SERS-active structures and the refinement of the nanoparticle cluster population are critical to realizing uniform and reproducible structures for plasmonic nanoantenna applications such as SERS-based sensors. In this Letter, we report a centrifugal sorting technique for gold core/silica shell nanoparticles that host SERS reporter molecules at the gold/silica interface. The relatively massive nanoparticle clusters are sorted by sedimentation coefficient via centrifugation in a high-viscosity density gradient medium, iodixanol, which yields solutions that contain a preponderance of one aggregation state and a diminished monomer population, as determined by transmission electron microscopy, extinction spectroscopy, and SERS. A quantitative anal...

The influence of viscosity on the functioning of molecular motors

Light driven molecular motors based on sterically overcrowded alkenes achieve repetitive unidirectional rotation through a sequential series of photochemical and thermal steps. The influence of highly viscous environments on the functioning of unidirectional light driven molecular motors is established in the present report using three distinct media. Liquefied propane, a reference medium due to its low viscosity even at 85 K, and two binary solvent systems that undergo a well-defined glass-transition are used to evaluate the influence of glass-like viscosities on both photochemical equilibria and on thermal helix inversion in the molecular motors. It is found that the greater molecular volume of the stable conformations relative to the unstable conformations is responsible for a shift of the photochemical equilibrium from 20% to 100% in favour of the unstable form when irradiated in high viscosity media. These results demonstrate the critical role excluded solvent volume can play in immobilized photo responsive molecular systems. The volume expansion associated with the thermal reversal to the most stable isomer can be used to determine the maximum possible power output of the rotary cycle.

Heat Dissipation Mechanism for Magnetite Nanoparticle in Magnetic Fluid Hyperthermia

We report the results of a study undertaken to determine properties of magnetite particles that disipate heat only through Néel relaxation. The magnetite samples we considered for the heat dissipation studies were found to dissipate heat through both Néel and Brownian relaxations. The relative contributions of both relaxations on magnetic heat dissipation were investigated by analyzing the physical, magnetic, and heating characteristics of magnetite particles with various average diameters dispersed in low and high viscosity media. The results suggested that the size of magnetite particles that dissipated heat through Néel relaxation was around 12 nm and this agreed well with theoretical predictions.

Experimental Study on Revolving Cross-flow Microfiltration of Highly Viscous Liquids

Experimental investigation of the microfiltration (MF) using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylidene fluoride (PVDF, 0.1 μm), cellulose acetate (CA, 0.22 μm), sulfonated polyethersulfone (SPES, 0.22 μm) and polyamide (PA, 0.45 μm), respectively, were used in filtration experiments. The dependence of the filtrate mass of the cross-flow MF on time was measured on-line. The experimental results showed that the effect of the cross-flow on high viscosity medium was more significant than that on the low viscosity one.

Gassed and ungassed power draw in a pilot scale 550 litre fermentor retrofitted with up-pumping hydrofoil B2 impellers in media of different viscosity and with very high power draw

A number of modern impellers have been designed in the pursuit of an alternative to the traditional Rushton turbine, which has a number of well recognized deficiencies. A dual up-pumping combination of the Hayward Tyler B2 (former APV-B2 or simply B2), a high solidity ratio hydrofoil impeller, was retrofitted using traditional methods to a pilot scale fermentor based on cited reference studies of the impeller performance. Using water as a media and comparatively low power draws, the B2 impeller has previously been shown to have good gas handling properties and a low ungassed power number allowing for use at high impeller-to-tank diameter ratio. In the present study a power characterization of the B2 impeller was undertaken in order to extend the available data to viscous media resembling fermentation broths and to very high power draws. Power characterizations were carried out with specific energy input rates up to 12.9 kW/m 3 using different shear-thinning media. The ungassed power number of the B2 impeller was determined (3.3 for power draws in the range 0–11.6 kW/m 3) and our findings confirm those of previous studies and extend the trends to media of high viscosity. Upon aeration the B2 impellers loose little power compared to the traditional impeller even when applying a very high power draw (10–20% power loss at 450 rpm and 1.28 vvm corresponding to 11.6 kW/m 3). Torque fluctuations are found to be small (<5%) for this impeller at high power draw and high viscosity media. Finally it is shown that the B2 impeller can be retrofitted to pilot scale fermentors using traditional methods with a high degree of confidence.

Viscosity model of high-viscosity dispersing system

High-viscosity dispersing system is formed by dispersing the solid particles in the high-viscosity continuous medium. It is very easy to form the three-dimensional network structure for solid particles in the system and the rheology behavior becomes complicated. The apparent viscosity of this dispersing system always has the connection with the volume ratio and the shear rate. In order to discuss the rheology behavior and put up the viscosity model, the suspension of silicon dioxide and silicon oil were prepared. Through testing the viscosity, the solid concentration and the shear rate, the effects of the ratio and the shear rate on viscosity was analyzed, the model of the high-viscosity dispersing system was designed and the model with the printing ink were validated. The experiment results show that the model is applicable to the high-viscosity dispersing systems.

Sterility Testing of a Dispensing Valve for Aseptic Function in Food Service Applications

Manual dispensing equipment for aseptically packaged beverages or foods requires refrigeration of the product package following breakage of the hermetic seal. The food service industry would benefit greatly by implementing dispensing equipment that maintains the sterility of products after continued use without the need for refrigeration. The purpose of this study was to evaluate the ability of a valve, designed to operate aseptically and dispense products with or without refrigeration, to maintain the sterility of products following breakage of the hermetic seal and continued use simulating that of food service. Plastic packages equipped with the “aseptic” dispensing valve in a bag-in-box (BIB) format were aseptically filled with enrichment media with and without the addition of 1% cornstarch to simulate high- and low-viscosity products, respectively. BIBs filled with media were left uninoculated or inoculated (104 CFU/ml) with Staphylococcus aureus or Aspergillus niger on the interior of the spout 1 cm from the opening to simulate consumer misuse. Uninoculated and inoculated BIBs were stored at 25°C, and media were dispensed once to twice per day, every day for up to 30 days to simulate food service use. Dispensates were observed for turbidity (compared with controls) indicating growth in BIBs and, thus, breach of sterility. Growth of samples taken aseptically through the package wall was checked microbiologically every 5 days by standard plating techniques. There was no breach in sterility until day 25. At day 25, uninoculated BIB (1 of 45 samples positive for growth) containing high-viscosity media and BIB inoculated with S. aureus (1 of 45 samples positive for growth) containing lowviscosity media became turbid. Viscosity and type of organism did not appear to influence the ability of the valve to maintain the sterility for ≥20 days. The results of this study provide evidence that the dispensing valve tested can maintain the sterility of aseptically filled products following initial dispensation and continued use under unrefrigerated conditions.

Hydroxypropylmethylcellulose and Methylcellulose Consumption Reduce Postprandial Insulinemia in Overweight and Obese Men and Women ,

Hydroxypropylmethylcellulose (HPMC) and methylcellulose (MC) are modified cellulose dietary fibers that generate viscous solutions in the gastrointestinal (GI) tract. This study assessed the effects of high viscosity (HV) HPMC, ultra-HV (UHV) HPMC, and medium viscosity MC on postprandial glucose and insulin responses in overweight and obese men and women (n = 50). After overnight fasts, subjects consumed 5 breakfast meals containing 75 g carbohydrate, each of which contained 1 of the following: 1 g HV-HPMC, 2 g HV-HPMC, 2 g UHV-HPMC, 4 g medium-viscosity MC or control (2 g cellulose). Test sequence was randomized and double-blind, except the MC test, which was last and single-blind (46 subjects completed all 5 tests). Glucose and insulin responses were determined pre-meal and for 120 min postprandially. Median (interquartile limits) peak glucose concentration was lower (P = 0.001) after the meal containing 2.0 g UHV-HPMC (7.1, 6.3–8.2 mmol/L) compared with the control meal (7.7, 6.6–8.7 mmol/L). The control did not differ from the other conditions for peak glucose or for any of the HPMC/MC conditions for glucose incremental areas under the curves (IAUC). Peak insulin was reduced (P < 0.05) for all HPMC/MC conditions compared with control. Insulin IAUC was lower than control (P < 0.001) after meals containing 2 g HV-HPMC, 2 g UHV-HPMC, and 4 g MC. GI symptoms did not differ among treatments. These findings indicate that HV-HPMC (1 and 2 g), UHV-HPMC (2 g), and MC (4 g) consumption reduced postprandial insulin excursions consistent with delayed glucose absorption.

Impact of mixed-linkage (1→3, 1→4) β-glucans on physical properties of acid-set skim milk gels

The effects of concentration and molecular structure of barley β-glucans on physical properties of skim milk gels acidified at 42 °C by glucono-δ-lactone (GDL) and reaching a final pH of 4.8 were investigated. Incorporation of β-glucans (0.5–2.0%, w/w) into skim milk aqueous dispersions (10%, 12% and 14%, w/w) resulted in weakening of the protein network upon acidification as shown by reduction of the storage modulus ( G′) values of the composite gels, compared with control (free of β-glucan) formulations. However, dynamic rheometry and large deformation measurements (texture profile analysis) revealed that this weakening effect could be reduced or eliminated by using β-glucans with certain molecular features that either promote development of a high viscosity medium (high molecular weight) or formation of a secondary gel network structure (low molecular weight and/or high trimer/tetramer ratio) by the polysaccharide itself. Despite the fact that inclusion of β-glucans at low concentrations increased the levels of spontaneous syneresis, using high β-glucan concentrations or polysaccharide preparations with the aforementioned structural characteristics resulted in milk gels with significantly lower serum separation compared to control formulations.

SadC reciprocally influences biofilm formation and swarming motility via modulation of exopolysaccharide production and flagellar function.

Pseudomonas aeruginosa has served as an important organism in the study of biofilm formation; however, we still lack an understanding of the mechanisms by which this microbe transitions to a surface lifestyle. A recent study of the early stages of biofilm formation implicated the control of flagellar reversals and production of an exopolysaccharide (EPS) as factors in the establishment of a stable association with the substratum and swarming motility. Here we present evidence that SadC (PA4332), an inner membrane-localized diguanylate cyclase, plays a role in controlling these cellular functions. Deletion of the sadC gene results in a strain that is defective in biofilm formation and a hyperswarmer, while multicopy expression of this gene promotes sessility. A DeltasadC mutant was additionally found to be deficient in EPS production and display altered reversal behavior while swimming in high-viscosity medium, two behaviors proposed to influence biofilm formation and swarming motility. Epistasis analysis suggests that the sadC gene is part of a genetic pathway that allows for the concomitant regulation of these aspects of P. aeruginosa surface behavior. We propose that SadC and the phosphodiesterase BifA (S. L. Kuchma et al., J. Bacteriol. 189:8165-8178, 2007), via modulating levels of the signaling molecule cyclic-di-GMP, coregulate swarming motility and biofilm formation as P. aeruginosa transitions from a planktonic to a surface-associated lifestyle.

The rheologic properties of erythrocytes: a study using an automated rheoscope

Red blood cells (RBCs) suspended in a high-viscosity medium were filmed while flowing through a microchannel using an automated rheoscope. Under these conditions, erythrocytes take different orientations and undergo varying deformation according to their location in the velocity profile. Measurements of the mean deformation at several distances from the center of the microchannel at a constant flow rate were acquired for normal and thalassemia erythrocytes. The measurements demonstrate how diagnosis can be made based on a single flow rate in contrast to conventional methods where shear is mechanically controlled. The spatial distribution and velocity of RBCs and rigid microspheres (1 μm) were measured. The maximum slip velocity was found to be linearly correlated to the flow rate for both cells and microspheres. RBCs showed enhanced inward lateral migration compared to the rigid spheres, which is attributed to RBC deformation. The results demonstrate the coupling between RBC mechanical properties and their motion in microvessels.

Correlation between erythrocytes deformability and size: A study using a microchannel based cell analyzer

The deformability of erythrocytes is of great importance for oxygen delivery in the microcirculation [ Lipowsky, H.H., 2005. Microvascular rheology and hemodynamics. Microcirculation 12, 5–15]. Aging of erythrocytes is associated with a reduction in deformability and also in size. The present work describes an automated cell analyzer which utilizes a glass microchannel and advanced image processing software. Erythrocytes suspended in a high viscosity medium are filmed flowing through the microchannel. Under these conditions, the cells assume different orientations and undergo varying deformations according to their location in the velocity profile. The cell analyzer enables the measurement of individual erythrocyte velocity, deformability and volume at varying depths within the microchannel. The volume of the cells is calculated based on the experimental data and a fluid mechanics model. The results obtained show that, on average, the deformability of the cells increases with increase in their size. Additionally, the behavior of RBCs in a microchannel is investigated, showing promising diagnostic possibilities.