Measurement of blood viscosity using mass-detecting sensor

A newly designed mass-detecting capillary viscometer is extended to measure the viscosity of whole blood over a range of shear rates without the use of anticoagulants in a clinical setting. In the present study as proof of principle, a single measurement of liquid-mass variation with time replaces the flow rate and pressure drop measurements that are usually required for the operation of a capillary tube viscometer. Using a load cell and capillary, we measured the change of mass flowing through capillary tube with respect to the time, m(t), from which viscosity and shear rate were mathematically calculated. For water and adulterated bloods, excellent agreement was found between the results from the mass-detecting capillary viscometer and those from a commercially available rotating viscometer. Also, the mass-detecting capillary viscometer measured the viscosity of unadulterated whole blood without heparin or EDTA. This new method overcomes the drawbacks of conventional viscometers in the measurement of the whole blood viscosity. First, the mass-detecting capillary viscometer can accurately and consistently measure the unadulterated blood viscosity over a range of shear rates in less than 2 min without any anticoagulants. Second, this design provides simplicity (i.e. ease of operation, no moving parts, and disposable) and low cost.     

A model for estimating the medium properties of Avicel to ethanol conversion

Simultaneous saccharification and fermentation received an increasing level of attention over recent decades, with the primary focus on the development of improved enzyme and organism performance. Little literature is available on the effects of the various fermentation components on the apparent dynamic viscosity of the fermentation broth for use in reactor design and analysis. This work investigates density and settling properties of Avicel PH-101 particles and the effects of base medium composition, yeast concentration and cellulose particles on the apparent dynamic viscosity of the fermentation mixture. Dynamic viscosity measurements were obtained using a rotational viscometer equipped with a DG 26.7 double gap concentric cylinder measuring system. Results indicated that Avicel particles experience a greater drag force compared to similar sized spherical particles and have a measured density of 1,605.7 kg m^?3. The Ostwäld-de Waele formulation was used to describe the dynamic viscosity of the particles due to it shear-thinning nature. Correlation between the predicted particle effects and experimental results deviated with a root mean square error of 8.46 %.     

The settling characteristics and mean settling velocity of granular sludge in upflow anaerobic sludge blanket (UASB)-like reactors

Mean settling velocity of granular sludge in full-scale UASB (upflow anaerobic sludge blanket) and EGSB (expanded granular sludge bed) reactors was evaluated by settling column tests, and a settling velocity model based on the experimental results and available literature data was developed. It is concluded that the settling velocity should be calculated by the Allen formula, because the settling process of the granules is in the category of intermediate flow regime rather than in the laminar flow one. The comparison between calculated and measured values of the settling velocity shows an excellent agreement, with an average relative error of 4.04%. A simple but reliable mathematical method to determine the settling velocity is therefore proposed.     

Effect of secondary flow on biological experiments in the cone-plate viscometer: methods for estimating collision frequency, wall shear stress and inter-particle interactions in non-linear flow.

We present a theoretical analysis of fluid flow and particle interactions in the cone-plate viscometer under conditions typically applied in biological studies. The analysis demonstrates that at higher shear rates, besides linear primary flow in the rotational direction, prominent non-linear secondary flow causes additional fluid circulation in the radial direction. Two parameters, the cone angle and Reynolds number, characterize flow in the viscometer over all ranges of shear rate. Our results indicate that secondary flow causes positional variations in: (i) the velocity gradient, (ii) the direction and magnitude of the wall shear stress at the plate surface, (iii) inter-particle collision frequency, (iv) magnitude and periodicity of normal and shear forces applied during particle-particle interactions, and (v) inter-particle attachment times. Thus, secondary flow may significantly influence cellular aggregation, platelet activation and endothelial cell mechanotransduction measurements. Besides cone-plate viscometers, this analysis methodology can also be extended to other experimental systems with complex non-linear flows.     

Lipid fluidity directly modulates the overall protein rotational mobility of the Ca-ATPase in sarcoplasmic reticulum

We have developed a quantitative and relatively model-independent measure of lipid fluidity using EPR and have applied this method to compare the temperature dependence of lipid hydrocarbon chain fluidity, overall protein rotational mobility, and the calcium-dependent enzymatic activity of the Ca-ATPase in sarcoplasmic reticulum. We define membrane lipid fluidity to be T/eta, where eta is the viscosity of a long chain hydrocarbon reference solvent in which a fatty acid spin label gives the same EPR spectrum (quantitated by the order parameter S) as observed for the same probe in the membrane. This measure is independent of the reference solvent used as long as the spectral line shapes in the membrane and the solvent match precisely, indicating that the same type of anisotropic probe motion occurs in the two systems. We argue that this empirical measurement of fluidity, defined in analogy to the macroscopic fluidity (T/eta) of a bulk solvent, should be more directly related to protein rotational mobility (and thus to protein function) than are more conventional measures of fluidity, such as the rate or amplitude of rotational motion of the lipid hydrocarbon chains themselves. This new definition thus offers a fluidity measure that is more directly relevant to the protein's behavior. The direct relationship between this measure of membrane fluidity and protein rotational mobility is supported by measurements in sarcoplasmic reticulum. The overall rotational motion of the spin-labeled Ca-ATPase protein was measured by saturation-transfer EPR. The Arrhenius activation energy for protein rotational mobility (11-12 kcal/mol/degree) agrees well with the activation energy for lipid fluidity, if defined as in this study, but not if more conventional definitions of lipid fluidity are used. This agreement, which extends over the entire temperature range from 0 to 40 degrees C, suggests that protein mobility depends directly on lipid fluidity in this system, as predicted from hydrodynamic theory. The same activation energy is observed for the calcium-dependent ATPase activity under physiological conditions, suggesting that protein rotational mobility (dependent on lipid fluidity) is involved in the rate-limiting step of active calcium transport.     

A newly designed oscillating viscometer for blood viscosity measurements

A newly designed type of oscillating viscometer is described. The viscometer consists of either a tube or a rod oscillating at a resonance frequency with amplitudes in the micro- and nanometer range. A fluid flowing through the tube or surrounding the rod damps the torsional oscillations. The increase in the damping depends on the viscosity of the fluid and is used to determine viscosity. It was found that viscosity measurements are feasible during blood flow. This new type of viscometer may be useful to the study of biophysical properties of blood at the wall surface during flow and give new insights into blood flow. The device allows direct viscosity measurement on blood directly as it is drawn from the vein through the tube without any anticoagulant.     

Cellulose degradation and monitoring of viscosity decrease in cultures of Cellulomonas uda grown on printed newspaper

The rheological behavior of cultures of Cellulomonas uda with shredded printed newspaper as the carbon source was studied. The initial substrate concentrations ranged from 23 to 60 g/L. The changes in apparent viscosity were followed on-line by applying a commercially available process viscometer and discretely using a rotational viscometer with an anchor impeller. During the time of highest cellulose degradation, the broths exhibited a pseudoplastic behavior which could be explained satisfactorily by the power-law model. At the end of cultivation when cellulose degradation slowed down, the broths became Newtonian in behavior. Endo-1,4-beta-glucanase, 1,4-beta-xylanase, beta-glucosidase, and beta-xylosidase activities were also determined during cultivation as well as cellulose degradation and cell mass production. The beginning of endoglucanase formation and the start of the final viscosity decrease of the bacterial paper pulp suspensions could be correlated.     

The effects of larval abundance, settlement and juvenile mortality on the depth distribution of a colonial ascidian

The colonial ascidian Didemnum candidum (Savigny) is more abundant at shallow depths on floating docks than at greater depths along pilings in Pearl Harbor, Oahu, Hawaii. To compare the effects of selective settlement and postsettlement mortality on adult distribution, I determined if settlement was nonrandom relative to depth, if differences in adult abundance were responsible for the depth distribution of settlement, and if juvenile mortality varied with depth. A plankton pump was used to measure variation in larval abundance with depth. Acrylic settling plates were suspended at different depths and sampled nondestructively to measure settlement intensity and juvenile mortality. Settlement and mortality of the didemnid ascidians Diplosoma listerianum Milne-Edwards and Diplosoma sp. were also measured in the field and compared to that of D. candidum. Settlement of D. candidum was indeed nonrandom over depth. Both planktonic larvae and settled juvenils were more numerous at 0.5 than 3 or m. Settlement intensity on vertical plates was greatest within 1–2 cm of the water surface in the laboratory and within 2–3 cm in the field. Directly adjacent to the floating dock, where adults were equally abundant, settlement on horizontal plates was greater at shallow depths, suggesting directed movement of larvae upward. However, the ratio of settled juveniles to planktonic larvae (number of settlers: number of larvae) did not significantly differ with depth, suggesting that larvae were not more likely to settle at a particular depth. Settlement of the Diplosoma species was also heaviest near the surface. Juvenile mortality was greater at 0.5 than at 3 or 6 m for both D. candidum and the Diplosoma species. Experimental settlement showed that mortality, per se, of D. candidum was independent of depth. Rather, mortality was density-dependent, and the higher mortality near the surface was due to the greater number of larvae settling there. At this location, nonrandom settlement appears to determine the adult distribution of D. candidum, despite greater juvenile mortality at shallow depths. The pattern of settlement over depth is largely determined by adult proximity, rather than active larval behavior.     

Oscillating viscometer--evaluation of a new bedside test

A viscometer for bedside blood measurements was developed, consisting of an oscillating resonator probe mounted directly into a disposable vacutainer tube for blood withdrawal. It was tested in vitro on blood samples with variable hematocrits (20-60%), increasing fibrinogen concentrations (0-20 g/l), increasing concentrations of an admixed radiographic contrast medium and erythrocyte suspensions in dextran 40 and dextran 70. Results were compared with those obtained with a conventional Couette viscometer. Oscillating viscometry yielded generally higher values than Couette viscometry, and had a good sensitivity for changes in hematocrit with a good correlation between the two methods (r=0.96, p<0.0001). Oscillating viscosity depended on the resonator frequency, it was higher at 3900 Hz than at 215 Hz, suggesting a viscoelastic behavior of blood. Erythrocyte aggregation, induced by increasing fibrinogen concentrations or dextran 70, affected oscillating viscometry. At a high frequency, i.e. a smaller penetration depth of the shear wave, oscillating viscosity tended to decrease, which suggests a depletion of the boundary layer from erythrocytes when they aggregate. At low frequency with a deeper shear wave penetration (about 50 microm), erythrocyte aggregation increased oscillating viscosity. Bedside tests in 17 patients with coronary heart disease and 10 controls confirmed the easy practicability of the test and showed lower oscillating viscosity in these patients despite higher fibrinogen concentrations presumably due to increased erythrocyte aggregation. We conclude that oscillating viscometry is an interesting bedside test, which is capable of providing new information on the biorheology of the erythrocyte-poor boundary layer near the vessel wall.     

Effect of covering pig slurry stores on the ammonia emission processes

The aim of this study was to evaluate the effects of different covers (oil, plastic film, perforated polystyrene float, peat and zeolites) on slurry settling characteristics and ammonia emission during storage and following surface application in the field. Laboratory trials were carried out for 15 days using a pilot scale device. Samples of 5 kg slurry were used. At the end of the storage period, distributions of dry matter, pH, total ammoniacal nitrogen and total Kjeldahl nitrogen in slurry were characterized. In the field, ammonia volatilisation was measured for three days using a wind tunnel system. Oil and plastic film retained all ammoniacal nitrogen forms in the slurry, whereas the others reduced ammonia volatilisation by reducing the emitting surface or by adsorbing/absorbing ammonia. Over the whole process studied (storage plus application) ammonia emissions were reduced by 40% by oil up to 65-71% by zeolites with different particle sizes.     

Physical properties of liquid nematode cultures and the design of recovery operations

Production of nematode-based pesticides involves the recovery of a viable nematode life stage known as the infective juvenile (IJ) from fermentation broth. In this paper we report the physical properties of mature liquid nematode cultures of P. hermaphrodita, S. feltiae and H. megidis. Properties determined were composition, IJ `shear' sensitivity, viscosity, particle size and component density. These measurements were then used to identify potential recovery procedures. Waste components in cultures included non-IJ life stages, dead nematodes, nematode debris, spent media and the nematodes' associated bacteria. Infective juveniles were very sensitive to `shear' compared to baker's yeast. The choice of recovery equipment will therefore be limited to that which produces a low level of stress. Comparison of IJ properties with those of waste components showed that differences in component size, density and settling rate can be used as a basis for separating fermentation waste. Predictions of IJ settling velocity using Stokes' Law and by experiment confirmed that IJs will need to be separated from culture liquid by centrifugation as opposed to gravity settling. The comparison of nematodes revealed a dependence of culture properties on species. This observation suggested that a flexible processing scheme will be required if different species are to be recovered using the same process equipment.     

Measurement of power in selectorized strength-training equipment

The author derived the exact analytical expression of the instantaneous joint power in exercises with single-joint, variable-resistance, selectorized strength-training equipment, taking into account all the relevant geometric, kinematic, and dynamic variables of both the movable equipment elements (resistance input lever, cam-pulley system, weight stack) and of the user's exercising limb. A numerical algorithm was also designed to express, in the presence of a cam, the rectilinear kinematic variables of the weight stack as a function of the rotational kinematic variables of the resistance input lever, and vice versa. Given that information, one can measure the value of the instantaneous and mean joint power exclusively by means of a linear encoder placed on the weight stack or, alternatively, only by the use of an angular encoder placed on the rotational axis of the resistance lever. The results highlight that, for knee extension exercises with leg extension equipment, the real values of both instantaneous and mean joint power may differ by more than 50% in comparison with the values obtained by taking into account only the mass and velocity of the weight stack. These differences are notable not only in explosive exercises, but also whenever considerable joint velocities/accelerations occur within the range of motion.     

Aggregation of Escherichia coli B/r A during agar filtration: effect on morphometric measurements.

We have investigated the phenomenon of particle aggregation in a sample of 71,038 Escherichia coli B/r A cells in balanced exponential growth, during preparation for electron microscopy by agar filtration. The bacteria were photographed in a transmission electron microscope and the dimensions and spatial relationships among all the members of each aggregate were recorded using an interactive image processing system. The proportion of aggregated cells, 22%, is much greater than that found by direct count in a light microscope (7%), implying that most aggregation takes place during the preparation stages. The aggregated cells are about 1% narrower than the free cells, because of mutual compression, and 1.5% longer, because of a selection bias in favor of longer cells. From a statistical analysis of the data, we conclude that the clustering of cells into aggregates in the course of sample preparation is the result of random encounters during the settling on the collodion membrane and of the changing surface tension during the drying process. A method is proposed to correct morphometric measurements for the distortion caused by cellular aggregation of this kind.     

Platelet lysis and aggregation in shear fields.

A rotational viscometer was used to study the effects of shear stress on platelets in human platelet-rich plasma (PRP). For 5-min exposure times, shear stresses above 160 dynes/cm2 induced platelet lysis (as determined by release of platelet lactic dehydrogenase). For 30-s exposure times, shear stresses greater than 600 dynes/cm2 were required to induce platelet lysis. The platelet counts of sheared PRP were decreased to as low as one-fifth the original count due largely to shear-induced aggregation. The count is a minimum at intermediate stress levels (200-400 dynes/cm2). Higher stresses induce disaggregation as well as lysis. The diminution in the counts was partially reversed in 2 h incubation after cessation of shearing. Experiments were carried out with three different viscometer configurations so that the shear stress and the solid surface area access could be varied independently. Surface access was not a significant variable in the conditions of the experiments. Thus aggregation and lysis may be induced by stress effects alone as well as by solid surface effects. The results also show that the response of platelets to shear stress is strongly dependent on exposure time. Platelets are much less resistant to shear stress than red cells for relatively long exposure times. However, the converse is true for very short exposure times.     

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.¹ Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.     

Properties and principles of mycelial flow: experiments with a tube rheometer

The flow behavior of a penicillin mash has been investigated with a tube rheometer and compared with rotational viscometer observations. In the low-shear regions plug flow and breakdown of the plug have been studied. For turbulent flow turbulence damping was demonstrated. The Theological development during the fermentation was followed. At low deformation rates the pressure drop increased during the fermentation. In turbulent regions the opposite tendency was observed. The possible underlying flow mechanisms are discussed, and the influence of a number of physical parameters have been investigated.     

A Bio-inspired Collision Avoidance Model Based on Spatial Information Derived from Motion Detectors Leads to Common Routes

Avoiding collisions is one of the most basic needs of any mobile agent, both biological and technical, when searching around or aiming toward a goal. We propose a model of collision avoidance inspired by behavioral experiments on insects and by properties of optic flow on a spherical eye experienced during translation, and test the interaction of this model with goal-driven behavior. Insects, such as flies and bees, actively separate the rotational and translational optic flow components via behavior, i.e. by employing a saccadic strategy of flight and gaze control. Optic flow experienced during translation, i.e. during intersaccadic phases, contains information on the depth-structure of the environment, but this information is entangled with that on self-motion. Here, we propose a simple model to extract the depth structure from translational optic flow by using local properties of a spherical eye. On this basis, a motion direction of the agent is computed that ensures collision avoidance. Flying insects are thought to measure optic flow by correlation-type elementary motion detectors. Their responses depend, in addition to velocity, on the texture and contrast of objects and, thus, do not measure the velocity of objects veridically. Therefore, we initially used geometrically determined optic flow as input to a collision avoidance algorithm to show that depth information inferred from optic flow is sufficient to account for collision avoidance under closed-loop conditions. Then, the collision avoidance algorithm was tested with bio-inspired correlation-type elementary motion detectors in its input. Even then, the algorithm led successfully to collision avoidance and, in addition, replicated the characteristics of collision avoidance behavior of insects. Finally, the collision avoidance algorithm was combined with a goal direction and tested in cluttered environments. The simulated agent then showed goal-directed behavior reminiscent of components of the navigation behavior of insects.     

Ultrasonic monitoring of glycerol settling during transesterification of soybean oil

A low-intensity ultrasonic measurement system was used to monitor the products of transesterification of soybean oil in methanol to FAME (biodiesel). The byproducts of the transesterification reaction are methyl esters, glycerol and other products. During the transesterification reaction, the glycerol, having a higher density than the methyl ester, settles at the bottom of the reaction vessel. The aim of this study was to measure the glycerol deposition rate during transesterification and to assess the reaction rate and end time. Soybean oil was converted into biodiesel at four temperature levels. The amount of catalyst (KOH) used in the transesterification reactions was determined by titration. The ultrasonic waveforms captured during the reaction were recorded and analyzed automatically. The ultrasonic system monitored the effects of reaction temperatures on the glycerol settling rate and the reaction end times. The ultrasonic measurement of glycerol settling would be a useful non-destructive method for evaluating the effects of parameters such as catalyst amount, mixing time and temperature on transesterification reactions.     

Distribution of living polycystine radiolarians in the Gulf of Mexico and Caribbean Sea,and comparison with the sedimentary record

Plankton tows and bottom samples from the Gulf of Mexico and Caribbean Sea were examined to study the distribution, ecology, and preservation of modern radiolarians. Abundances of radiolarians from this region, an area of low primary productivity, are low. Diversities are variable in the surface waters; diversity indices decrease with increasing water depth, indicating that fewer niches are occupied by radiolarians in deep water. Living radiolarians are confined to specific water masses, some species ranging between two masses, and can be used as indicators of these water masses in ecologic or paleo-oceanographic studies.The record of radiolarian tests present in the sediment is dissimilar to the record of living radiolarians in the water column, but is similar to the record of empty tests falling through the water column. This indicates that a considerable length of time is involved in the settling of radiolarian tests. It also confirms the validity of ecologic interpretations based on a study of sediments only.