A study of the effect of shear rate on the inherent and intrinsic viscosities of polystyrene fractions, in dilute solution was carried out. Inherent viscosities were determined for five fractions (of molecular weights ranging from 2.9 x 10 to 4.8 x 106); in three solvents (Benzene, Toluene and Methyl Ethyl Ketone); at five temperatures (from 15°C to 85°C); and shear rates ranging from 1.0 x 103 to 2.8 x 104 sec.-1. Inherent viscosities thus determined were extrapolated to zero rate of shear and the extrapolated values plotted against concentration to determine intrinsic viscosities at zero rate of shear, [N] D=0 The inherent viscosity decreased with increasing shear rate. The slope of the curve of inherent viscosity vs shear rate was found to increase (ie become more negative) with increasing concentration, temperature and molecular weight and to be less in a poor solvent than in a good solvent. At very high molecular weights the value of inherent viscosity was found to decrease non-linearly with shear rate. The intrinsic viscosity was found to decrease with increasing shear rate. The slope of the [N] vs D curve was found to increase with increasing molecular weight and decreasing temperature; the slopes were smaller the poorer the solvent. For the three lower fractions the intrinsic viscosity was found to decrease with increasing temperature, very slightly in Methyl Ethyl Ketone and appreciably in Benzene and Toluene, the relative being greater at higher molecular weights. With the two highest fractions this trend was reversed. The slope of the [N] D=0 vs T curve becoming less negative (and actually positive for Benzene end Toluene). The [N] vs T curves ( [N] at free fall) for the three lower fractions were parallel to those at zero rate of shears but of lower intrinsic viscosity values. With the two highest fractions, the slope of the [N] vs T curve became less negative but not to as great a degree as was found with [N] D=0 vs curves. Intrinsic viscosities obtained at zero rate of shear were applied to the Flory-Fox theory. Calculated intrinsic viscosities for polystyrene fractions in Benzene and Toluene were found to agree to within+-4% of the experimental results. For Methyl Ethyl Ketone a wide variation in values was obtained. / Thesis / Master of Science (MS)

In this study, Reometer AR2000 is used to investigate the effect of shear rate on viscosity of emulsion. And a model for the effective viscosity of emulsion is established. Moreover, another model for the hydrodynamic lubrication with binary mixtures of non-Newton fluids is developed. The coupled modified Reynolds are solved by combining the advanced multilevel method with the Newton-Raphson method. The effect of shear rate on lubrication characteristics of hydrodynamic lubrication of emulsion is investigated in cold rolling process. Research results show that the viscosity of emulsion is decreased with increasing the shear rate. Hence,the oil film thickness, oil preasure and oil concentration under hydrodynamic lubrication are increased with decreasing the slide-to roll ratio. Emulsion will be Newton fluid under high shear rate. In the cold rolling process, the emulsion shows the high shear rate, and the elastic deformation of roller and strip are considersd. Hence the end point of plastic zone of strip is moved to oulet zone due to the lubricated zone is increased, so that the film thickness is higher than that for rigid body. When roller radius is increased, the effective elastic modulus and the thickness reduction of strip are decreased, then the lubrication characteristics in cold rolling process are influenced by elastic deformation. When the rolling speed is increased , the inlet film thickness is increased, and the roll torque is slightly increased, but the rolling force and peak preasure are almost not influenced.

Few studies have compared cortisol responses to psychological and physical stress tasks with or without social evaluation. Flow-mediated dilation (FMD) with reactive hyperemia is impaired following acute stress though less is known regarding the impact of stress and cortisol on FMD with exercise induced increases in shear stress (EX-FMD). The purpose of this study was 1) to compare cortisol responses between the Trier Social Stress Test (TSST) and 5min cold pressor test with and without social evaluation (CPT, CPT+SE) and 2) to examine the impact of these stressors and cortisol elevation on EX-FMD. 59 healthy male subjects were randomly assigned to one of three conditions: TSST, CPT, or CPT+SE. Brachial artery EX-FMD was assessed before, 15 and 35min post-stress with Echo and Doppler ultrasound. Results are mean ± SD. Baseline parameters did not differ between conditions (p>.05) and stress responses were similar between the three conditions for peak cortisol: TSST 11.34±5.53nmol/L; CPT 10.08±4.48nmol/L; CPT+SE 8.51±3.60nmol/L; condition effect p=.292; cortisol responders only (increase >2nmol/L) TSST 12.48±5.24nmol/L; CPT 12.13±5.31nmol/L; CPT+SE 10.70±2.86nmol/L; condition effect p=.560; peak MAP: 131.99 ±18.56mmHg, condition effect p=.664; peak TPR: 25.84 ± 9.78mmHg/L/min, condition effect p=0.841; peak stress rating out of 10: 5.11 ± 2.12, condition effect p= 0.292; with the exception of HR (TSST: 95.06 ± 15.29bpm; CPT: 79.00 ± 11.85bpm; CPT+SE: 77.98 ± 7.66bpm; condition effect p= 0.003) and pain ratings out of 10 (TSST: 1.21 ± 1.72; CPT: 6.66 ± 1.42; CPT+SE: 6.38 ± 1.73; condition effect p<.001). Shear stress was lower in the 15min post-stress vs. pre stress and 35min post-stress trials (72.34 ± 4.46; 15min post-stress: 70.79 ± 5.39; 35min post-stress: 70.60 ± 6.10; condition effect p= 0.592; trial effect: p= 0.018). EX-FMD increased from pre- stress to 15min post-stress in all conditions (pre-stress 6.22 ± 2.75%; 15min-post stress: 7.91 ± 3.24%; 35min post-stress: 6.60 ± 2.93%; trial effect p<.001). No correlation between change in EX-FMD and change in cortisol was detected (r2= 0.0125; p=.404). In conclusion, the TSST, CPT and CPT+SE elicited similar stress responses and stress transiently enhanced EX-FMD. Cortisol responses did not explain the enhanced EX-FMD post stress. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2012-09-14 15:41:33.325

Chronic Venous Insufficiency (CVI) is a disease of the lower limbs that affects millions of people in the United States. It is categorized by constant venous hypertension, which can lead to swelling of the legs, pain, skin changes and ulcers. One of the widely known symptoms that can lead to CVI is varicose veins. The main source of the problem of CVI is incompetent venous valves. The purpose of venous valves is to direct blood through the veins to the heart and prevent retrograde flow to the lower limbs. CVI can be caused by leg injury, pregnancy, genetics, age, and prolonged standing. Current treatments of the disease include compression stocking therapy, ablation, vein stripping, and valve reconstruction. CVI has become such a problem for patients, especially those with secondary incompetence in the deep veins, because the current treatments are used to alleviate the symptoms of the disease but do not treat the source of the problem. One solution that has great potential is to create an implantable venous valve that could restore function of the venous system. In the past many prosthetic venous valves have been made, but none are clinically used because of problems with biocompatiblility, thrombogenicity caused by high shear rates, and longterm functionality that has been hindered by leaflet stiffening. The purpose of this research was to create a venous valve that could overcome these difficulties. This was done by designing the valve out of carbon-infiltrated carbon nanotubes (CI-CNTs). This material has been proven to be thrombo-resistant, biocompatible due to its non-reactive properties, and durable. The valve was designed to be initially open and to close with physiological pressures. The shear rate caused by implantation of the valve was minimized to reduce the likelihood of thrombus formation. FEA and CFD analysis was performed to verify the valve would function under physiological conditions and that shear rates would be in the normal range. The final design was tailored for implantation in the common femoral vein. It had a diameter of 12.7 mm, length of approximately 40 mm, and thickness of 0.3 mm. With a hydrostatic pressure of 20 mmHg it fully closed with a maximum stress of 117 MPa, which is below the ultimate strength of CI-CNTs. The CFD analysis demonstrated the valve would cause a maximum shear rate of 225.1 s

Phenol formaldehyde (PF) is the oldest known synthetic polymer. This polymer has seen many applications throughout history, including jewelry, electric wire insulation, and resins used to make adhesives. Today, PF resins are still crucial components used in the wood products industry. These PF resins are formulated into adhesives used to make plywood and various other wood composite products. For example, in the United States, 90 % of the homes are still frame homes that use plywood for construction. The PF adhesives used to make these composites are formulated using agricultural waste products like walnut shells and corn-cob residue. These organic waste products act as fillers that reduce the cost, increase the viscosity, and affect the rheology of the fillers. Wheat flour is added as an extender to reduce cost and affect the tack of the adhesive. These organic fillers are lignocellulosic materials that are made of lignin, cellulose, and hemicellulose. Not much is known about the interactions of these organic fillers and the polymer resin. Rheological studies in our lab have shown that not all of the additions to the adhesive formulation are inert components in the adhesive. The steady-state flow curve analysis of PF adhesives revealed that there is a liquid structure change that occurs at high shear rate. This structure change is observed as a viscosity increase that occurs after applying a maximum shear rate of 4000 1/s. A rheological analysis was conducted to determine the source of this change, with individual components added to the resin. The PF base resin (with nothing added) has a Newtonian rheological behavior. When wheat flour is added to the resin, the overall viscosity increases, and shear thinning occurs at highe shear rates. There is no final viscosity change observed on with the addition of wheat flour. Adding corn-cob residue to the resin increased viscosity, led to some shear thinning at higher shear rates, and allowed the viscosity changes observed in the fully formulated adhesives. These experiments showed that the liquid structural changes that occur in the adhesives are attributed to the organic fillers. All organic fillers used in our studies, including corn-cob residue, walnut shell, almond shell, and Alder bark produce different levels of viscosity change in the PF adhesive formulations. These biomass materials have varying amounts of lignocellulosic content, particle size distributions, and particle shape. Among the fillers, corn-cob residue was shown to cause the most viscosity change compared to any of the fillers. Corn-cob residue is unique compared to the others because it has undergone acid digestion to convert its xylans to furfural. During the viscoelastic oscillation studies, the corn-cob residue filled adhesives showed that they developed network structures in response to a high shear rate that were not observed using the other fillers. With the discovery of these network structures, the next goal of this research was to correlate the effects observed on the rheometer to relevant adhesive application technology like high shear spraying. The corn-cob residue adhesive was sprayed at approximately 70,000 1/s compared to the 4000 1/s of rotational shear on the rheometer. The viscoelastic oscillation studies revealed that there was no network structure formation after high-shear spraying. Further, there was no change observed in the flow curve analysis after spraying the adhesive. This study showed that there are limitations when trying to correlate changes that happen in adhesives during spraying, where extensional forces dominate compared to shear forces. In future research, there is the opportunity to explore the effects of extensional deformation that occurs during the atomization of the adhesive, which will be more reflective of the changes that occur during spraying. / Doctor of Philosophy / Phenol-formaldehyde adhesives are crucial products in the home construction industry. These adhesives are used to make plywood that is used to build frame homes, which represent approximately 90 % of the homes in the United States. These phenol-formaldehyde adhesives are made using organic materials repurposed from agricultural waste products like corn cobs, walnut shells, almond shells, and tree bark. These products help to enhance the properties of the adhesive, reduce the cost, and reduce the amount of resin used. The goal of this research is to understand better the interactions between the adhesive and the organic fillers using rheology. Rheology is a field that studies how materials change and flow with applied external forces. This is an important field because it provides information on viscosity and viscoelastic behavior. Our research has shown that in response to high shear rates, the viscosity of these phenol-formaldehyde adhesives increases. Studying these changes can lead to a better understanding of how these materials change during industrial spraying. This understanding could lead to improved building adhesive materials in the home construction industry.

No description available.

Les biofilms bactériens se développent sur toute interface liquide-solide dès que les conditions sont favorables. Ils correspondent à des assemblages de microcolonies qui baignent dans une matrice extracellulaire polymérique. Parmi les facteurs contrôlant le développement des biofilms, l’hydrodynamique est un paramètre clé qui affecte la morphologie et la composition du biofilm. Nous nous intéressons plus particulièrement dans cette thèse à l'influence du gradient de vitesse pariétal sur la formation du biofilm. Pour cela, nous utilisons un réacteur Couette-Poiseuille qui permet de travailler sous écoulement laminaire stable dans différentes conditions d'écoulement. Les biofilms obtenus après circulation d'eaux usées, sont prélevés sur des coupons et visualisés par microscopie confocale à balayage laser. Différents paramètres caractérisant la morphologie du biofilm sont déterminés après reconstruction 3D de leur structure à l'aide du modeleur GOCAD. Nous montrons que le transport convectif constitue une étape essentielle dans la formation initiale du biofilm, et qu'un gradient pariétal nul permet d'inhiber le développement de celui-ci / Bacterial biofilms develop on any solid-liquid interface whenever conditions are appropriate. They correspond to microcolony assemblages embedded in an extracellular matrix. Among the factors controlling biofilm growth, hydrodynamics is a key parameter affecting both biofilm morphology and composition. In this thesis we investigate the influence of hydrodynamics, and more precisely the wall shear rate effect on biofilm development. For this purpose, a Couette-Poiseuille reactor, allowing to work under stable laminar flow with different flow velocities, was used. Biofilms grown from urban wastewater on coupon surfaces were observed with confocal scanning microscopy. A 3D modeling using GOCAD software was established, thus allowing the determination of various biofilms structural characteristics. The results show the essential role of convective mass transport in biofilm formation, actually a zero wall shear rate inhibited bacterial deposition, and hence biofilm growth

Cardiovascular disease, mostly atherosclerosis, is responsible for one third of all deaths globally, rising to more than 50% in the Western World. Risk factors include smoking, diet, and familial history. Doppler ultrasound can provide estimates of blood velocity and wall shear rate. Clinically, maximum velocity is used to categorise patients for surgery, although Doppler velocity measurement is prone to errors and in need of validation. Wall shear stress—which can be derived from wall shear rate—plays a role in disease initiation and progression, although its clinical utility is unclear due to difficulties associated with its measurement. This thesis investigates the use of Doppler ultrasound as a tool to estimate blood velocity and wall shear rate. A simplified method for estimation of wall shear rate in healthy arteries is developed that uses spectral Doppler ultrasound. This method is based upon the theory of oscillatory flow in rigid pipes, requiring two measurements that are readily available with clinical ultrasound machines. This method is compared to a similar method based on colour flow imaging. The spectral Doppler method underestimated the theoretic value of wall shear rate by between 7 and 22%, with results varying between phantoms. Errors for the colour method were on average 35% greater. Test measurements from one healthy volunteer demonstrated that this method can be applied in-vivo. In more advanced stages of disease, peak velocity distal to a stenosis is of clinical interest and the simplified method for wall shear rate estimation is invalid. Steady flow in a series of simplified stenosis geometries was studied using a dual-beam Doppler system to obtain velocity vectors. These measurements were compared with data from an equivalent system that used particle image velocimetry (PIV) and was considered the gold standard. For Reynolds numbers at the stenosis throat of less than 800, flow remained laminar over the region studied, although distal flow separation did occur. For higher throat Reynolds numbers—corresponding to more severe stenoses or increased flow rates—asymmetric recirculation regions developed; the transition to turbulence occurred more proximally, with a corresponding reduction in stenotic jet and recirculation length. Qualitative agreement was observed in the velocity profile shapes measured using ultrasound and PIV at throat Reynolds numbers less than 800. Above this threshold the qualitative agreement between the velocity profiles became poorer as both downstream distance and the degree of stenosis increased. Peak axial velocity distal to the stenosis was underestimated, on average, by 15% in the ultrasound system. Estimation of shear rate remained difficult with both experimental techniques. Under a Newtonian approximation, the normalised wall shear stresses agree qualitatively. Under pulsatile flow conditions using an idealised flow waveform, superior qualitative agreement was observed in the velocity profiles at diastole than at systole. Similar to the steady flow behaviour, this agreement deteriorated with stenosis severity. The current generation of clinical ultrasound machines are capable of estimating the wall shear rate in healthy arteries. In the presence of significant arterial disease, errors in the peak velocity may result in mis-selection of patients for surgery, while estimation of the wall shear stress remains extremely problematic; particularly with identifying the wall location and measuring velocities close to the wall.

Small diameter synthetic vascular grafts have yet to be clinically successful due to luminal narrowing from thrombosis and intimal hyperplasia. Current attempts to address this issue include the development of materials that support endothelialisation and protein modification to the material surfaces that reduce thrombosis. The extracellular matrix protein elastin has been found to be one of the least thrombogenic components of blood vessels, and its purified and recombinant forms have shown reduced thrombogenicity in both in vitro and in vivo models. Biomaterial coatings of elastin-like polypeptides (ELPs) recombinantly produced in the Woodhouse laboratory showed reduced fibrinogen adsorption, platelet adhesion, and platelet activity. However, the reason for their relative non-thrombogenicity is still not fully understood. In this work, the leukocyte response to ELP-coated materials was investigated. In particular, ELP1 and ELP4, which differ in molecular weight and sequence length, were physically adsorbed to a polyethylene terephthalate surface (MylarTM), yielding 0.22 ± 0.13 μg/cm2 and 0.37 ± 0.19 μg/cm2 surface coverage, respectively, as determined by the colorimetric assay, FastinTM Elastin. These surfaces were exposed to flowing citrated whole blood for surface and bulk evaluation of leukocyte activity using scanning electron microscopy and flow cytometry, respectively. Little leukocyte activation was observed on the surface of the controls, low-density polyethylene and uncoated MylarTM. In the bulk, tissue factor (TF) expression (monocytes: ELP1 = 38.6 ± 16.3 %, ELP4 = 33.9 ± 18.1 %) and platelet-leukocyte aggregates determined by CD61 (monocytes: ELP1 = 63.1 ± 17.1 %, ELP4 = 61.8 ± 16.8 %; granulocytes: ELP1 = 62.7 ± 17.0 %, ELP4 = 60.5 ± 20.1 %) were both decreased compared to uncoated MylarTM, while CD11b upregulation (monocytes: ELP1 = 18.7 ± 2.2 %, ELP4 = 19.7 ± 2.7 %; granulocytes: ELP = 21.4 ± 3.7 %, ELP4 = 22.0 ± 3.2 %) was increased. The statistical dependence of TF expression and platelet-monocyte aggregates was tested; however, no correlation was found. Overall, platelet-leukocyte aggregate formation was reduced and there were conflicting results with regards to the reduction of leukocyte activation for the ELP coatings on MylarTM. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-10-10 15:34:51.802

Properly preparing the drilling fluid is an essential part of any successful drilling operation, especially in complex operations like deviated and horizontal drilling. Understanding the flow behavior of the polymers used in the drilling fluids under different conditions takes a key part in this preparation. In this study, shear rheology of some traditionally used water soluble polymers in drilling and completion fluids / namely PAC (polyanionic cellulose) and xanthan gum, were investigated experimentally. Instead of an oilfield standard Fann Model 35 Viscometer, an Ofite Model 900 Viscometer was used because of its capability to measure at ultra-low shear rates. Effects of the concentration of the polymer, time of shear applied, test temperature and effects of aging were examined. Rheological measurements were conducted between the shear rate ranges of 0.01 to 1000s-1 with concentrations changing from 0.25 to 1.5 grams of polymer per 350 milliliters of water (equivalent to 0.25 to 1.5 lb/bbl). Rheograms were constructed to identify the effect the polymers in question have on the flow characteristics of the drilling fluid. An appropriate constitutive model was used to define the flow behavior of the polymer in question mathematically. It was observed from the constructed rheograms that increase in polymer concentration results in consistent increase of apparent viscosity. Amount of time of shear does not affect the selected polymers if they are dynamically aged at least for two hours. Also as expected increasing temperature of the sample lowers the apparent viscosity considerably.