Aggregation in dilute solutions of high molar mass poly(ethylene) oxide and its effect on polymer turbulent drag reduction

Shetty, Abhishek; Solomon, Michael J.

doi:10.1016/j.polymer.2008.10.026

Cited by 59 publications

(32 citation statements)

References 66 publications

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“…(12) A compact goniometer fitted with a multi-tau digital correlator (ALV-GmbH, Langen, Germany) and 488 nm argon-ion laser (Innova 70C, Coherent, Santa Clara, CA) were used for scattering measurements as we have previously. (17) No significant differences between strains was noted (data not shown).…”

Section: Methodsmentioning

confidence: 84%

Complement C5a Generation by Staphylococcal Biofilms

Satorius¹,

Szafranski²,

Pyne³

et al. 2013

Shock

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Biofilms production is a central feature of nosocomial infection of catheters and other medical devices used in resuscitation and critical care. However, the very effective biofilm forming pathogen Staphylococcus epidermidis often produces a modest host inflammatory response and few of the signs and symptoms associated with more virulent pathogens. To examine the impact of bacterial biofilm formation on provocation of an innate immune response, we studied the elaboration of the major complement anaphylatoxin C5a by human serum upon contact with S. epidermidis biofilms. Wildtype S. epidermidis and mutants of sarA (a regulatory protein that promotes synthesis of the biofilm-forming polysaccharide intercellular adhesin, PIA) and icaB (responsible for post-export processing of PIA) were studied. C5a release, as a function of exposed biofilm surface area, was on the order of 1 fmol cm−2 sec−1 and was dependent on the presence of PIA. Experimental results were used to inform a physiologically-based pharmacokinetic model of C5a release by an infected central venous catheter, one of S. epidermidis' primary means of causing human disease. These simulations revealed that the magnitude of C5a release on a superior vena cava catheter completely covered with S. epidermidis would be lower than necessary to alert circulating leukocytes. Combined, the experimental and computational results are highly consistent with clinical observations in which the clinical signs of central line associated bloodstream infection are often muted in association with this important pathogen.

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Section: Methodsmentioning

confidence: 84%

Complement C5a Generation by Staphylococcal Biofilms

Satorius¹,

Szafranski²,

Pyne³

et al. 2013

Shock

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“…In the present case, the shear rate generated by the turbulent flow would appear to be unable to induce stretching of the individual polymer chains. A previous light scattering study of PEO polymers in aqueous solutions has found that the polymers form clusters (or aggregates) with sizes much larger than the individual polymers [41]. Therefore, a possible scenario is that these clusters are sufficiently large and floppy that they are being stretched by the flow, rather than the individual polymers.…”

Section: Discussionmentioning

confidence: 98%

Enhanced and reduced heat transport in turbulent thermal convection with polymer additives

Wei

Xia

2012

Phys. Rev. E

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We present an experimental study of turbulent Rayleigh-Bénard convection with polymer additives made in two convection cells, one with a smooth top and bottom plates and the other with a rough top and bottom plates. For the cell with smooth plates, a reduction of the measured Nusselt number (Nu) was observed. Furthermore, the amount of Nu reduction increases with increasing polymer concentration (c), reaching ~12% for c = 120 ppm and an apparent leveling off thereafter. For the cell with rough plates, however, an enhancement (~4%) of Nu was observed when the polymer concentration is greater than 120 ppm. This increase in Nu is corroborated by an increased large-scale circulation (LSC) velocity in the same cell when polymers are added. In contrast, the LSC velocity in the smooth cell is found to be essentially the same with and without polymers. It is further found that in the smooth cell the rms values of the global Nu, σ(Nu), and that of the local temperature, σ(T), both exhibit similar dependence on c as Nu itself. In contrast, σ(Nu) and σ(T) in the rough cell are found to be essentially independent of c.

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“…49,50 Using the Stokes–Einstein relation ( D = k B T /6 πη R h , where k B is Boltzmann’s constant, T is temperature, and η is the viscosity), the probability distribution of effective hydrodynamic radii of the scattering specimen is then obtained. 51 Here, the refractive index and viscosity are that of water at the temperature of the measurement. The output of the measurement is the distribution function of the hydrodynamic radius of the specimen.…”

Section: Methodsmentioning

confidence: 99%

Effects of Temperature on the Morphological, Polymeric, and Mechanical Properties ofStaphylococcus epidermidisBacterial Biofilms

et al. 2015

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Changes in temperature were found to affect the morphology, cell viability, and mechanical properties of Staphylococcus epidermidis bacterial biofilms. S. epidermidis biofilms are commonly associated with hospital-acquired medical device infections. We observed the effect of heat treatment on three physical properties of the biofilms: the bacterial cell morphology and viability, the polymeric properties of the extracellular polymeric substance (EPS), and the rheological properties of the bulk biofilm. After application of a 1 h heat treatment at 45 °C, cell reproduction had ceased, and at 60 °C, cell viability was significantly reduced. Size exclusion chromatography was used to fractionate the extracellular polymeric substance (EPS) based on size. Chemical analysis of each fraction showed that the relative concentrations of the polysaccharide, protein, and DNA components of the EPS were unchanged by the heat treatment at 45 and 60 °C. The results suggest that the EPS molecular constituents are not significantly degraded by the temperature treatment. However, some aggregation on the scale of 100 nm was found by dynamic light scattering at 60 °C. Finally, relative to control biofilms maintained at 37 °C, we observed an order of magnitude reduction in the biofilm yield stress after 60 °C temperature treatment. No such difference was found for treatment at 45 °C. From these results, we conclude that the yield stress of bacterial biofilms is temperature-sensitive and that this sensitivity is correlated with cell viability. The observed significant decrease in yield stress with temperature suggests a means to weaken the mechanical integrity of S. epidermidis biofilms with applications in areas such as the treatment of biofilm-infected medical devices.

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Aggregation in dilute solutions of high molar mass poly(ethylene) oxide and its effect on polymer turbulent drag reduction

Cited by 59 publications

References 66 publications

Complement C5a Generation by Staphylococcal Biofilms

Complement C5a Generation by Staphylococcal Biofilms

Enhanced and reduced heat transport in turbulent thermal convection with polymer additives

Effects of Temperature on the Morphological, Polymeric, and Mechanical Properties ofStaphylococcus epidermidisBacterial Biofilms

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