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Shear Device (shear + device)
Selected AbstractsMicrobial strengthening of loose sandLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2010B.L. Banagan Abstract Aims:, To test whether the addition of Flavobacterium johnsoniae could increase the strength of saturated Ottawa 30 sand. Methods and Results:, A box model was built that simulates groundwater-like flow through a main sand compartment. Strength tests were performed at seven locations and at two depths, 10·8 and 20·3 cm below the top of the tank, using a vane shear device before and after the addition of bacteria. After the addition of Fl. johnsoniae, sand samples were obtained from multiple sampling ports on the vertical sides of the box model. The presence of a bacterial biofilm was confirmed by staining these sand samples with SYTO-9 and Alexa Fluor 633 and viewing with a confocal microscope. The average shear strength increases after the addition of Fl. johnsoniae were 15·2,87·5%, depending on the experimental conditions. Conclusions:,Flavobacterium johnsoniae caused a statistically significant increase in the strength of saturated Ottawa 30 sand. Significance and Impact of the Study:, Biofilm-forming bacteria can increase the shear strength of saturated sand. The addition of biofilm-forming bacteria to a building site may be an alternate method to mitigate the effects of liquefaction. [source] Detachment of sprayed colloidal copper oxychloride,metalaxyl fungicides by a shallow water flowPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6 2009Eva Pose-Juan Abstract BACKGROUND: Flow shear stress induced by rainfall promotes the loss of the pesticides sprayed on crops. Some of the factors influencing the losses of colloidal-size particulate fungicides are quantified by using a rotating shear system model. With this device it was possible to analyse the flow shear influencing washoff of a commercial fungicide formulation based on a copper oxychloride,metalaxyl mixture that was sprayed on a polypropylene surface. A factor plan with four variables, i.e. water speed and volume (both variables determining flow boundary stress in the shear device), formulation dosage and drying temperature, was set up to monitor colloid detachment. RESULTS: This experimental design, together with sorption experiments of metalaxyl on copper oxychloride, and the study of the dynamics of metalaxyl and copper oxychloride washoff, made it possible to prove that metalaxyl washoff from a polypropylene surface is controlled by transport in solution, whereas that of copper oxychloride occurs by particle detachment and transport of particles. Average losses for metalaxyl and copper oxychloride were, respectively, 29 and 50% of the quantity applied at the usual recommended dosage for crops. CONCLUSION: The key factors affecting losses were flow shear and the applied dosage. Empirical models using these factors provided good estimates of the percentage of fungicide loss. From the factor analysis, the main mechanism for metalaxyl loss induced by a shallow water flow is solubilisation, whereas copper loss is controlled by erosion of copper oxychloride particles. Copyright © 2009 Society of Chemical Industry [source] Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under ShearingTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Yves Deyrail Abstract Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene-methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break-up times of PC fibers were taken into account. Shear rate and quenching-time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching. La solidification sous cisaillement du polycarbonate (PC) dispersé dans une matrice copolymère éthylène-acétate de vinyle (EMA) a été suivie à l'aide d'un microscope et d'une platine de cisaillement chauffante. Dans un premier temps la déformation isotherme de billes de PC pour différentes températures a été étudiée, ainsi que sa modélisation. Une bonne corrélation avec les modèles issus de la littérature a été obtenue. L'importance du rapport des viscosités a été ainsi soulignée. Dans un second temps le contrôle de la morphologie par le procédé de « refroidissement dynamique » a été expérimenté. Celui-ci consiste à solidifier le PC sous cisaillement pendant le refroidissement. Les temps de rupture des fibres de PC ont été considérés et l'importance du couple gradient de cisaillement-temps de refroidissement sur le contrôle de la morphologie a été mis en évidence. Pendant la solidification, un refroidissement rapide permet d'obtenir une morphologie fibrillaire. [source] Design Optimization of Blood Shearing Instrument by Computational Fluid DynamicsARTIFICIAL ORGANS, Issue 6 2005Jingchun Wu Abstract:, Rational design of blood-wetted devices requires a careful consideration of shear-induced trauma and activation of blood elements. Critical levels of shear exposure may be established in vitro through the use of devices specifically designed to prescribe both the magnitude and duration of shear exposure. However, it is exceptionally difficult to create a homogeneous shear-exposure history by conventional means. This study was undertaken to develop a Blood Shearing Instrument (BSI) with an optimized flow path which localized shear exposure within a rotating outer ring and a stationary conical spindle. By adjustment of the rotational speed and the gap dimension, the BSI is designed to generate shear stress magnitudes up to 1500 Pa for exposure time between 0.0015 and 0.20 s with a pressure drop of 100 mm Hg. Computational fluid dynamics (CFD) revealed that a flow path designed by first-order analysis and intuition exhibited unfavorable pressure gradient, vortices, and undesirable regions of reverse flow. An optimized design was evolved utilizing a parameterized geometric model and automatic mesh generation to eliminate vortices and reversal flow and to avoid unfavorable pressure gradients. Analysis of the flow and shear fields for the extreme limits of the shear gap demonstrated an improvement in homogeneity due to shape optimization and the limitations of an annular shear device for achieving completely uniform shear exposure. [source] Ultra scale-down studies of the effect of shear on cell quality; Processing of a human cell line for cancer vaccine therapyBIOTECHNOLOGY PROGRESS, Issue 5 2009Ryan McCoy Abstract Whole cell therapy is showing potential in the clinic for the treatment of many chronic diseases. The translation of laboratory-scale methods for cell harvesting and formulation to commercial-scale manufacturing offers major bioprocessing challenges. This is especially the case when the cell properties determine the final product effectiveness. This study is focused on developing an ultra scale-down method for assessing the impact of the hydrodynamic environment on human cells that constitute the therapeutic product. Small volumes of a prostate cancer cell line, currently being developed in late phase II clinical trials as an allogeneic whole cell vaccine therapy for prostate cancer, were exposed to hydrodynamic shear rates similar to those present in downstream process, formulation and vial filling operations. A small scale rotating disc shear device (20 mL) was used over a range of disc speeds to expose cells to maximum shear rates ranging from 90 × 103 to 175 × 103 s -1 (equivalent maximum power dissipation rates of 14 × 103 to 52 × 103 W kg -1). These cells were subsequently analyzed for critical cell quality attributes such as the retention of membrane integrity and cell surface marker profile and density. Three cell surface markers (CD9, CD147, and HLAA-C) were studied. The cell markers exhibited different levels of susceptibility to hydrodynamic shear but in all cases this was less than or equal to the loss of membrane integrity. It is evident that the marker, or combination or markers, which might provide the required immunogenic response, will be affected by hydrodynamic shear environment during bioprocessing, if the engineering environment is not controlled to within the limits tolerated by the cell components. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Factors influencing antibody stability at solid,liquid interfaces in a high shear environmentBIOTECHNOLOGY PROGRESS, Issue 5 2009James G. Biddlecombe Abstract A rotating disk shear device was used to study the effect of interfacial shear on the structural integrity of human monoclonal antibodies of IgG4 isotype. Factors associated with the solution conditions (pH, ionic strength, surfactant concentration, temperature) and the interface (surface roughness) were studied for their effect on the rate of IgG4 monomer loss under high shear conditions. The structural integrity of the IgG4 was probed after exposure to interfacial shear effects by SDS-PAGE, IEF, dynamic light scattering, and peptide mapping by LC-MS. This analysis revealed that the main denaturation pathway of IgG4 exposed to these effects was the formation of large insoluble aggregates. Soluble aggregation, breakdown in primary structure, and chemical modifications were not detected. The dominant factors found to affect the rate of IgG4 monomer loss under interfacial shear conditions were found to be pH and the nanometer-scale surface roughness associated with the solid-liquid interface. Interestingly, temperature was not found to be a significant factor in the range tested (15,45°C). The addition of surfactant was found to have a significant stabilizing effect at concentrations up to 0.02% (w/v). Implications of these findings for the bioprocessing of this class of therapeutic protein are briefly discussed. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Prediction of Shear Damage of Plasmid DNA in Pump and Centrifuge Operations Using an Ultra Scale-Down DeviceBIOTECHNOLOGY PROGRESS, Issue 4 2007Hu Zhang Supercoiled circular (SC) plasmid DNA is often subjected to fluid stress in large-scale manufacturing processes. It is thus important to characterize the engineering environment within a particular unit operation as well as within the associated ancillary equipment during process design for plasmid DNA manufacture so as to avoid shear-induced degradation of the SC isoform, which would compromise product efficacy in therapeutic applications. In the past few years, ultra scale-down (USD) tools were developed within our laboratory to mimic the engineering environments experienced by biomolecules within a range of manufacturing-scale ancillary, primary recovery, and purification operations, using milliliter quantities of material. Through the use of a USD shear device, the effect of elongational strain rate on SC plasmid DNA degradation was studied in this paper, and from that, the impact of a centrifugal pump, a Mono pump, and a disk-stack centrifuge feed zone on SC plasmid DNA degradation was predicted and experimentally verified at scale. Model predictions, over the range of conditions studied, were in good agreement with experimental values, demonstrating the potential of the USD approach as a decisional tool during bioprocess design. [source] | |||||||||||||