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Centrifugal Force (centrifugal + force)
Selected AbstractsEFFECT OF CENTRIFUGAL FORCE ON THE AQUEOUS EXTRACTION OF SOLUTE FROM SUGAR BEET TISSUE PRETREATED BY A PULSED ELECTRIC FIELDJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2005KAMAL EL-BELGHITI ABSTRACT In this article, the centrifugal aqueous extraction of solute from sugar beet tissue is investigated at ambient temperature after a pulsed electric field (PEF) treatment. Two kinds of samples of fresh sugar beet were used: a sample with a determined discoid shape and gratings. Both samples were pretreated by a PEF with 250 rectangular pulses of 100 µS each. The PEF intensity was fixed at 940 V/cm for the disk samples and 670 V/cm for gratings. The pretreated samples were placed in distilled water at ambient temperature with a water-to-solid ratio equal to 3 and subjected to different centrifugal accelerations. The centrifugal field significantly enhanced the kinetics of extraction from the electrically pretreated tissues of sugar beet. However, the increase of centrifugal acceleration was only effective up to a certain value (5430 × g for disk samples and 600 × g for gratings). The centrifugal extraction can be assumed to proceed in two stages: a first rapid washing followed by a slow diffusion stage. A two-exponential kinetics model taking into account these two stages was applied and correctly described the centrifugal extraction from beet samples (disks and gratings). [source] Does limb angular motion raise limb arterial pressure?ACTA PHYSIOLOGICA, Issue 3 2009D. D. Sheriff Abstract Aim:, Mechanical factors such as the muscle pump have been proposed to augment flow by several mechanisms. The potential for limb angular motion to augment local perfusion pressure (pressure = ½,r2,2, where , is the fluid density, r the radius and , the angular velocity) has been overlooked. We sought to test the hypothesis that limb angular motion augments limb arterial pressure. Methods:, Nine human subjects performed horizontal shoulder flexion (,±90° at 0.75 Hz for 30 s). We measured finger arterial pressure (photoplethysmography) in the moving (Trial 1) and non-moving arm (Trial 2) in separate trials along with the pressure (strain gauge) generated at the fingers within a length of water-filled tubing mounted on the moving arm in both trials. Results:, Arm swinging raised (P < 0.05) the mean pressure measured in the tubing by 11 ± 2 and 14 ± 2 mmHg (Trials 1 and 2 respectively). In response to exercise, the rise in mean finger arterial pressure in the swinging limb (18 ± 3 mmHg, Trial 1) exceeded (P < 0.05) the rise in the resting limb (8 ± 2 mmHg, Trial 2) by an amount similar to the 11 mmHg rise in pressure generated in the tubing in Trial 1. Conclusions:, We conclude that the swinging of a limb creates centrifugal force (a biomechanical centrifuge) which imparts additional pressure to the arteries, but not the veins owing to the venous valves, which further widens the arterial,venous pressure difference. [source] Expression of Osterix in mechanical stress-induced osteogenic differentiation of periodontal ligament cells in vitroEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2008Yanhong Zhao Osterix (Osx) is an osteoblast-specific transcription factor required for the differentiation of pre-osteoblasts into functional osteoblasts. This study sought to examine the changes of Osx expression in periodontal ligament cells (PDLC) subjected to mechanical force, and to investigate whether Osx is involved in the mechanical stress-induced differentiation of PDLC. Human PDLC were exposed to centrifugal force for 1,12 h. Real-time polymerase chain reaction (PCR), western blot, and immunofluorescence assays were used to examine the mRNA and protein expression of Osx and its subcellular localization. Furthermore, PDLC were transfected with the expression vector pcDNA3.1 flag-Osx and subjected to mechanical force for 6 h. The changes in alkaline phosphatase (ALP) activity and in the expression of core-binding factor alpha1 (Cbfa1), ALP, osteopontin, bone sialoprotein, osteocalcin, and collagen I were measured. After the application of mechanical force, Osx was upregulated in a time-dependent manner at both mRNA and protein levels, and Osx protein was translocated from the cytosol into the cell nuclei. Overexpression of Osx did not affect the expression of Cbfa1, but it significantly enhanced the ALP activity and the mRNA expression of all the aforementioned osteogenic marker genes, all of which increased further under mechanical stress. These results suggest that Osx might play an important role in the mechanical stress-induced osteogenic differentiation of PDLC and therefore be involved in alveolar bone remodeling during orthodontic therapy. [source] Coordination between electoral arenas in multilevel countriesEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 2 2009IGNACIO LAGO This article shows the existence of a coordination dilemma in multilevel countries that hold elections for different parliaments, at different territorial levels and with different electoral rules. With evidence from Spain, the analysis identifies interaction or contamination effects between national and subnational electoral arenas that generate, just as in most mixed-member electoral systems, a centrifugal force that increases the number of electoral parties in national elections. The incentives that solve this coordination dilemma faced by small regional or local parties are theoretically discussed and empirically tested. [source] An unsteady flow structure on a heated rotating disk under mixed convectionHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2005Noriyuki Furuichi Abstract A flow field under mixed convection on a heated rotating disk has been measured using an ultrasonic velocity profiler (UVP). The measured velocity field is a spatio-temporal one as a function of radial coordinates and time. The objective of this paper is to clarify the vortex structure caused by the instability between buoyancy and centrifugal force. The vortex appears under typical conditions of Reynolds numbers and Grashof numbers and it moves toward the outside of the disk. This behavior can be classified into two patterns. The size of the vortex structure decreases with an increasing Reynolds number and increases with the Grashof number. The traveling velocity of the vortex increases with the Grashof number. Moreover, it decreases with an increasing Reynolds number in spite of increasing centrifugal force. According to these results, the region dominated by natural, forced, and mixed convection is classified in the relationship between Reynolds and Grashof numbers. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(6): 407,418, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20074 [source] Effects of operating conditions on infiltration of molten aluminum and heat transfer in a centrifugal force fieldHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2003Qinwei Tian Abstract This paper presents the results of an analysis aimed at determining the influence of changing operating conditions in the centrifugal infiltration casting. It considers the effect of centrifugal force on infiltration and heat transfer. The molten aluminum flow with heat transfer though SiC porous media in a centrifugal force field is described using a mathematical and physical model by employing the local thermal nonequilibrium between the solid and fluid phases. The calculation results show that the temperature difference between molten aluminum and SiC porous media in the infiltrated region decreases with the contact time. There are two distinctly noticeable stages of infiltration velocity: the onset stage of infiltration, which drops down sharply, and the following stage of smooth velocity. The operating conditions have important effects on the infiltration velocity and temperature patterns of fluid and solid. A suitable rotational speed and SiC volume fraction should be chosen to ensure the flow of molten metal in the porous preform and diminish the temperature difference between fluid and solid. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(6): 501,510, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10114 [source] On computation of response of a rotor in deformed configuration using three-dimensional finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 3 2003A. Nandi Abstract The governing differential equations for a rotor are derived in a rotating reference, which rotates about the centre-line of the bearings with a speed equal to the shaft spin speed. The same equations of motion are once solved in the original configuration and once in the deformed configuration. It is observed that, though the analysis is based on small displacement elasticity, the difference in the above solutions is not negligible. It is shown that this can be attributed to the moment resultant caused by the centrifugal force in the deformed configuration. Copyright © 2003 John Wiley & Sons, Ltd. [source] Numerical analysis of turbulent flow separation in a rectangular duct with a sharp 180-degree turn by algebraic Reynolds stress modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2008Hitoshi Sugiyama Abstract Turbulent flow in a rectangular duct with a sharp 180-degree turn is difficult to predict numerically because the flow behavior is influenced by several types of forces, including centrifugal force, pressure-driven force, and shear stress generated by anisotropic turbulence. In particular, this type of flow is characterized by a large-scale separated flow, and it is difficult to predict the reattachment point of a separated flow. Numerical analysis has been performed for a turbulent flow in a rectangular duct with a sharp 180-degree turn using the algebraic Reynolds stress model. A boundary-fitted coordinate system is introduced as a method for coordinate transformation to set the boundary conditions next to complicated shapes. The calculated results are compared with the experimental data, as measured by a laser-Doppler anemometer, in order to examine the validity of the proposed numerical method and turbulent model. In addition, the possibility of improving the wall function method in the separated flow region is examined by replacing the log-law velocity profile for a smooth wall with that for a rough wall. The analysis results indicated that the proposed algebraic Reynolds stress model can be used to reasonably predict the turbulent flow in a rectangular duct with a sharp 180-degree turn. In particular, the calculated reattachment point of a separated flow, which is difficult to predict in a turbulent flow, agrees well with the experimental results. In addition, the calculation results suggest that the wall function method using the log-law velocity profile for a rough wall over a separated flow region has some potential for improving the prediction accuracy. Copyright © 2007 John Wiley & Sons, Ltd. [source] Numerical simulation of turbulent impinging jet on a rotating diskINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2007A. Abdel-Fattah, Article first published online: 25 OCT 200 Abstract The calculations of quasi-three-dimensional momentum equations were carried out to study the influence of wall rotation on the characteristics of an impinging jet. The pressure coefficient, the mean velocity distributions and the components of Reynolds stress are calculated. The flow is assumed to be steady, incompressible and turbulent. The finite volume scheme is used to solve the continuity equation, momentum equations and k,, model equations. The flow characteristics were studied by varying rotation speed , for 0,,,167.6 rad/s, the distance from nozzle to disk (H/d) was (3, 5, 8 and 10) and the Reynolds number Re base on VJ and d was 1.45 × 104. The results showed that, the radial velocity and turbulence intensity increase by increasing the rotation speed and decrease in the impingement zone as nozzle to disk spacing increases. When the centrifugal force increases, the radial normal stresses and shear stresses increase. The location of maximum radial velocity decreases as the local velocity ratio (,) increases. The pressure coefficient depends on the centrifugal force and it decreases as the distance from nozzle to plate increases. In impingement zone and radial wall jet, the spread of flow increases as the angular velocity decreases The numerical results give good agreement with the experiment data of Minagawa and Obi (Int. J. of Heat and Fluid Flow 2004; 25:759,766). Copyright © 2006 John Wiley & Sons, Ltd. [source] Heat transfer reduction at the separation point on a spinning sphere in mixed convectionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2002egül Öztürk Abstract The unsteady laminar thermal boundary-layer flow over an impulsively started translating and spinning isothermal body of revolution in the case of mixed convection is investigated. Velocity components and temperature are obtained as series of functions in powers of time. The general results are applied to a spinning sphere and the development of the surface heat flux evaluated at the separation point as it advances upstream is determined. The surface heat flux evaluated at the separation point as it moves forward decreases due to the increasing magnitude and influence of the centrifugal force and it is augmented by the opposing flow and reduced by the aiding flow. Reduction of the surface heat flux at the separation point is as low as 50 per cent as compared to the heat flux at the front stagnation point. Copyright © 2002 John Wiley & Sons, Ltd. [source] Computational investigation of the mechanisms of particle separation and "fish-hook" phenomenon in hydrocyclonesAICHE JOURNAL, Issue 7 2010B. Wang Abstract The motion of solid particles and the "fish-hook" phenomenon in an industrial classifying hydrocyclone of body diameter 355 mm is studied by a computational fluid dynamics model. In the model, the turbulent flow of gas and liquid is modeled using the Reynolds Stress Model, and the interface between the liquid and air core is modeled using the volume of fluid multiphase model. The outcomes are then applied in the simulation of particle flow described by the stochastic Lagrangian model. The results are analyzed in terms of velocity and force field in the cyclone. It is shown that the pressure gradient force plays an important role in particle separation, and it balances the centrifugal force on particles in the radial direction in hydrocyclones. As particle size decreases, the effect of drag force whose direction varies increases sharply. As a result, particles have an apparent fluctuating velocity. Some particles pass the locus of zero vertical velocity (LZVV) and join the upward flow and have a certain moving orbit. The moving orbit of particles in the upward flow becomes wider as their size decreases. When the size is below a critical value, the moving orbit is even beyond the LZVV. Some fine particles would recircuit between the downward and upward flows, resulting in a relatively high separation efficiency and the "fish-hook" effect. Numerical experiments were also extended to study the effects of cyclone size and liquid viscosity. The results suggest that the mechanisms identified are valid, although they are quantitatively different. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] 3-D simulation and visualization of laminar flow in a microchannel with hair-pin curvesAICHE JOURNAL, Issue 7 2004Y. Yamaguchi Abstract The purpose of the present study was to investigate fluidic behavior in a microchannel with hair-pin curves, using a three-dimensional (3-D) computational fluid dynamics simulation, and to observe the 3-D flow pattern, to validate the simulation. The microchannel used was fabricated on a PMMA plate using a flat-end mill. The channel width and depth were 210 and 205 ,m, respectively, and the radius of each hair-pin curve was 500 ,m. Two liquids; purified water and an aqueous solution of 50 ,mol/L fluorescein, were introduced into the microchannel through different inlets and were merged, forming a side-by-side parallel flow in the straight channel. When the average velocity was 25 mm/s, the liquid was thrust outward by centrifugal force and, as a result, the vertical line that crossed the central axis was distorted after passing the first hair-pin curve. At the second hair-pin curve, the centrifugal force was exerted in the opposite direction, and the distorted line returned nearly to an initial vertical line. When the average velocity was 125 mm/s, however, the vertical line, which was distorted at the first hair-pin curve, did not recover to the initial vertical line after the second curve. The interface between the two liquids was permanently waved. The simulation was in good agreement with the experimental data. The results suggest that the diffusion rate through the interface of two liquids in microchannels with hair-pin curves can increase, compared to that in straight microchannels. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1530,1535, 2004 [source] Centrifugal Gel Casting: A Combined Process for the Consolidation of Homogenous and Reliable CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Saeed Maleksaeedi In this work, a combined process, called centrifugal gel casting (CGC), was proposed for the fabrication of homogenous and reliable monolithic and composite ceramics starting from submicrometer-sized powders. This method exploits the advantages of both conventional gel casting (GC) and centrifugal slip casting (CSC), while overcoming the limitations associated with the two methods. Via this process, a relatively low centrifugal force is applied to form a highly concentrated slurry in the mold cavity, which is then followed by in situ polymerization of slurry during gelation. In this work, concentrated alumina slurries with different solid contents from 45 to 65 vol% were consolidated by the three forming methods mentioned above. Various properties of green and fired products were measured and compared. Shorter processing time, lower centrifugal force, higher green strength, and minimal segregation are observed to be the characteristics of CGC in comparison with CSC. In situ elimination of bubbles with no need for degassing and the ability to remove heterogeneities, on top of high reliability and the potential to process higher viscosity slurries, are the main advantages of this method over the conventional GC. [source] Mechanical flower thinning improves the fruit quality of applesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2010Alexey A Solomakhin Abstract BACKGROUND: Apple ,Golden Delicious Reinders' and ,Gala Mondial' trees were mechanically blossom-thinned with 30,77 × g (300,480 rpm rotation) and 5 or 7.5 km h,1 vehicle speed to improve fruit quality, minimise leaf damage, reduce hand and chemical thinning and to prevent or overcome alternate bearing; adjacent untreated or manually thinned apple trees served as controls. RESULTS: Mechanical thinning (43 × g, 360 rpm, 5,7.5 km h,1) had a positive effect on fruit size (15% larger), firmness (8.4 in Gala vs. 7.6 kg cm,2 in the unthinned control), sweetness (124 vs. 117 g kg,1 sugar in the control), contained the largest malic acid content (4 g kg,1 vs. 3.4 g kg,1 in the control) and 17% more anthocyanin (normalised anthocyanin index = 0.8 in Gala vs. 0.7 in the control); fruit of Golden and Gala showed additionally advanced starch breakdown and ripened earlier. CONCLUSIONS: Since increases in rotor speed, viz. centrifugal force, versus increases in the vehicle speed resulted in opposing effects, an integrated coefficient of thinning (ICT) was devised with optimum values of 10,40 (at 43 × g, 5,7.5 km h,1), where an ICT > 50 led to tree damage and ICT < 8 led to sub-optimum thinning efficacy. Copyright © 2010 Society of Chemical Industry [source] Thermal effects of circumplanetary disc formation around proto-gas giant planetsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009M. N. Machida ABSTRACT The formation of a circumplanetary disc and accretion of angular momentum on to a protoplanetary system are investigated using three-dimensional hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disc is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disc, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disc. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's gas envelope extends farther, and a slightly thick disc appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disc. The disc forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the Solar system, the proto-Jupiter and Saturn have compact discs in the region of r < 21rJup(r < 0.028 rH,Jup) and r < 66rSat(r < 0.061rH,Sat), respectively, where rJup(rH,Jup) and rSat(rH,Sat) are the Jovian and Saturnian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these discs corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact discs around proto-gas giant planets. [source] Development and high stress abrasive wear behavior of milled carbon fiber-reinforced epoxy gradient compositesPOLYMER COMPOSITES, Issue 7 2008Navin Chand Milled carbon fiber-reinforced polysulfide-modified epoxy gradient composites have been developed. Density and hardness increases with the increase of carbon fiber content in the direction of centrifugal force, which shows the formation of gradient structure in the composite. High stress abrasive wear test was conducted on the gradient composites by using a Suga Abrasion Wear Tester. Abrasive wear rate reduced on increase of milled carbon fiber content from 0.15 to 1.66 vol%. Reduction in abrasive wear rate in milled carbon fiber-reinforced epoxy gradient composites has been attributed to the increase of hardness, presence of random milled fibers, and debris of composite materials, which gave resistance and reduced wear rate. There is a small decrease in specific wear rate on adding 0.15 vol% milled carbon fibers. Further decrease of specific wear rate is observed on adding 0.45 vol% milled carbon fibers. After 3 N load, there is a decrease in specific wear rate behavior on adding 0.45 vol% carbon fibers, which further decreases on adding 0.60 vol% of carbon fibers. There is a remarkable decrease in specific wear rate up to 5 N load for 1.66 vol% milled carbon fiber-reinforced composite. Reduction in specific wear rate on adding milled carbon fibers is based on the formation of debris, which remained intact in their respective positions due to the interfacial adhesion between milled carbon fibers and epoxy resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Modélisation de l'efficacité de filtration d'un échangeur cycloneTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2003Richard Caetano Abstract This work is a modelling of the Aireco® filtration system. This heat exchanger, with particle catching capabilities, is made of a cyclonic body which contains refrigerated coils. The water vapour contained in the gas to be treated condensed on the coils surface. Our modelling considers two main capture surfaces: the entry zone in which particles are collected by inertial impaction and the cyclonic body in which particles diffused by centrifugal force is the main phenomena. We found that these considerations explain our experimental results with an accuracy more than 90%, when the Aireco® is on a normal point of working. Ce travail consiste à modéliser l'efficacité de filtration du système d'épuration Aireco®. Cet échangeur épurateur se compose d'un corps cyclonique et de nappes de serpentins réfrigérés provoquant la condensation de la vapeur d'eau contenue dans le gaz pollué traité. Dans ce modèle nous modélisons l'échangeur en considérant les zones de piégeage prépondérantes que sont l'entrée et le corps cyclonique. Notre modèle prend en compte les effets d'impaction inertielle en entrée et la centrifugation dans le corps du système. Cette démarche théorique corrobore à plus de 95 % les valeurs obtenues expérimentalement lorsque l'Aireco® fonctionne dans ses conditions nominales. [source] Research and Development, Regional Spillovers and the Location of Economic ActivitiesTHE MANCHESTER SCHOOL, Issue 4 2004Alberto Franco Pozzolo I present an endogenous growth model that studies the effects of local inter-industry and intra-industry knowledge spillovers in R&D on the allocation of economic activities between two regions. The equilibrium is the result of a tension between a centripetal force, the cost of transporting goods from one region to the other, and a centrifugal force, the cost increase associated with life in a more crowded area. The presence of local knowledge spillovers, which determines the concentration of the R&D activities within one region, also introduces a further centripetal force that makes a symmetric allocation of the economic activities impossible. The concentration of R&D fosters the equilibrium rate of growth of the economy with respect to the case of no-integration, by increasing the positive effect of local knowledge spillovers. Contrary to the findings of the majority of models in the new economic geography literature, within this framework a reduction in transport costs may be associated with a more even geographical distribution of economic activities. [source] Unsteady exact solutions of the flow equations for three-dimensional spherical atmospheresTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008A. Staniforth Abstract Time-dependent, closed-form solutions of the 3D Euler equations describing motion relative to a uniformly rotating coordinate frame are derived. The spherical geopotential approximation is applied but not the shallow-atmosphere and hydrostatic approximations. The solutions correspond to cyclostrophically and hydrostatically balanced vortices that are steady in inertial space and whose symmetry axes do not coincide with the rotation axis of the coordinate frame. The inertial-frame flow velocities are readily transformed to a precisely spherical rotating coordinate system in which the 3D Euler equations contain centrifugal as well as Coriolis terms. In this form the solutions may be used to test numerical models formulated in spherical coordinates under the spherical geopotential approximation, so long as the centrifugal terms are explicitly included as forcing terms. The development is repeated for the hydrostatic and non-hydrostatic primitive equations (with the shallow-atmosphere approximation) and for the shallow-water equations. In the latter case, the required explicit centrifugal force may be provided by a zonally symmetric addition to the free surface height, with an identically equal orographic elevation to ensure conservation of mass. The solutions are then identical to the unsteady shallow-water solutions of Läuter et al. that inspired this study. ©Crown Copyright 2008. Reproduced with the permission of the Controller of HMSO and the Queen's Printer for Scotland. Published by John Wiley & Sons, Ltd. [source] Centrifugal seeding of mammalian cells in nonwoven fibrous matricesBIOTECHNOLOGY PROGRESS, Issue 1 2010Robin Ng Abstract Three-dimensional (3D) cell cultures have many advantages over two-dimensional cultures. However, seeding cells in 3D scaffolds such as nonwoven fibrous polyethylene terephthalate (PET) matrices has been a challenge task in tissue engineering and cell culture bioprocessing. In this study, a centrifugal seeding method was investigated to improve the cell seeding efficiency in PET matrices with two different porosities (93% and 88%). Both the centrifugal force and centrifugation time were found to affect the seeding efficiency. With an appropriate centrifugation speed, a high 80,90% cell seeding efficiency was achieved and the time to reach this high seeding efficiency was less than 5 min. The seeding efficiency was similar for matrices with different porosities, although the optimal seeding time was significantly shorter for the low-porosity scaffold. Post seeding cell viability was demonstrated by culturing colon cancer cells seeded in PET matrices for over 5 days. The centrifugal seeding method developed in this work can be used to efficiently and uniformly seed small fibrous scaffolds for applications in 3D cell-based assays for high-throughput screening. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Classification of Suspensions by Means of Rotating Filter Discs and Autodynamic High-Frequency BackwashingCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2010L. Steinke Abstract A new method for the classification of suspensions by means of rotating filter discs is presented. The classification without a filter cake buildup by means of a single shaft disc filter is possible using the high-frequency autodynamic backwashing method. High-frequency autodynamic backwashing results from an overpressure fluctuation between the filtrate and concentrate sides, resulting in different flow directions of the filtrate volume flow. The main parameters are the centrifugal force acting on the fluid inside the discs in combination with the fact that the discs are slightly inclined. It is demonstrated that the separation of coarse particles is entirely possible. [source] Kinematic and dynamic analysis of open-loop mechanical systems using non-linear recursive formulationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2006Yunn-Lin Hwang Abstract In this paper, a non-linear recursive formulation is developed for kinematic and dynamic analysis of open-loop mechanical systems. The non-linear equations of motion are developed for deformable links that undergo large translational and rotational displacements. These equations are formulated in terms of a set of time invariant scalars and matrices that depend on the spatial co-ordinates as well as the assumed displacement field, and these time invariant quantities represent the dynamic coupling between the rigid-body modes and elastic deformations. A new recursive formulation is presented for solving equations of motion for open-loop chains consisting of interconnected rigid and deformable open-loop mechanical systems. This formulation is expressed by the recursive relationships and the generalized non-linear equations for deformable mechanical systems to obtain a large system of loosely coupled equations of motion. The main processor program consists of three main modules: constraint module, mass module and force module. The constraint module is used to numerically evaluate the relationship between the absolute and joint accelerations. The mass module is used to numerically evaluate the system mass matrix as well as the non-linear Coriolis and centrifugal forces associated with the absolute, joint and elastic co-ordinates. Simultaneously, the force module is used to numerically evaluate the generalized external and elastic forces associated with the absolute, joint and elastic co-ordinates. Computational efficiency is achieved by taking advantage of the structure of the resulting system of loosely coupled equations. The solution techniques used in this investigation yield a much smaller operations count and can more efficiently implement in any computer. The algorithms and solutions presented in this paper are illustrated by using an industrial robotic manipulator system. The numerical results using this formulation are also presented and discussed in this paper. Copyright © 2006 John Wiley & Sons, Ltd. [source] The Discursive Malleability of an IdentityJOURNAL OF LINGUISTIC ANTHROPOLOGY, Issue 1 2006Chaise LaDousa This article employs a dialogic approach, in the parlance of Bakhtin, to explore the ways in which a school smedium,its primary language of instruction, has become a major category of identity in North India. Many people describe themselves and others by invoking attendance at either a Hindi- or English-medium school. The first task of this article is to account for what Bakhtin callscentripetal forcesthat enable people at different positions in terms of class or school experience to use a common duality of Hindiversus English-medium and its attendant social resonances. The second task is to account for the abilities of a teacher to question the inevitability of the medium divide and to radically reframe what is important about schooling. Her abilities derive, in part, from her experiences with schools, attesting to Bakhtin s insight that centripetal forces in language are never total, and that centrifugal forces arise from complex engagements with institutions. [source] Sedimentation behaviour and turbidity of carrot juices in relation to the characteristics of their cloud particlesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2003Martin Reiter Abstract The cloud stability of carrot juices was investigated using physical methods. In contrast to cloudy juices from fruits or other vegetables described so far, complete clarification of juice samples could not be achieved even after ultracentrifugation. Since the density of one particle fraction was almost equal to that of the continuous phase, this fraction was resistant to sedimentation by centrifugal forces up to 60 600 × g in an 8° Brix carrot juice. Cloud stability problems of carrot juices, therefore, are usually associated with bottom sediment formation, but not with visible loss of turbidity. Particle size and density were shown to be decisive for suspension stability, whilst both particle charge and serum viscosity did not show any effect on cloud stability. The reasons for the exceptional stability of the suspended particles are discussed. Based on three particle fractions, a new physical concept could be deduced according to particle size and density explaining the extraordinary suspension stability of carrot juices. Copyright © 2003 Society of Chemical Industry [source] Relationship between Floc Short Range Structure and Sediment Compaction,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2003Mandalena Hermawan Abstract This paper studies the short and long-range structure of silica aggregates using the small angle light scattering technique. Silica particles were made to aggregate by the addition of MgCl2, with and without continuous shear. Two different short-range structures were observed for different aggregation conditions. The small angle light scattering reveals two different floc structures at different length scales, a very compact floc at short length scale and a loose floc at large length scale. The sediments of these flocs were studied by allowing them to settle under gravity and consolidate at different centrifugal forces. The results show that the floc short-range structure is important in governing the compaction behaviour of sediment. [source] | |||||||||||||||||||||||||