Tesis: "Centrifugation"

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Astorsdotter, Jennifer. "Dewatering Cellulose Nanofibril Suspensions through Centrifugation." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215079.

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Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal. A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements. Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data <3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions. Cellulosa nanofibriller (CNF) är ett förnybart material med unika styrkeegenskaper. En svårighet med produktion av CNF är att CNF suspensioner innehåller stora mängder vatten. Om volymerna av CNF suspensioner kan minskas med avvattning genom centrifugering, då kan transport- och lagerkostnader sänkas. Målet med det här examensarbetet är att undersöka vilken inverkan olika parametrar har på CNF-avvattning genom centrifugering och identifiera optimala förhållanden för maximalt avlägsnande av vatten. En laboratoriestudie utfördes på fyra olika material. De fyra materialen är 2 w% enzymatiskt behandlad CNF (CNF1), 1.9 w% karboxymetylerad CNF (CNF2) och två kommersiella prover (1.9 w% CNFA och 1.8 w% CNFB). Den huvudsakliga metoden var analytisk centrifugering upp till maximalt 2330 g. De testade parametrarna var initial koncentration innan centrifugering, temperatur, NaCl tillsats, pH, och applicerat fast kompressionstryck (g-kraft och ytvikt). Förutom centrifugeringsexperimenten så karaktäriserades the fyra mmaterialen med laser diffraktion, UV-vis absorption, dynamisk ljusspridning och vägningar av torrhalt. Analys av den experimentella data som insamlats visar att en ökad initial koncentration ger en högre slutkoncnentration, men mindre vatten kan bortföras. Temperaturförändringar har ingen effekt på separation av CNF och vatten. Vid ett applicerat fast kompressibelt tryck på 3 kPa och en initial koncentration 1.5 w% kan koncentrationerna 5.5 w%, 1.5 w%, 4.0 w%, och 4.3 w% nås för CNF1, CNF2, CNFA, och CNFB. Efter extrapolering av polynoma funktioner passad till experimentell data förutspås att koncentrationerna 9.1 w%, 1.5 w%, 6.9 w%, och 7.9 w% kan nås för CNF1, CNF2, CNFA, and CNFB vid 22 kPa och en initial koncentration på 1.5 w%. Förtjockningen av CNF suspensioner som kan, eller förutspås kunna nås genom centrifugering i det här examensarbetet innebär att det är möjligt att avlägsna stora mängder vatten, till exempel kan vatteninnehållet i CNF1 minskas från 65.7 liter/kg CNF till 10.0 liter/kg CNF vid 22 kPa fast kompressionstryck. Koncentrationerna vid 22 kPa fast kompressionstryck är extrapolerade från exprimentell data <3 kPa fast kompressionstryck. Den karboy- metylerade CNF2 kan inte avvattnas om den inte späds ut eller om salt eller pH justeras. Detta är direkt kopplat till de elektrostatiska krafterna i suspensionen och Debye längden. Tillsats av salt eller sänkt pH eliminerar också de koncentrationsgradienter som kan förekomma i utspädda centrifugerade CNF2 suspensioner.

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Keles, Serhat. "Fine Coal Dewatering Using Hyperbaric Centrifugation." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/37807.

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The solid-solid separation processes employed by modern coal preparation plants require large amounts of process water that must be removed from the surfaces of particles using mechanical dewatering equipment. Unfortunately, the existing processes that are used to dewater fine particles are inefficient in terms of moisture reduction and/or solids recovery. Many coal preparation plants are forced to discard fine coal particles because of the inability of existing technologies to reduce the moisture content of this product to an acceptable level. In light of this problem, a new ultrafine dewatering process called hyperbaric filter centrifugation (HFC) has been developed. This novel method combines centrifugation and pressure filtration within a single process to substantially reduce moistures over what can be achieved using conventional dewatering systems. In the current study, steady-state and dynamic dewatering models were developed in order to be able to simulate the behavior of the HFC technology. The steady-state model, which was based on grain-size properties, used empirical expressions to predict product moistures. On the other hand, the dynamic model was based on fundamental theories of filtration and centrifugation. Although the dynamic model provided a better understanding of the working principles of the process, the steady-state grain model produced more accurate equilibrium moisture predictions. Therefore, the steady-state model was used to further investigate the effects of several parameters on cake moistures. As such, the steady-state model was useful for scale up and design purposes. The steady-state dewatering model was also used to perform an economical analysis of potential applications of the HFC technology. The model was used to investigate a variety of new circuit designs that have the potential to be commercially applied in the coal industry. The results clearly showed that this new technology would allow coal companies to process difficult-to-dewater ultrafines using the HFC process, while coarser solids would be more appropriately dewatered using conventional technologies such as vacuum filters or screenbowl centrifuges. This â split dewateringâ concept would provide substantially higher profitability due to lower moistures and higher recoveries of ultrafine solids than could be achieved using a single dewatering process. Laboratory- and pilot-scale versions of this technology has been constructed and tested at the facilities of Mining & Minerals Engineering Department of Virginia Tech. Results of this testing program showed that 30-50% lower moisture values than the ones obtained using conventional mechanical dewatering processes could be achieved with the HFC technology. Based on these promising results, a pilot-scale prototype unit, which was tested successfully at several commercial U.S. coal plants, was also constructed by Decanter Machine, Inc. Finally, the process of developing of this novel technology was successfully completed with the sale of the first full-scale commercial unit by Decanter Machine, Inc. to a major U.S. coal producer. Ph. D.

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Chen, Fei Ph D. Massachusetts Institute of Technology. "Magnetically enhanced centrifugation for continuous biopharmaceutical processing." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51565.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009. Includes bibliographical references. Effective separation and purification of biopharmaceutical products from the media in which they are produced continues to be a challenging task. Such processes usually involve multiple steps and the overall product loss can be significant. As an integrative technique, high gradient magnetic separation (HGMS), together with the application of functional magnetic particles, provides many advantages over traditional techniques. However, HGMS has a number of drawbacks; and its application is limited because it is inherently a batch process and it is difficult to recycle the magnetic nanoparticles. This thesis explores the development of a new type of continuous magnetic separation process, called magnetically enhanced centrifugation (MEC), which exploits the interactions of magnetic particles with magnetic field gradients, forced convective flows and large centrifugal forces. Magnetically susceptible wires in a uniform magnetic field facilitate the capture and aggregation of magnetic particles on wires, and a centrifugal force perpendicular to the magnetic force conveys the particle sludge parallel to the wires in a continuous mode. The primary focus of this thesis is multi-scale modeling and simulation to understand the underlying physics of MEC processes. The potential of MEC as an effective unit operation for biopharmaceutical downstream processing has been demonstrated. Unlike traditional batch-mode HGMS, MEC has a great advantage in that it can be operated continuously as magnetic particles captured on wire surface are constantly removed. (cont.) A dimensionless model for simulating the trajectories of magnetic particles in combined magnetic and flow fields has been developed. The model was first applied to single wire configurations and then extended to multi-wire arrays. It was shown that modified rhombic arrays can provide high capture efficiency while maintaining low pressure drop. It is also shown that capture efficiencies based on results for clean, particle-free wires, may be seriously in error because the particle buildup that accumulates on the wire significantly distorts the flow and the magnetic fields and thus influences the particle trajectories. The dynamic buildup growth process was treated as a moving-boundary problem. Simulation results have shown that the capture efficiency decreases dramatically as particle buildup volume increases. In addition, the influence of particle chaining under magnetic dipole-dipole forces on separation efficiency has been investigated. Magnetic particles form chains as soon as they enter a background magnetic field, and are captured in the form of particle chains. The hydrodynamic force on particle chains was calculated using a 3-D CFD simulation. The capture radius calculated with considering the chaining effect is few times as great as the capture radius calculated assuming individual particles. Bench-top MEC experiments have shown that magnetic particle buildup generally comprises two layers with distinct structures: a spiky layer with all chains parallel to the magnetic field, and a densely-packed layer near the wire. (cont.) This unique structure reflects the dominance of magnetic forces near the wire and of magnetic dipole-dipole interactions at locations further from the wire. As more and more particles accumulate on the wire surface, the centrifugal force can overcome the cohesion of the layer or the adhesion of the layer to the wire, leading to movement of the buildup material. The onset of such movement can be achieved either by increasing the centrifugal force or by increasing the buildup height. Energy and force analyses have been carried out to study various scenarios of buildup movement. For monodisperse magnetic particles, four scenarios can be expected: chain-like layer collapsing down (I), rigid body movement (II), buildup breakage (III), and mixed behavior of rigid body movement and buildup breakage (IV). A set of design formulas were derived to predict buildup structure and different scenarios. Useful scenario and operating regime diagrams were obtained. A discrete element modeling (DEM) package was developed to study the dynamics and rheological behavior of highly concentrated magnetic particle systems. For monodisperse magnetic particles, simulation results confirmed the four regions of the scenario diagram as predicted by force arguments. For polydisperse magnetic particles, DEM simulations showed that the buildup exhibits solid-like behavior when centrifugal effects are small, and liquid-like behavior with a continuous velocity profile when centrifugal effects are large. (cont.) DEM simulations were able to predict the three dimensional effects, including the buildup profiles at the wire tip. Taken together, the results of this work provide a general strategy that can be used as a starting point for the design, evaluation, and optimization of magnetically enhanced processes that are suitable for biopharmaceutical downstream processing. by Fei Chen. Ph.D.

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Duda, Kevin R. 1979. "Squat exercise biomechanics during short-radius centrifugation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38525.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Vita. Includes bibliographical references (p. 178-187). Artificial gravity (AG) created by short-radius centrifugation is a promising countermeasure to the physiological de-conditioning that results from long-duration spaceflight. However, as on Earth, gravity alone does not ensure fitness. We will need to supplement passive exposure to AG with physical exercise to achieve a comprehensive countermeasure. Before AG exercise can be deemed safe and effective, we must understand how Coriolis accelerations and a gravity gradient affect our biomechanics and how centrifuge-based exercises differ from Earth-upright ones. Two experiments were designed to investigate the squat biomechanics while upright in the laboratory and while lying supine on a horizontal, clockwise-rotating short-radius centrifuge at speeds up to 30 revolutions per minute. Constant force springs provided additional resistive force up to 25% of body weight. Dependent measure included the three-dimensional position of the left and right knee, left and right foot reaction forces, and muscle activity. We investigated the Coriolis-induced mediolateral knee perturbations and the sensory-motor after-effects from a multiple repetition protocol. The upright and centrifuge biomechanics were compared for similarities and differences between them. In addition, a two-dimensional kinematic model was developed to predict foot reaction forces, Coriolis accelerations, and joint torques. (cont.) Our results show that mediolateral knee travel during the AG squats was 1.0 to 2.0 centimeters greater than Earth-upright squats. Increasing the rotation rate or adding resistive force did not affect the results. The peak foot forces increased with rotation rate, but rarely exceeded 200% body weight. The ratio of left-to-right foot force during centrifugation was non-constant and approximately sinusoidal, suggesting a postural correction for the Coriolis accelerations. There was a qualitative difference in the foot force vs. knee angle profile between upright and centrifuge-supine because of the centripetal acceleration. Muscle activity, however, was qualitatively similar between the conditions. The kinematic model was used to evaluate the exercise safety and extend the results to larger-radius centrifuges. We conclude that centrifugation provides a unique and challenging environment for exercise and that a brief artificial gravity squat can be carried out safely. The results are extended to cycle ergometry, when possible, and recommendations are made for future AG squat protocols. Supported by NASA Grant NNJ04HD64G and the MIT-Italy Program Progetto Roberto Rocca. by Kevin Ronald Duda. Ph.D.

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Stuhtmann, Gesa [Verfasser]. "Density gradient centrifugation of stallion semen / Gesa Stuhtmann." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2011. http://d-nb.info/1019427086/34.

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Pouly, Jeremie M. "A parametric study of vestibular stimulation during centrifugation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35291.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. "February 2006." Includes bibliographical references (p. 155-160). Artificial Gravity (AG) provided by short-radius centrifugation is a promising countermeasure to the health problems associated with long duration human spaceflight. Head-turns performed during centrifugation, however, trigger a disturbing vestibular response that is only qualitatively understood. In order to design an efficient incremental adaptation procedure, the present study investigates the quantitative aspect of the vestibular side effects associated with AG, in particular, the relationship among crosscoupled stimulation, vestibular response, and adaptation. We tested 20 young adults with supine right-quadrant yaw head-turns performed in a dark environment during short-radius centrifugation. We studied the changes in vestibular response and adaptation to head-turns at different levels of cross-coupled stimulation. Nine combinations of head-turn angle (20°, 40° or 80°) with centrifugevelocity (12, 19 or 30 rpm) were tested over two consecutive days. (cont.) There were four key findings: 1. All measures, except the slow-phase velocity (SPV) peak amplitude of the vestibulo-ocular reflex, decrease significantly between the two experimental days, which demonstrates that significant adaptation is achieved. 2. Large head-angles lead to longer vertical vestibulo-ocular reflex time-constants than smaller angles do, but do not lead to greater adaptation. 3. In the nose-up position, the perceived body-tilt is highly correlated with the true tilt of the gravito-inertial force at mid-chest level. 4. The SPV-peak amplitude and all subjective ratings except body-tilt show significant correlation with the intensity of the cross-coupled stimulus (CCS): the larger the CCS, the stronger the vestibular response. by Jeremie M. Pouly. S.M.

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Bagur, Eric. "Les mélanges nutritifs injectables : étude granulométrique par centrifugation." Bordeaux 2, 1995. http://www.theses.fr/1995BOR2P078.

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Garrick-Bethell, Ian 1980. "Cross plane transfer of vestibular adaptation to human centrifugation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17770.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. Includes bibliographical references (p. 101-106). Human short-radius centrifugation (SRC) is being investigated as a volume-efficient means of delivering intermittent doses of "artificial gravity" to counter the deleterious effects of long exposures to weightlessness. Rotation rates on short radius centrifuges are high to provide the needed g-loading, and therefore entail a variety of unusual vestibular stimuli when certain head movements are made. Since these movements can elicit inappropriate nystagmus, illusions of tumbling, and motion sickness, efforts have been made to adapt people to the stimuli. So far these efforts have been successful in showing that people will adapt to at least one plane of head motion, the yaw (transverse) plane, during supine head-on-axis rotation. However, astronauts must be adapted to all planes of head motion if they are to function normally on the centrifuge. If adaptation to yaw head turns transferred to some extent to pitch (sagittal) plane turns, or any other plane of motion, it would greatly simplify and hasten the adaptation process. To investigate if transfer of adaptation across planes is possible, 10 subjects in the Experimental Group performed a sufficient number of yaw plane head turns to demonstrate adaptation. Adaptation was indicated by decreases in metrics of the off-axis vestibuloocular reflex induced by the head turns, and by subjective ratings of illusory motion. A block of pitch movements was performed before and after the yaw movements, and these two pitch blocks were compared to assess how much adaptation to pitch head turns had taken place. The same procedure was followed on a subsequent day. A Control Group of 10 subjects performed only the blocks of pitch turns, and their adaptation was compared to the adaptation to pitch turns measured in the Experimental (cont.) Group. While both Control and Experimental Groups showed statistically significant signs of adaptation to pitch head turns, we failed to find any significant differences between the amounts of adaptation. If true, this result implies that adaptation to SRC may need to be performed one plane of motion at a time. Additionally, it implies that the brain and vestibular system does not build up a generalized model of SRC stimulation, but rather builds adaptation one input at a time. by Ian Garrick-Bethell. S.M.

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Bruni, Sylvain 1981. "Artificial gravity : neurovestibular adaptation to incremental exposure to centrifugation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/26749.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Includes bibliographical references (p. 115-122). (cont.) not build up adaptation, all subjects in the experimental group who completed the protocol showed signs of adaptation to the stimulus. Only one subject did not complete the five sessions, setting the drop-out rate at about 14%. If this conclusion holds true with more subjects, then a better protocol of adaptation has been unveiled. In order to counteract the debilitating effects of the space environment on the human body, short-radius intermittent centrifugation is investigated as a possible means to expose astronauts to artificial gravity. Whereas AG is efficient in providing stimuli for muscles, bones and cardiovascular system, short-radius centrifugation elicits discomfort and illusory sensations of motion if particular head movements are made while spinning. Past research has shown that human beings can adapt to these sensations and undergo various stimuli without the disturbing effects of motion sickness, sensations of tumbling and inappropriate eye movements. However, current protocols for adaptation basically consist in repeated exposure to the discomfort. This solution is not satisfactory because the drop-out rate oscillates between 30 and 50%. Since it is not acceptable to spend days of training on astronauts who, in the end, because of this training, could become unsuitable for flight, it is of primary importance to find a training protocol that achieves adaptation without going through permanent discomfort. Incremental exposure to centrifugation is expected to be a compromised protocol to bring trainees to adaptive level without exposing them to maximum discomfort. Seven subjects were exposed to centrifugation during a five-day protocol, over which the speed of rotation was progressively increased. As in previous protocols of adaptation, subjects performed provocative head movements at all speeds. A control experiment had ten subjects exposed to centrifugation without making head turns, in order to verify to what extent the experimental conditions of measurement impact the subjects' behavior and reactions. While subjects in the control experiment did by Sylvain Bruni. S.M.

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Edmonds, Jessica Leigh. "Exercise protocols during short-radius centrifugation for artificial gravity." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45273.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008. "June 2008." Includes bibliographical references (p. 125-133). Long-duration spaceflight results in severe physiological deconditioning, threatening the success of interplanetary travel. Exercise combined with artificial gravity provided by centrifugation may be the comprehensive countermeasure needed to prevent such deconditioning. The aims of this study were (1) to characterize the physiological responses to longitudinal g-gradient and high g-levels during short-radius centrifugation, and (2) to quantify the fitness benefits of an eight-week exercise program on a short-radius centrifuge. In the first experiment, we utilized a tilting short-radius centrifuge to investigate heart rate, blood pressure, and calf volume responses to high g-level and g-gradient centrifugation with and without light exercise (stepping in place). All measures increased significantly with increasing g-level and increasing g-gradient, but these effects were reduced significantly when the subject stepped in place. In the second experiment, we quantified the effectiveness of an eight-week exercise program using a stair-stepper and resistive arm bands on a horizontally-rotating short radius centrifuge. Healthy, previously sedentary subjects exercised at a constant heart rate three times per week for eight weeks, and underwent measurements to test aerobic capacity and endurance, strength, and body composition at weeks 0, 4, and 8. Eight subjects successfully completed 24 exercise sessions with little or no discomfort. After eight weeks of exercise, we found significant improvements in aerobic capacity (increased work rate for a given heart rate, increased stepping endurance), muscular strength (increased number of push-ups), and body composition (decreased leg fat percentage, increased pelvic bone mineral content). (cont.) Stepping in place significantly reduced the physiological responses to increasing g-level and g-gradient, suggesting that subjects may be able to better tolerate exposure to high-g centrifugation if they exercise. Further, an eight-week exercise program using a stair-stepper on a short-radius centrifuge resulted in improvements to aerobic capacity, strength, and body composition. These two studies demonstrate the feasibility and benefits of exercise in an artificial gravity environment. by Jessica Leigh Edmonds. Ph.D.

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BURLET, REBUFFEL HELENE. "Fatigue thermomecanique : application aux outillages de coulee par centrifugation." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0077.

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Burlet, Hélène. "Fatigue thermomécanique application aux outillages de coulée par centrifugation /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37603522s.

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Touron, Emmanuel. "Étude et modélisation de la destruction d'agrégats de colloïdes par les contraintes de cisaillement crées dans un séparateur centrifuge /." Gif-sur-Yvette : Direction de l'information scientifique et technique, CEA Saclay, 1996. http://catalogue.bnf.fr/ark:/12148/cb35837917z.

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Elias, Paul Z. (Paul Ziad). "Incremental adaptation to yaw head movements during 30 RPM centrifugation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35579.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. Includes bibliographical references (p. 84-89). Artificial Gravity (AG) provided by short-radius centrifugation is a promising countermeasure against the harmful physiological effects of prolonged weightlessness. However, the vestibular stimulus associated with making head movements while rotating presents a challenge. During a head movement, the semicircular canals are excited by a cross-coupled angular acceleration, resulting in tumbling sensations, perceived body tilt, non-compensatory vertical nystagmus, and motion sickness. Past experiments in the Man Vehicle Lab have studied adaptation to yaw head movements while rotating at 23 RPM. To investigate adaptation to head movements at a higher rotation rate, 28 subjects participated in a 3-Day protocol in which centrifuge velocity was incremented from 14 RPM on Day 1, to 23 RPM on Day 2, to 30 RPM on Day 3. Key findings included: 1) 24 subjects completed the protocol with average motion sickness levels remaining below 5 (out of 20). Feasibility of head movements at 30 RPM was demonstrated, suggesting that adaptation to higher rotation rates may be possible. (cont.) 2) A motion sickness model used in conjunction with a quantitative semi-circular canal sensory conflict model and an adaptation parameter was effective in making general predictions of motion sickness and adaptation over the 3 days. 3) Intensity and duration of tumbling sensations adapted significantly over the 3 days. 4) The VOR time constant decreased significantly over the 3 days and appeared to reach a limit of approximately 3.5 seconds, which is near the estimated cupular time constant. by Paul Z. Elias. S.M.

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Fontenot, Robin L. "Tube centrifugation for processing platelet-rich plasma in the horse." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76971.

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Platelet-rich plasma (PRP) is a popular treatment for equine tendon and ligament injuries; however, commercial PRP systems are expensive. Development of a safe, inexpensive alternative would make PRP therapy more widely available to horse owners. The purpose of this study was to evaluate the quality and bacteriologic safety of PRP produced by three simple, inexpensive tube centrifugation methods and compare the results to a commercial system. Citrated blood collected from 26 normal horses was processed by four methods: blood collection tubes centrifuged at 1200 and 2000 x g, a 50ml conical tube, and a commercial system. Platelet and cell counts and mean platelet volume (MPV) in whole blood and PRP were determined using an automated hematology analyzer. Results were analyzed using mixed model ANOVA with post-hoc comparisons (MPV and fold change for RBC, WBC, and platelets) and binary logistic generalized estimating equations with horse as a blocking factor (absolute numbers of WBC, and platelets). Aerobic and anaerobic cultures were performed. Significance was set at p<0.05. Mean platelet concentrations ranged from 1.55 to 2.58 fold. The conical tube method produced the highest number of PRP samples with platelet concentrations of greater than 2.5-fold and within the clinically acceptable range of >250,000 platelets/?l. WBC counts were lowest using the commercial system and unacceptably high using the red top methods. The incidence of bacterial contamination was low (2.1%). Based on these results, the conical tube method may be a suitable alternative to commercial PRP systems in cases with budgetary constraints. Master of Science

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Molin, Elin. "Evaluation of different centrifugation settings using BD Microtainer® tubes." Thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305970.

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In order to keep the turnaround time it is desirable to have few centrifugal programs and be able to centrifuge microtainer tubes together with vacutainer tubes. BD has launched a new type of microtainer tube that got a lower g-force than the older one on the same centrifugation program. The aims was to compare this program and three other, more powerful, programs and compare the impact on some common analytes and serum indices, especially on hemolysis. Three test parts was performed using venous samples taken from healthy individuals, 1) transfer of whole blood from serum tube to microtainer tubes, a clinical chemistry analysis; 2) whole blood from plasma tube to microtainer tubes, a clinical chemistry analysis and 3) whole blood from plasma tube to microtainer tubes for platelet count analysis. All tubes were examined for gel formation. The result showed a significant variance between some settings for some analytes but foremost at 899g and at 2000g, both in 10 min. The platelet count was below the threshold limit at 2000g. No tube had insufficient formation of the gel. The setting of 2000g was found suitable for microtainer tubes. These results correspond with the recommended settings from BD. Further studies are needed with more analytes and test subjects and a simulated transport time for plasma, because of the increased risk for hemolysis, to confirm if the same setting can be used for microtainer tubes (899g) as for the older microtainer tube and vacutainer tube (1300g).

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Akin, Faith W., Owen D. Murnane, Amber Pearson, Stephanie Byrd, and J. Kip Kelly. "Normative Data for the Subjective Visual Vertical Test during Centrifugation." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/1784.

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Background: The otoliths act as gravito-inertial force sensors and contribute to the perception of spatial orientation. The perception of gravitational vertical can be assessed by asking a subject to adjust a light bar to the vertical. Prior to clinical use of the SVV (subjective visual vertical) test, normative data and test-retest reliability must be established. Purpose: To obtain normative data and d etermine the test-retest reliability for the SVV test performed in static and dynamic test conditions. Research Design: A descriptive design was used to obtain normative data. Study Sample: Twenty-four young adults with no history of neurological disease, middle-ear pathology, open or closed head injury, cervical injury, or audiovestibular disorder participated in the study. Data Collection and Analysis: The SVV angle was measured in the static position and in three dynamic conditions: (1) on-axis clockwise (CW) rotation, (2) off-axis CW rotation of right ear, and (3) off-axis CW rotation of left ear. Results: In young healthy individuals, the SVV was Conclusions: The normative data obtained in this study may be useful in identifying patients with chronic utricular dysfunction. We recommend the use of difference angles (on-axis SVV ‐ off-axis SVV) to remove baseline bias and decrease the variability of the SVV angles for the off-axis conditions.

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18

Akin, Faith W., Owen D. Murnane, A. Pearson, Stephanie M. Byrd, and J. K. Kelly. "Normative Data for the Subjective Visual Vertical Test during Centrifugation." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etsu-works/1936.

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19

Zhang, Jianfeng. "Sensibilité et stabilité dans l'estimation des perméabilités relatives et de la pression capillaire à partir de mesures de laboratoire." Paris 9, 1994. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1994PA090011.

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Nous étudions le problème d'identification des perméabilités relatives et de la pression capillaire associé aux équations aux dérivées partielles gouvernant des déplacements diphasiques en milieu poreux dans des expériences de centrifugation. Pour déterminer la qualité des résultats d'identification, nous effectuons une analyse de sensibilité pour le problème d'identification linéarisé. Enfin nous appliquons numériquement la théorie de la quasi-convexité pour réaliser une étude de stabilité non-linéaire

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20

HUMPICH, ISABELLE. "Utilisation de l'elutriation dans la purification des cellules sanguines : application aux monocytes." Strasbourg 1, 1989. http://www.theses.fr/1989STR15022.

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21

Waite, Jessica Arlene. "Cushioned centrifugation of stallion semen: factors impacting equine sperm recovery rate and quality." Thesis, Texas A&M University, 2007. http://hdl.handle.net/1969.1/85886.

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Centrifugation of stallion semen is an integral part of the cryopreservation procedure, primarily allowing for the concentration of sperm and removal of seminal plasma. In addition, centrifugation is required for maximizing spermatozoal quality in semen from some stallions subjected to cooled transport, because of the detrimental effects of long-term exposure to high levels of seminal plasma. The centrifugation process, however, has potential deleterious effects, including reduction in sperm quality as well as loss of sperm numbers. Since centrifugation plays such a crucial role in semen processing, two experiments were designed to evaluate more efficient centrifugation methods to meet the demands of the equine industry. In Experiment 1, semen was centrifuged in two different tube types (nipple- or conical-bottom), using a cushioned technique (Eqcellsire® Component B) with two different extenders (opaque-INRA96 or clear-HGLL). For Experiment 2, nipple-tube centrifugation was conducted at two different g forces (400 or 600) for 20 min, using three different iodixanol cushion media, Eqcellsire® Component B, OptiPrep[TM], or Cushion Fluid[TM]. Regardless of tube or extender types, centrifugation of semen resulted in sperm recovery rates ≥90%; however, centrifugation in INRA 96 extender yielded higher sperm motility values than did centrifugation in HGLL extender (P < 0.05). Cushion type or g force did not impact post-centrifugation semen quality, based on the laboratory values measured (P > 0.05). These results indicate that cushioned centrifugation of stallion semen in either conical-bottom or nipple-bottom tubes can yield a high sperm harvest, while maintaining sperm function. An optically opaque extender, as is typically used in the equine breeding industry, can be used to achieve this goal. The fertility rate (94%; 131/140) following cushioned semen centrifugation in a commercial program this past year indicates that these laboratory results are transferable to the clinical setting.

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22

FIKRI, MOHAMMED AMINE. "Simulation numerique 3d, en collocation chebyshev, de phenomenes thermoconectifs en centrifugation." Paris 11, 1993. http://www.theses.fr/1993PA112166.

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Dans cette these est faite une analyse numerique des effets de la force de coriolis sur un ecroulement de thermoconvection dans une experience de croissance cristalline sous centrifugation en centrifugation bridgman stabilisante. Pour cela nous avons mis au point un code de calcul resolvant les equations de navier-stokes tridimensionnelles pour des fluides incompressibles par une methode spectrale de collocation chebyshev. Ce code a ete valide sur le probleme classique de la cavite carree et cubique differentiellement chauffees. Cette etude a montre que la centrifugation n'a qu'un role de deflection sur l'ecoulement thermoconvectif pris comme reference et qu'il faut tenir compte d'autres ingredients dynamiques pour pouvoir comprendre les resultats experimentaux. Ceci pourra etre fait, par exemple, en couplant les equations de navier-stokes avec une equation traduisant les effets des poussees thermosolutales. Le code que nous avons developpe est prevu pour cela

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23

Lajoye, Luc. "Mise en forme par centrifugation de matériaux composites à matrice métallique." Grenoble INPG, 1988. http://www.theses.fr/1988INPG0044.

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24

Lajoye, Luc. "Mise en forme par centrifugation de matériaux composites à matrice métallique." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376148869.

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25

Mexson, Joanne. "Selective isolation and taxonomic analysis of the genus Micromonospora." Thesis, University of Kent, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342134.

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26

Borel, Philippe. "Etude expérimentale et modélisation de la filtration centrifuge : application au dimensionnement des essoreuses." Toulouse, INPT, 1986. http://www.theses.fr/1986INPT006G.

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On peut definir une methodologie de dimensionnement des essoreuses centrifuges a cycles. Proposition d'un modele mathematique fonde essentiellement sur l'equation de filtration adaptee aux filtres centrifuges. Pour caracteriser le milieu poreux on utilise une cellule de compression permeabilite (c. C. P. ) et une essoreuse de taille reduite. Cette c. C. P. Permet de donner une approche theorique de la filtration centrifuge, et peut etre un outil pour le dimensionnement des essoreuses. Il y a une bonne concordance entre le modele mathematique et les resultats experimentaux. Ce meme modele, ainsi que le programme de calcul correspondant, permettent d'optimiser un cycle d'essorage centrifuge

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27

Basim, Gul Bahar Jr. "Fine Coal Dewatering." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35680.

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Fine coal constitutes a relatively small portion of a product stream in a coal cleaning plant. However, its processing cost is approximately three times higher than the cost of processing coarse coal. Therefore, many coal companies chose to discard the fines to refuse ponds, causing a loss of profit and creating environmental concerns. This problem can be solved by developing more efficient fine coal dewatering processes, since bulk of the cost associated with processing fine coal is due to dewatering. For this reason, Virginia Tech has developed new chemicals that can increase the efficiency of mechanically dewatering coal fines. To determine the performance of the novel reagents on fine coal dewatering, laboratory vacuum filtration and centrifugation tests were conducted. The utilization of the novel dewatering aids in the dewatering systems decreased the final moisture contents of the filter cakes to sufficiently low values. There was approximately 50% reduction in the cake moisture of many coal samples with the usage of the novel dewatering aids. The tests were performed on various coal samples from different coal preparation plants. This gave the advantage of testing the novel dewatering aids at many different conditions since each sample had its own characteristics. The vacuum filtration tests were extensively used to compare the efficiency of each novel reagent in dewatering. The best performing dewatering aids were determined and they were further utilized to analyze the effects of operational variables, such as; drying cycle time, cake thickness, vacuum pressure level and slurry temperature on dewatering. A statistical analysis was also performed to observe the effect of each factor quantitatively. The analyses were very useful in terms of determining the synergistic effects of these factors in dewatering of fine coal. The centrifuge tests were conducted to examine the efficiency of the novel reagents in a different dewatering application. The experimental results showed a significant improvement in centrifuge dewatering with the usage of proper coal sample. The moisture contents of fairly thick cakes decreased down to 5-10%. This outcome was very satisfactory since most of the dewatering aids commonly used in the coal industry were observed to increase the final cake moisture in centrifuge dewatering instead of decreasing it. Finally, surface chemistry analyses were performed on the coal samples and slurries to analyze the changes in the chemistry of the dewatering system in the presence of the novel dewatering aids. It was observed that there was a favorable improvement in the system chemistry, which was helpful in terms of decreasing the cake moisture content. These observations were also consistent with the results of the dewatering tests. The combined effect of the novel additives in decreasing the surface tension of the slurry and increasing the contact angle of the coal surface at the same time was concluded to be the reason for their significant performance as dewatering aids. Master of Science

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28

Lopez, Daniel. "Comportements collectifs de bactéries en géométrie contrôlée et sous l'effet de la centrifugation." Paris 6, 2013. http://www.theses.fr/2013PA066614.

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Escherichia coli est une bactérie dotée de flagelles lui permettant de se mouvoir dans un liquide. Les trajectoires de ce mouvement sont analogues à celles d'une marche aléatoire à 3 dimensions. Capable de puiser l'énergie de son environnement pour maintenir son mouvement, elle est un paradigme active autopropulsée. Les systèmes de particules actives autopropulsées ont déjà fait l'objet de nombreuses études mais le comportement de ces systèmes soumis à un champ de force homogène est encore mal compris. Ce travail a premièrement consisté à développer un dispositif exprimental afin de pouvoir visualiser l'influence de la centrifugation sur une population de bactéries. Les résultats reproductibles obtenus sur les profils d'équilibre de sédimentation nous ont permis de proposer un modèle de sphère solide afin de décrire le comportement de ce système. Par ailleurs, dans des géométries confinées, les bactéries E. Coli sont capables grâce à leur chimioactisme de se déplacer collectivement. Elles peuvent alors former des ondes de concentration. Ce travail a permis de déterminer comment de telles ondes de concentration réagissaient à des perturbations provoquées par des variations géométriques de l'environnement. L'ensemble des résultats expérimentaux obtenus peuvent être interprétés avec des arguments qualitatifs simples. Finalement nous confrontons ces résultats expérimentaux à ceux obtenus par des simulations issues de modèles cinétiques Escherichia coli is a flagellated bacterium. It swims in liquids following trajectories that are all well described by a 3D random walk. E. Coli uptakes energy from its environment in order to maintain its movement, therefore it's an example of self-propelled particle (SPP). Many systems of SPP have been studied but it's still not clear how these systems react under a homogeneous force field. In this work we have designed an exprimental setup to study the effect of centrifugation on a bacteria population. We have obtained reproducible results of sedimentation profiles at equilibrium. These results are well described in a hard sphere model framework. In confined geometries, E. Coli bacteria are able to move collectively using their chemotaxis. It can lead to the formation of concentration waves. In the second part of this work, we have determined how these bacterial waves react to perturbations induced by geometrical changes of their environment. All experimental results can be interpreted with simple qualitative arguments. Finally we compare these with those obtained by experimental simulation results from kinetic models

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29

Martinez, Georges. "Phénomènes de transfert lors de la solidification dans le procédé de coulée centrifuge horizontale." Grenoble INPG, 1987. http://www.theses.fr/1987INPG0070.

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Etude des effets convectifs lors de la solidification des tubes en acier dans une coquille centrifuge d'axe horizontal. Caracterisation des differents ecoulements. Modelisation de la solidification (semi-analytique, en differences finies)

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30

Wong, Heng Ho. "Modelling studies of the interaction between homogenisation, centrifugation and inclusion body dissolution /." Title page, contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phw8718.pdf.

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31

Sheehan, Scott E. (Scott Eugene). "The effect of head turn velocity on Cross-coupled Stimulation during centrifugation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38652.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. "February 2007." Includes bibliographical references (p. 88-93). Artificial Gravity (AG) has been suggested as a potential countermeasure to the deleterious physiologic effects of long-duration space flight. Short-radius centrifugation (SRC) provides a practical means of producing AG, though perceptual side-effects may potentially limit its operational feasibility. Head-turns in the rotating environment of SRC produce Cross-coupled Stimulation (CCS), which the subject perceives as a tumbling sensation. Acutely, the CCS tumbling sensation is nauseagenic, though adaptation has been shown to diminish this detriment over time. The force environment of CCS suggests that the head-turn velocity plays a role in determining the stimulus magnitude, though the degree to which has not been characterized. In order for SRC to be an operationally viable alternative for AG, it must be shown that the motion sickness symptoms can be controlled without sacrificing adaptation. Modulation of head turn velocity has been suggested as a means to that end. A total of 23 subjects were subjected to right quadrant head-turns of 8 different velocities while spinning at 19 and 23 RPMs in the rotating environment of SRC. (cont.) The perceptual effects were characterized with subjective and objective metrics, investigating the acute differences between velocities as well as the chronic effects on adaptation. The following key results were obtained: 1. A threshold of HT Velocity exists above which an asymptotic perceptual response is observed, and below which the resulting perceptual response diminishes at a logarithmically increasing rate. 2. The effects of HT Velocity are independent of HT direction, with differing head-turn directions produce contextually specific stimuli. 3. HT velocity modulation could provide a practical means of incremental adaptation. by Scott E. Sheehan. S.M.

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32

Khavari, Faraz. "Towards monodisperse Silicon Nanocrystals: density gradient centrifugation applied on commercial gold nanoparticles." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-186172.

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The application of silicon nanocrystals as non-toxic bio-labels and downconverters requires their uniform size distribution in order to minimize the inhomogeneous broadening of the photoluminescence peak. In this thesis, we set the basis for their size-separation via the density-gradient centrifugation method. To be more precise, we successfully apply this technique to separate 5 and 10 nm gold nanoparticles from an ensemble by using an engineered medium layer stack. In addition, we explain how atomic force microscopy is used to measure the size of the nanoparticles, with a particular attentionon the removal of unwanted solvent-related effects. As a future plan, we will implement the technique for the size-separation of silicon nanocrystals.

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33

Brown, Erika Lynn 1978. "Artificial gravity : the role of visual inputs in adaptation to short-radius centrifugation." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82245.

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34

De, Cuypere Peter. "Vers une conduite intégrée des procédés industriels : application à un système de centrifugation." Nancy 1, 2000. http://www.theses.fr/2000NAN10020.

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La complexité des procédés industriels rend parfois l'application de lois de commande conventionnelles inadaptées. En effet, dans certaines situations, le système de commande doit présenter un degré d'autonomie de manière à assurer une continuité dans la tâche pour laquelle il a été conçu. Dans ce mémoire, une nouvelle approche de l'architecture fonctionnelle d'un système de supervision est proposée. Cette architecture a pour but d'accroître l'autonomie des procédés industriels en intégrant au système de supervision les quatre fonctions que sont : les fonctions de commande-conduite, la base de connaissances, le mécanisme d'inférence et l'interface homme-machine. Le chapitre 2 est consacré à l'étude du processus de centrifugation. Le fonctionnement global du système est représenté sous forme d'un graphe signé prenant en compte l'influence des différents phénomènes intervenant dans le processus. Le chapitre 3 traite du problème de l'apprentissage à partir de données. Différentes approches telles que la classification, la reconnaissance de formes, la régression, sont présentées et appliquées au système. La dernière partie de ce chapitre est consacrée aux modèles flous de type Tagaki-Sugeno. Le chapitre 4 est dédié à l'étude des fonctions de surveillance, diagnostic et accommodation aux défauts. La dualité entre l'approche espace de parité et l'analyse en composantes principales (ACP) pour la détection et l'isolation des défauts est mise en évidence. Dans la suite du chapitre, le concept de l'accommodation de la commande aux défauts est exposé et une approche particulière consistant à déterminer des paramètres de commande pour le système défectueux est détaillée. Finalement, la dernière partie du mémoire met en évidence les mécanismes permettant d'intégrer les différentes fonctions au procédé de supervision In the design of control systems for complex industrial processes there are needs that cannot be successfully addressed by the existing conventional control laws. In certain situations, the control system must exhibit a degree of autonomy in order to ensure continuity in the task for which it has been designed. In this work, a new approach for the functional architecture of a control system is proposed. The goal of this architecture is to increase the industrial processes autonomy by integrating in the control system the four following functional modules : control functions, knowledge base, inference mechanisms and man-machine interface and communications. Chapter 2 is dedicates to the study of the centrifugation process. The global behaviour is described by an oriented-signed graph taking into account the influence of the different phenomena. Chapter 3 deals with the problem of data-based learning systems. Different learning approaches, such as classification, pattern recognition and regression are presented and applied to the system. The last part of the chapter is devoted to the Takagi-Sugeno type fuzzy models. In chapter 4, the problems of monitoring, fault diagnosis and accomodation are treated. The dualty between parity space approach and principal component analysis (PCA) for fault detection and isolation is shown. In the last part of the chapter, the principles of fault accomodation are exposed and a specific method based on the computation of the faulty system parameters is applied. Finally, the procedure which leads to the integration of the functions to the control system is presented

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35

Wearne, Susan. "Spatial orientation of the human linear and angular vestibulo-ocular reflexes during centrifugation." Thesis, The University of Sydney, 1993. https://hdl.handle.net/2123/26488.

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Six independent co-ordinates comprising three rotational and three translational degrees of freedom are required to specify the orientation and motion of a body in inertial space without ambiguity. The vestibular sensors of the inner ear are designed to provide the organism with precisely this information: three approximately orthogonal semicircular canals and two otoliths (utricle and saccule) on either side of the head transduce the three angular and three linear degrees of freedom, respectively. Activation of either angular or linear vestibular sensors results in compensatory reflexes including an angular VOR (AVOR), various linear VOR's (LVOR's) and the vestibulo-spinal reflexes which mediate static and dynamic postural control. The combined input from the vestibular labyrinth thus serves to orient the body and stabilise the eyes during head movement in any spatial plane. The vestibular sensors are not tied to any particular muscle group; they drive a number of motor systems with disparate physical requirements and functions. How this brainstem system accurately and reflexively partials out the relevant information in the source signal to drive a particular compensatory reflex is the subject of several different sensory-motor modelling approaches. Recent evidence suggests that, analogous to a modern inertial guidance system, the vestibular system uses frequency-selective filtering, realised in the physical properties of the endorgan, and the hair cell receptors, to effect the appropriate channelling. Considerable interspecies variation in the frequency response of the VCR reflects the range of natural movements of different animals. Analogously, variation in the working ranges of different body movements within a species should be reflected in differential frequency-tuning of the various vestibule-ocular and vestibule-spinal reflexes. Evidence for frequency-selective filtering of all vestibulo-ocular reflexes is presented in the following chapters, and a case developed for a peripheral filtering system which generates appropriate canal-ocular and otolith-ocular reflexes during combined, often ambiguous linear and angular acceleration stimulation.

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36

Mesguich, Frederic. "Stratégie innovante pour la mise en forme de nanostructures TiO2/Au à propriétés synergétiques pour le photovoltaïque." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00978847.

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Actuellement, le secteur des nanotechnologies est en développement intense. Les nanoparticules de dioxyde de titane et d¿or occupent une part importante de ce secteur, avec des applications utilisant principalement leurs propriétés optiques et catalytiques. Les synergies pouvant exister entre les nanoparticules d¿or et leur support, en particulier via l¿effet plasmon, permettent de modifier la réponse optique de dispositifs catalytiques ou photovoltaïques. Une nouvelle technique polyvalente de mise en forme de film mésoporeux à base de nanoparticules de dioxyde de titane et d¿or a été développée. L¿utilisation de différentes méthodes de synthèse des nanoparticules a permis le contrôle de la morphologie et des propriétés physiques des films déposés par centrifugation. Finalement, l¿adéquation de ces films à leur utilisation en tant qu¿anode de cellules solaires à colorant a été évaluée.

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37

MIEDOUGE, MARCEL. "Apport du quantitative buffy coat test au diagnostic parasitologique du paludisme." Toulouse 3, 1993. http://www.theses.fr/1993TOU31702.

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38

Lindner, Johannes [Verfasser]. "On Continuous Magnetically Enhanced Centrifugation in Large Scale Downstream Processing of Bioproducts / Johannes Lindner." München : Verlag Dr. Hut, 2014. http://d-nb.info/1059329913/34.

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39

Delahaye, M. T. "An ultra scale-down study of recovery by centrifugation of human cells for therapy." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1396242/.

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The future success of the cell therapy sector depends largely upon the ability to produce large numbers of high quality and efficacious cells. Within the production of living cells, the product and process become inseparable, thus, the selection and implementation of a large scale commercial production process becomes crucial to the success of the therapy. Traditional cell therapy lifecycles from the discovery phase through to patient administration utilise various unit operations, necessary for expansion, primary recovery, purification and final formulation. It is the induction of variation within cell populations caused whilst processed within these processes that can potentially render the product ineffective and unusable, creating major concern within the healthcare sector. This body of work casts focus upon the recovery of human cells intended for therapeutic use by centrifugation and sediment resuspension, a commonly adopted process which facilitates primary recovery, cell washing and purification processes, as well as the concentration of cells to a final administration specification. With the creation of ultra scale-down techniques coupled with a Design of Experiments approach, the impact of key unit associated parameters such as centrifugation spin time and intensity, along with the technique adopted for sediment resuspension has been characterised for three different human cell lines intended for therapy. A potential developmental roadmap has been created for the production and evaluation of cells for therapies. A range of cell quality attributes were evaluated forming the characterisation criteria, encompassing the analysis of structural integrity, surface marker profiling, cell death induction, cell proliferation capacity, a change in cell size and morphology, the induction of cell signalling in the form of cytokine release and crucially, the potency of the therapy. This facilitated an indepth view into the response of cells when processed, exemplifying the somewhat robust capacity of human cells. This work has aided the formation of a mechanistic hypothesis concerning cell damage as a consequence of the process. Traditional centrifugation protocols operate at the lower extremes of the design space investigated, so characterisation can inform as to the limits of manufacturing at large scale. Critical process effects affecting the recovery of viable cells included (i) the cell preparation with long hold times leading to greater loss during centrifugation and (ii) the method of cell pellet resuspension with the use of few passes at high velocities resulting in greater loss than many passes at low velocity. The mechanisms behind these and other process induced damage are explored.

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40

Wearly, Douglas J. "Centrifugation and Rheology as Indicators of Long Term Stability of an Acidified Protein Matrix." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243978914.

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41

Tenambergen, Frederike [Verfasser]. "Development and characterization of parenteral fat emulsions prepared by dual asymmetric centrifugation / Frederike Tenambergen." Halle, 2017. http://d-nb.info/1149050225/34.

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42

Akin, Faith W., Stephanie M. Byrd, Owen D. Murnane, and A. Pearson. "The Effect of Age on the Subjective Visual Vertical During Bilateral and Unilateral Centrifugation." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/1887.

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43

Lopez, Isabelle. "« Développement d'un système universel de coulée d'alliages dentaires par centrifugation axiale à très haute vitesse sous vide secondaire »." Thesis, Reims, 2013. http://www.theses.fr/2013REIMO201.

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La fabrication de prothèses dentaires à base de titane a connu un réel essor ces dernières années. Cependant, la production de ces produits reste assez coûteuse, et le choix de producteurs est encore restreint. Les partenaires du projet de recherche Européen Den-ticast® ont identifié un fort potentiel pour la création d'une machine innovante, capable de produire ces pièces à un coût réduit et à un niveau de qualité élevé. Le projet est axé sur le domaine de la production de pièces de métal pour l'usage dentaire, avec comme objectif, le développement d'un nouveau système polyvalent de coulée des alliages, qui doit permettre de couler l'ensemble des alliages dentaires actuellement commercialisés (NiCr, CoCr), mais aussi le titane et ses alliages. Le prototype Denticast® associe, pour la première fois, la fusion par induction et l'injection par centrifugation à haute vitesse, sous vide secondaire. Entièrement programmable, cette machine doit pouvoir évoluer en fonction du développement de nouveaux alliages sur le marché dentaire.Ce projet réunit des partenaires européens de 3 pays différents (France, Allemagne, Italie) et 3 secteurs d'activité : industriel, académique et odontologique, de sorte que chacun ap-porte un aspect complémentaire au projet. Il comporte 3 phases principales : une phase d'étude, une phase de conception et une phase d'évaluation du prototype.Nos résultats montrent que Denticast® est capable de produire des pièces à usage dentaire de qualité, à grains fins et homogènes, avec un niveau de contrainte résiduelle relativement bas, et une fraction volumique de porosité faible. Les caractéristiques mécaniques sont globalement supérieures ou équivalentes aux systèmes commerciaux du marché Although the manufacture of titanium dental prostheses has experienced a real rise in the last years, the production of those products remains quite expensive, and the choice of pro-ducers is still limited. The partners of the European research project Denticast® have identi-fied a high potential for the creation of an innovative machine that can produce those dental parts at low cost and high quality level. The aim of this research is the development of a new, innovative and versatile system of casting alloys, which can cast all dental alloys (NiCr, CoCr) as well as titanium and its alloys. The prototype Denticast® associates for the first time the melting by induction and the injection by centrifugation with high speed under vacuum. Totally preset, this machine should be able to evolve according to the devel-opment of new dental materials.The project combines European partners from 3 different countries (France, Germany and Italy) and three sectors: industrial, academic and dental, so that each of them contributes to the project. It presents three main phases: a study phase, a phase of design and the evalua-tion phase of the prototype.Our results show that Denticast® is able to produce quality parts for dental use with a ho-mogeneous and fine grain, with a low level of residual stress and a relatively low volume of fraction porosity. In most cases, the mechanical characteristics are equal or even greater than other systems on the market at present

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44

Benakouche, Rabah. "Décision d'innovation : éléments pour une intégration des modèles ex post et ex ante." Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0340.

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Cette thèse relate la trajectoire du processus d'appropriation industrielle d'une innovation technologique. L'étude de cas est confrontée aux principales approches théoriques disponibles en la matière. L'objectif principal poursuivi consiste à détecter les logiques de traductions industrielles. Un des principaux résultats obtenus de cette recherche est présenté sous forme de modèle de simulation mathémathique.

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45

Miranda, de Carvalho Camila. "Génération in vitro et caractérisation immunophénotypique des cellules dendritiques canines obtenues à partir de monocytes." Lyon 1, 2004. http://www.theses.fr/2004LYO10208.

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Actuellement, les cellules dendritiques (DCs) sont très étudiées chez l'homme et chez la souris. Cependant, les travaux expérimentaux restent assez pauvre pour la majorité des autres espèces animales. Le chien présente des pathologies cancéreuses et auto-immunes spontanées comparables à celles de l'homme. De ce fait, il paraît être un bon modèle animal potentiel pour évaluer la validité de l'immunomodulation par l'intermédiaire des cellules dendritiques. Dans un premier temps, nous avons développé une méthode visant à purifier les monocytes canins. Dans ce travail, nous avons pu mettre au point une méthode de purification des monocytes canins en combinant une technique d'élutriation et d'immunopurification complémentaire par des billes magnétiques. Ensuite, nous avons produit et caractérisé des Mo-DCs en utilisant de l'IL-4 et du GM-CSF de chien. Nous avons établi que la molécule CD86 était un marqueur spécifique de ces cellules dans cette espèce. Ces cellules dendritiques canines sont très fortement stimulantes en MLR et expriment aussi de façon importante les molécules CMH de Classe II et le CD32. Le marquage spécifique CD86 permettra de mieux purifier et analyser les fonctions de ces cellules chez le chien. Ces travaux permettrons de mieux caractériser et produire des cellules dendritiques canines pour envisager leur utilisation en immunothérapie et ouvrir les perspectives de recherche thérapeutiques chez cette espèce

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46

Legrand-Buscema, Caroline. "Préparation de SrBi2Nb2O9 par voie sol-gel : cristallisation des poudres et couches minces épitaxiées." Limoges, 2000. http://www.theses.fr/2000LIMO0034.

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La tendance generale a la miniaturisation des dispositifs conduit de plus en plus a focaliser les recherches sur les materiaux fonctionnels en couches minces. Parmi ces materiaux, les ferroelectriques prennent une place de plus en plus importante notamment dans le domaine des memoires non volatiles. Si les pzt ont deja fait l'objet de nombreux travaux, les recherches sur les composes ferroelectriques a couches de bismuth ou phases d'aurivillius sont en plein essor en raison de leur resistance a la fatigue et de leur aptitude a conserver leur polarisation apres de nombreux cycles de fonctionnement. Dans le cadre general, et compte tenu de l'experience acquise au spcts dans ce domaine, le travail presente concerne une des phases d'aurivillius parmi les plus prometteuses, srbi 2nb 2o 9 (sbn), pour laquelle persistent encore des zones d'ombre concernant a la fois la fabrication, la nature des defauts structuraux, son epitaxie sur divers substrats monocristallins, ce dernier point etant etroitement lie a son utilisation dans les memoires (possibilite d'obtenir des couches ferroelectriques avec des orientations choisies de la polarisation par rapport au substrat). Sbn a ete prepare par voie sol-gel selon une technique deja utilisee au spcts. La cristallisation des xerogels, puis son orientation et l'epitaxie de couches deposees par centrifugation (spin-coating) ont ete etudiees a la fois par diffraction des rayons x et par microscopie electronique en transmission. La fabrication de la phase sbn cristallisee passe toujours par la formation d'une phase intermediaire de type fluorine de composition inconnue, certainement riche en bismuth, qui pourrait etre le precurseur des feuillets bi 2o 2 caracteristiques des phases d'aurivillius

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47

Chung, King Hei. "Three-dimensional centrifuge and numerical studies of multiple tunnel interaction /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20CHUNGK.

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Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2004. Includes bibliographical references (leaves 208-217). Also available in electronic version. Access restricted to campus users.

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48

Sienko, Kathleen Helen 1976. "Artificial gravity : adaptation of the vestibulo-ocular reflex to head movements during short-radius centrifugation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9237.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000. Also available online at the MIT Theses Online homepage <http://thesis.mit.edu>. Includes bibliographical references (p. 89-93). Short-radius centrifugation is currently being pursued as a potential countermeasure to long duration space flight. Short-radius centrifugation requires relatively high angular velocities (on the order of 30 rpm) to create centripetal accelerations on the order of 1 g. Unfortunately, out-of-plane head movements during centrifugation induce inappropriate vestibulo-ocular reflexes, debilitating motion sickness symptoms, and illusory tilt sensations due to conflicting visual and vestibular signals. Practical use of an intermittent short-radius centrifuge as a countermeasure requires that crew members be capable of rapidly adapting to the unexpected semicircular canal inputs with minimal side- or post-effects. Furthermore, adaptation not only has to be achieved, it also has to be appropriate for the environment (stationary, rotating, 1 g, or 0 g). The purpose of this research was to investigate humans' ability to attain and maintain adaptation to rotating environments. Subjects participated in a series of pre-/per-/and post-rotation data collection sessions consisting of both eye reflex recordings during head movements, a subjective battery of tests, and autonomic measurements. Eight subjects were tested on three days (D=1, 2, 8). Eye movements were measured in response to out-of-plane head movements during rotation at 23 rpm on-board the MIT short-radius centrifuge (r=2 m). Slow phase eye velocity (SPV) was reconstructed from filtered and de-saccaded eye movement data. The significant main effect of day and pre-/post-adaptation phase demonstrated that normalized SPV decreased following adaptation in the light. by Kathleen Helen Sienko. S.M.

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49

Lyne, Lisette Emma 1975. "Artificial gravity : evaluation of adaptation to head movements during short-radius centrifugation using subjective measures." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9250.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000. Also available online at the MIT Theses Online homepage <http://thesis.mit.edu>. Includes bibliographical references (p. 80-82). An experiment was performed to determine the ability of humans to adapt, and retain adaptation to out-of-plane head movements made during short-radius centrifugation. The hypothesis for the experiment was as follows: Repeated exposure to a series of yaw head movements made during short-radius centrifugation at 23rpm, (with the subject lying supine and the head on the axis of rotation) will result in a decrease in the magnitude of inappropriate perceived self-motion sensations and severity of motion sickness. Verbal accounts of perceived pitch, motion-sickness scores and computer animations of subjective sensations were obtained from eight subjects, during three sessions performed at the following intervals: day one, day two and day eight. Verbal accounts of perceived pitch obtained during rotation and post-experiment motion-sickness scores provide clear evidence of adaptation to the stimulus between days one and two, and some retention of adaptation to day eight. Computer animations of subjective sensations obtained after the experiment and motion-sickness scores reported during the experiment do not provide conclusive evidence of adaptation, or retention of adaptation. The validity of these techniques were explored, along with a qualitative analysis of the results. by Lisette Emma Lyne. S.M.

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50

Tajino, Junichi. "Intermittent application of hypergravity by centrifugation attenuates disruption of rat gait induced by 2 weeks of simulated microgravity." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202681.

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