Dissertations / Theses on the topic 'Laboratory models'
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1
Thomas, Ashwin Paul. "Simulated and laboratory models of aircraft sound transmission." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52319.
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With increased exposure to transportation noise, there have been continued efforts to help insulate homes from aircraft noise. Current aircraft noise guidelines are based primarily on outdoor sound levels. As people spend the majority of their time indoors, however, human perception is evidently more related to indoor sound levels. Investigations are being made to provide further insight into how typical residential constructions affect indoor response. A pilot study has built a single-room "test house", according to typical construction for mixed-humid climate regions, and has directly measured outdoor-to-indoor transmission of sound - with specific focus on continuous commercial aircraft signatures. The results of this study are being used to validate and improve modelling software that simulates a wide range of construction types and configurations for other US climate regions. The improved models will allow for increased flexibility in simulating the impacts of acoustic and energy retrofits. Overall, the project intends to improve the ability to predict acoustic performance for typical US construction types as well as for any possible design alterations for sound insulation.
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Mustow, R. E. "Aspects of dental plaque development in laboratory models." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379543.
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Bosak, Tanja Kirschvink Joseph L. "Laboratory models of microbial biosignatures in carbonate rocks /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-12102004-144939.
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Occhiogrosso, A. "Development of astrochemical models based on laboratory data." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1415490/.
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The more we discover about the molecular composition of the interstellar medium (ISM) the more we realise how difficult it is to reproduce the mechanisms behind this complex chemistry. To date, over 175 different molecular species have been detected in the ISM. Many of them are formed in the gas phase, but there is a growing number of species that form more efficiently on grain surfaces during the collapse of star-forming cores. An important issue in mimicking the interstellar medium chemistry is that there are few observational clues about the synthesis of complex organic molecules on grains; experimental work coupled with chemical modelling is therefore essential in order to understand the chemical complexity of the ISM. UCL_CHEM is a computer model that takes into account the gas-grain interactions occurring during this collapse, with the aim of reproducing the observed abundances of molecules in various astronomical environments. The work in this thesis deals with the coupling of UCL_CHEM with the most recent experimental results on the formation in the solid state of various complex organic molecules including methyl formate (see Chapter 3) and ethylene oxide and acetaldehyde (whose chemistry is extensively discussed in Chapters 4 and 5), all which have been the subject of recent astronomical interest. Moreover, important revisions of some reactions occurring in the gas phase have also been made. Despite everything seeming straightforward concerning the interstellar chemistry in the gas phase, there is still a great deal to unearth in this regard. Oxygen, for instance, is an important player in the ISM because it is the most abundant element after hydrogen and helium. Although its chemistry seems well understood, we propose a revised scheme for its reactions with small unsaturated hydrocarbons (see Chapter 6) and we show how the new reaction network affects the molecular abundances of these linear carbon chains. In Chapter 6, we also emphasise the relevance in treating structural isomers as two different species when they show peculiar chemical behaviours. Another key issue in reproducing the interstellar molecular variety concerns the freezeout of species onto dust grain surfaces. In particular, we know little about the constituents of the icy mantles. In Chapter 7, we analyse the case of sulfur-bearing species because the most dominant ice component is still debated.
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Firoozfar, Ali Reza. "Rock scour in hydraulic laboratory analog scour models." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1456.
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Erosional processes of solid materials have been the focus of many researchers around the world. Erosion can commence within a wide range of material strengths depending on the amount of water-driven energy and material properties. Erosion could also occur due to Aeolian effects as well as chemical weathering but these forcings are not of the focus of this research. Instead, the focus here is on rock erosion in waterways and in particular downstream of dams.
Rock erosion mostly takes place at the downstream of dams where the water conveys through the spillbays from upstream to the downstream during an extreme event. This phenomenon threatens both the structural soundness of the dam with implications to the public safety. It usually occurs when the applied hydrodynamic forces (average and fluctuating) exceed the strength of the rock mass formation. Rock scour at the downstream of dams due to high velocity impinging jet is a complex and highly dynamic process. So a deeper understanding of the process is crucial to determine the rock scour rate and extent.
Hydraulic laboratory models have been employed to investigate hydraulic processes and proved to be reliable tools for testing soil/sediment erosion; however, the study of rock scour remains challenging. The prototype rock formation cannot be utilized in the laboratory models because the flowing water in the scaled model contains much less energy and exerts less forcing. On the other hand, the use of granular sediment (non-cohesive), as a standalone approach to mimic the rock formation is not a precise method, since it will most probably lead to inaccurate results.
The idea of using a mixture of granular and cohesive sediment is investigated here to adequately simulate the rock erosion process in the laboratory scaled models. The granular sediment represents the rock blocks while the cohesive additive is a binder to keep the granular sediment together.
The rock scour process can occur through four mechanisms; fracture failure, block removal, fatigue failure and abrasion. In this study, because the focus is on the hydrodynamic forcing effects on rock erosion, we assume that in the completely and intermittently jointed rock, erosion is mostly governed by fracture, block removal and fatigue failure. Abrasion is triggered by collisional effects and is not the focus here. So, we hypothesize that if the rock formation considered being pre-fractured, it can be simulated using a mixture of non-cohesive sediment with cohesive additive.
This method was utilized to assess the rock scour process at the downstream of the Priest Rapids Dam. The Priest Rapids Dam project was part of a series of projects that was conducted at IIHR-Hydroscience & Engineering at The University of Iowa and sponsored by the Public Utility District No. 2 of Grant County, Ephrata, Washington (GCPUD) to investigate juvenile salmonid migration at the Wanapum/Priest Rapids Development. It is a hydroelectric, concrete gravity, and mid-elevation dam owned and operated by Public Utility District No. 2 of Grant County, Washington (the "District").
To aid the District in their evaluation of fish passage, IIHR-Hydroscience & Engineering constructed comprehensive three-dimensional physical models of the forebay and tailrace of Priest Rapids Dam and a third model of spillbays 19-22 and powerhouse Unit 1 (sectional model).
As part of the last phase of the project, it was crucial to assess the effects of the newly designed fish bypass system on the downstream rock foundation scour. To investigate this process, the 1:64 Froude-based scale tailrace model of the dam was utilized. The mixture of gravel, bentonite clay, and water was employed to mimic the rock formation and simulate the bedrock scour process in the model. Series of preliminary experiments were conducted to find the optimum mixture of gravel, bentonite and water to accurately replicate an existing scour hole observed in the prototype tailrace. Two scenarios were considered. First, tests were conducted to estimate the scour potential downstream of the fish bypass, which is currently under construction. Second, the scour potential downstream of the dam was also assessed for the Probable Maximum Flood (PMF) with the fish bypass system running. Based on the model tests results and observations, the simulated bedrock (mixture of gravel and cohesive bentonite) was able to replicate the rock scour mechanisms, i.e. fracture process, block removal and fatigue observed in nature. During the fish bypass scour tests, it was observed that the erosion process occurs in the form of block removal and fatigue failure.
During the PMF scour test, instead, it was observed that the mixture is eroded in chunks of substrate. This process can be representative of fracture failure in rock which occurs when the induced pressure fluctuation exceeds the fracture strength or equivalently toughness of the rock. In the preliminary phase of this work it was recognized that a prerequisite for replicating the processes in the laboratory is the proper preparation of the mixture. There is limited information available in the literature about how much cohesive additive is required to simulate the erosional strength of the prototype rock formation.
For this reason, in this study the effort has been made to develop a method to simulate the rock formation for studying rock scour process in the laboratory analog scaled models. To simulate the bedrock formation, various combination of granular sediment (gravel), cohesive additive, and water were created and tested. Choosing an appropriate cohesive additive concentration is critical and nearly a balancing act. An appropriate cohesive additive concentration should be cohesive enough to bind the material and not too strong to be eroded by the flowing water in the scaled models. Moreover, its properties should not change over time. Various cohesive additives can be mentioned i.e. kaolin clay, bentonite clay, cement, grease, paraffin wax. Among all of them, bentonite clay was chosen as the appropriate cohesive additive due to its swelling characteristic. When bentonite is mixed with granular sediment, it is restricted by the non-cohesive sediment grains. The bentonite expands to fill the voids and forms a tough, leathery mineral mastic through which water cannot readily move.
In order to assess the erodibility of the mixture the Jet Erosion Test (JET) apparatus was used. The JET apparatus is a vertical, submerged, circular, turbulent impinging jet which is widely accepted and utilized to assess cohesive soil erosion through flow impingement. There are devices such as flumes which could be effectively used for bank erosion where the flow shear action is prevalent. In this study, it was sought important that the forcing replicated in the experiments was of the same nature (normal impinging forcing instead of shear forcing) as observed in the downstream end of a dam. For this reason, JET was chosen as it provided a larger range of stresses (ranging between 100-1000 Pa) comparing to the flume device. The apparatus was designed based on the device developed by Hanson and Hunt (2007) and built at the IIHR-Hydroscience & Engineering.
Various replicate samples were made with different combinations of gravel, sodium bentonite clay, and water. To determine the erosional strength of the samples (critical stress) they were tested using the JET apparatus. The critical stress was determined as the stress associated with zero eroded mass. The results revealed that the erosional strength of the simulated bedrock mixtures highly depends on the amount of adhesive component (bentonite clay). The mixtures with the higher percentage of bentonite clay are less susceptible to erosion. The erosion threshold plot - similar to Annandale's plot - for the simulated bedrock mixtures was developed.
Using the erosional strength of the simulated bedrock mixtures, a step-by-step systematic method was developed to determine the optimum combination of weakly cohesive substrate in order to simulate the strength of the prototype bedrock. The method is based on the Annandale's erodibility index method and requires information about the prototype bedrock strength (erodibility index). The method is explained in conjunction with the Priest Rapids Dam project example.
The old trial and error method to establish an optimum weakly cohesive substrate is costly and time consuming especially in the case of large scale laboratory models. Also, the applicability of the method would be questionable when there is not enough information or a past data set that can be used as a baseline (witness) test. The new method eliminates these problems and the optimum mixture can be established using the geological information of the prototype bedrock formation.
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TETTAMANZI, MICHELE. "EXPECTATIONS IN MACROECONOMICS: PERSPECTIVES, LABORATORY EXPERIMENTS AND AB MODELS." Doctoral thesis, Università Cattolica del Sacro Cuore, 2017. http://hdl.handle.net/10280/36156.
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La presente tesi studia le aspettative in macroeconomia contribuendo alla letteratura esistente sia indagando circa il meccanismo di formazione delle aspettative, sia analizzando come le aspettative a razionalità limitata influenzino la dinamica economica.
Nel primo capitolo viene presentato un esperimento nel quale ai soggetti viene chiesto di predire il valore futuro dell'inflazione: a seconda del trattamento, i soggetti possono venire esposti ad un segnale, che mira a stabilizzare l'economia, che fungendo quindi da indicazione prospettica (Forward Guidance). I risultati vengono poi studiati sottolineando il meccanismo di formazione delle aspettative soprattutto in funzione della credibilità del segnale; inoltre viene studiata l'efficacia dello strumento di politica monetaria nella stabilizzazione del sistema economico: si evidenzia come un segnale informativo permetta una sensibile stabilizzazione dell'economia, prevenendo spirali deflazionistiche.
Nel secondo capitolo viene sviluppato un modello ad agenti il quale incorpora un meccanismo di formazione delle aspettative a razionalità limitata, derivato da esperimenti precedenti. Inoltre, grazie ad un peculiare processo di aggregazione, viene derivato un modello analiticamente trattabile che permette di studiare il meccanismo di trasmissione di uno shock, isolando gli effetti dovuti all'eterogeneità fra gli agenti e alle aspettative: entrambi gli effetti sono considerevoli ed aiutano nello spiegare la dinamica economica.The present dissertation analyses expectations in macroeconomics, contributing to the existing literature both studying the expectation formation process, and inquiring how economic dynamic is influenced by boundedly rational expectations. The first chapter presents a learn to forecast experiment in which subject are asked to form expectation regarding the future value of inflation: depending on the treatment, subjects might be exposed to a signal, which possibly aim at stabilizing economy, mimicking the non conventional monetary policy instrument called Delphic Forward Guidance. The collected data are studied trying to recover the underlying expectation formation process highlighting especially the role of credibility of the signal; moreover from the data emerges that informative Forward Guidance helps in stabilizing economy, drastically reducing the probability of deflationary spirals. The second chapter develops an agent-based model, encapsulating a boundedly rational expectation formation process, which had been extrapolated in previous experiments. Moreover benefiting from a specific aggregation procedure, we derive a model characterized by high analytical tractability, allowing hence to study the transmission mechanisms of a shock by insulating the effects due to the heterogeneity among agents and due to expectations: both the effects are sizable and help in understanding the dynamics of the economic system.
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Kiss, Andrew Elek. "Dynamics of laboratory models of the wind-driven ocean circulation." View thesis entry in Australian Digital Theses Program, 2000. http://thesis.anu.edu.au/public/adt-ANU20011018.115707/index.html.
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Kiss, Andrew Elek, and Andrew Kiss@anu edu au. "Dynamics of laboratory models of the wind-driven ocean circulation." The Australian National University. Research School of Earth Sciences, 2001. http://thesis.anu.edu.au./public/adt-ANU20011018.115707.
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This thesis presents a numerical exploration of the dynamics governing
rotating flow driven by a surface stress in the " sliced cylinder " model
of Pedlosky & Greenspan (1967) and Beardsley (1969), and its close
relative, the " sliced cone " model introduced by Griffiths & Veronis
(1997). The sliced cylinder model simulates the barotropic wind-driven
circulation in a circular basin with vertical sidewalls, using a depth
gradient to mimic the effects of a gradient in Coriolis parameter. In the
sliced cone the vertical sidewalls are replaced by an azimuthally uniform
slope around the perimeter of the basin to simulate a continental slope.
Since these models can be implemented in the laboratory, their dynamics
can be explored by a complementary interplay of analysis and numerical
and laboratory experiments. ¶
In this thesis a derivation is presented of a generalised
quasigeostrophic formulation which is valid for linear and moderately
nonlinear barotropic flows over large-amplitude topography on an f-plane,
yet retains the simplicity and conservation properties of the standard
quasigeostrophic vorticity equation (which is valid only for small depth
variations). This formulation is implemented in a numerical model based
on a code developed by Page (1982) and Becker & Page (1990). ¶
The accuracy of the formulation and its implementation are confirmed by
detailed comparisons with the laboratory sliced cylinder and sliced cone
results of Griffiths (Griffiths & Kiss, 1999) and Griffiths & Veronis
(1997), respectively. The numerical model is then used to provide insight
into the dynamics responsible for the observed laboratory flows. In the
linear limit the numerical model reveals shortcomings in the sliced cone
analysis by Griffiths & Veronis (1998) in the region where the slope and
interior join, and shows that the potential vorticity is dissipated in an
extended region at the bottom of the slope rather than a localised region
at the east as suggested by Griffiths & Veronis (1997, 1998). Welander's
thermal analogy (Welander, 1968) is used to explain the linear
circulation pattern, and demonstrates that the broadly distributed
potential vorticity dissipation is due to the closure of geostrophic
contours in this geometry. ¶
The numerical results also provide insight into features of the flow at
finite Rossby number. It is demonstrated that separation of the western
boundary current in the sliced cylinder is closely associated with a
" crisis " due to excessive potential vorticity dissipation in the viscous
sublayer, rather than insufficient dissipation in the outer western
boundary current as suggested by Holland & Lin (1975) and Pedlosky
(1987). The stability boundaries in both models are refined using the
numerical results, clarifying in particular the way in which the western
boundary current instability in the sliced cone disappears at large
Rossby and/or Ekman number. A flow regime is also revealed in the sliced
cylinder in which the boundary current separates without reversed flow,
consistent with the potential vorticity " crisis " mechanism. In addition
the location of the stability boundary is determined as a function of the
aspect ratio of the sliced cylinder, which demonstrates that the flow is
stabilised in narrow basins such as those used by Beardsley (1969, 1972,
1973) and Becker & Page (1990) relative to the much wider basin used by
Griffiths & Kiss (1999). ¶
Laboratory studies of the sliced cone by Griffiths & Veronis (1997)
showed that the flow became unstable only under anticyclonic forcing. It
is shown in this thesis that the contrast between flow under cyclonic and
anticyclonic forcing is due to the combined effects of the relative
vorticity and topography in determining the shape of the potential
vorticity contours. The vorticity at the bottom of the sidewall smooths
out the potential vorticity contours under cyclonic forcing, but distorts
them into highly contorted shapes under anticyclonic forcing. In
addition, the flow is dominated by inertial boundary layers under
cyclonic forcing and by standing Rossby waves under anticyclonic forcing
due to the differing flow direction relative to the direction of Rossby
wave phase propagation. The changes to the potential vorticity structure
under strong cyclonic forcing reduce the potential vorticity changes
experienced by fluid columns, and the flow approaches a steady free
inertial circulation. In contrast, the complexity of the flow structure
under anticyclonic forcing results in strong potential vorticity changes
and also leads to barotropic instability under strong forcing. ¶
The numerical results indicate that the instabilities in both models
arise through supercritical Hopf bifurcations. The two types of
instability observed by Griffiths & Veronis (1997) in the sliced cone are
shown to be related to the western boundary current instability and
" interior instability " identified by Meacham & Berloff (1997). The
western boundary current instability is trapped at the western side of
the interior because its northward phase speed exceeds that of the
fastest interior Rossby wave with the same meridional wavenumber, as
discussed by Ierley & Young (1991). ¶
Numerical experiments with different lateral boundary conditions are also
undertaken. These show that the flow in the sliced cylinder is
dramatically altered when the free-slip boundary condition is used
instead of the no-slip condition, as expected from the work of Blandford
(1971). There is no separated jet, because the flow cannot experience a
potential vorticity " crisis " with this boundary condition, so the western
boundary current overshoots and enters the interior from the east. In
contrast, the flow in the sliced cone is identical whether no-slip,
free-slip or super-slip boundary conditions are applied to the horizontal
flow at the top of the sloping sidewall, except in the immediate vicinity
of this region. This insensitivity results from the extremely strong
topographic steering near the edge of the basin due to the vanishing
depth, which demands a balance between wind forcing and Ekman pumping on
the upper slope, regardless of the lateral boundary condition. The
sensitivity to the lateral boundary condition is related to the
importance of lateral friction in the global vorticity balance. The
integrated vorticity must vanish under the no-slip condition, so in the
sliced cylinder the overall vorticity budget is dominated by lateral
viscosity and Ekman friction is negligible. Under the free-slip condition
the Ekman friction assumes a dominant role in the dissipation, leading to
a dramatic change in the flow structure. In contrast, the much larger
depth variation in the sliced cone leads to a global vorticity balance in
which Ekman friction is always dominant, regardless of the boundary
condition.
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Brown, Graham Alfred. "A study of bovine herpesvirus 1 pathogenesis using laboratory models." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304239.
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Siddall, Daniel Jonathan. "Patient specific spine models : the development of a laboratory validation spine." Thesis, University of Hull, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396751.
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Oates, Peter M. (Peter Michael) 1977. "Upscaling reactive transport in porous media : laboratory visualization and stochastic models." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39353.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references.
Solute transport models are essential tools for understanding and forecasting chemical concentrations in groundwater. Advection-dispersion based models can adequately predict spatial averages of conservative solute concentrations without using explicit maps of pore structures or variations in hydraulic conductivity. However, coupling advection-dispersion based transport models to chemical reaction models is inaccurate because it implicitly assumes complete mixing. Mixing in natural porous media is a slow process that can control the overall rate of chemical reactions, and the lack of mixing causes concentrations to be spatially variable. This thesis develops and experimentally validates a new solute transport modeling framework that approximates the correct amount of chemical reaction and provides concentration probability density functions, which are needed to address laws and regulations based on maximum contaminant levels. To study solute mixing and reaction in porous media, we conducted highly detailed lab-scale experiments by digitally imaging the movement of colored dye tracers and colorimetric chemical reactions through illuminated clear homogeneous and heterogeneous porous media.
(cont.) The resulting sequence of solute concentration maps demonstrates the problem of conventional solute transport models and shows that concentrations can be well approximated with Beta distributions. Conservative Beta distributions can be modeled with partial-differential equations for concentration mean and variance. These conservative distributions can then be transformed into joint reactant distributions, which produces product and remaining reactant distributions. This upscaling approach is verified by modeling the product and reactant means, variances, and distributions in heterogeneous media and product means in homogeneous media from our lab-scale experiments. We found that (co)variance production-destruction balances can approximate aqueous species covariance matrixes, which are necessary to form multivariate reactant distributions of complex reactive transport scenarios. Alternatively, these second moments can be used in upscaled reaction expressions derived from a second order Taylor series expansion. Incomplete mixing, parameterized by variance and covariance, causes an upscaled reaction rate to be almost an order of magnitude smaller compared to the conventional reaction rate that implicitly assumes complete mixing.
(cont.) Finally, manipulating the flow field to be perpendicular to its original direction would increase the rate of reactive mixing by an order of magnitude. Thus generating a transient flow field would be a practical way to accelerate natural attenuation and bioremediation.
by Peter M. Oates.
Ph.D.
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Westman, Gustaf. "Thermal cracking in high performance concrete : viscoelastic models and laboratory tests." Licentiate thesis, Luleå tekniska universitet, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25652.
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Emborg, Mats. "Temperature stresses in massive concrete structures : viscoelastic models and laboratory tests." Licentiate thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 1985. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25973.
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Sevcik, Jaroslav. "Program transformations in weak memory models." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3132.
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We analyse the validity of common optimisations on multi-threaded programs in two memory models—the DRF guarantee and the Java Memory Model. Unlike in the single-threaded world, even simple program transformations, such as common subexpression elimination, can introduce new behaviours in shared-memory multi-threading with an interleaved semantics. To validate such optimisations, most current programming languages define weaker semantics, called memory models, that aim to allow such transformations while providing reasonable guarantees. In this thesis, we consider common program transformations and analyse their safety in the two most widely used language memory models: (i) the DRF guarantee, which promises sequentially consistent behaviours for data race free programs, and (ii) the Java Memory Model, which is the semantics of multithreaded Java. The DRF guarantee is the semantics of Ada and it has been proposed as the semantics of the upcoming revision of C++. Our key results are: (i) we prove that a large class of elimination and reordering transformations satisfies the DRF guarantee; (ii) we find that the Java language is more restrictive—despite the claims in the specification, the Java Memory Model does not allow some important program transformations, such as common subexpression elimination. To establish the safety results, we develop a trace semantic framework and describe important program optimisations as relations on sets of traces. We prove that all our elimination and reordering transformations satisfy the DRF guarantee, i.e., the semantic transformations cannot introduce new behaviours for data race free programs. Moreover, we prove that all the transformations preserve data race freedom. This ensures safety of transformations composed from eliminations and reorderings. In addition to the DRF guarantee, we prove that for arbitrary programs, our transformations prevent values appearing “outof- thin-air”—if a program does not contain constant c and does not perform any operation that could create c, then no transformation of the program can output c. We give an application of the semantic framework to a concrete language and prove safety of several simple syntactic transformations. We employ similar semantic techniques to prove validity of several classes of transformations, such as the elimination of an overwritten write or reordering of independent memory accesses, in the Java Memory Model. To establish the iii negative results for the Java Memory Model, we provide counterexamples showing that several common optimisations can introduce new behaviours and thus are not safe.
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Wells, Judith R. (Judith Roberta). "A laboratory study of localized boundary mixing in a rotating stratified fluid." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/58062.
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Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and the Woods Hole Oceanographic Institution), 2003.Includes bibliographical references (p. 145-148).
Oceanic observations indicate that abyssal mixing is localized in regions of rough topography. How locally mixed fluid interacts with the ambient fluid is an open question. Laboratory experiments explore the interaction of mechanically induced boundary mixing and an interior body of linearly stratified rotating fluid. Turbulence is generated by a vertically oscillating horizontal bar, located at middepth along the tank wall. The turbulence forms a region of mixed fluid which quickly reaches a steady state height and collapses into the interior. The mixed layer thickness ... is independent of the Coriolis frequency f. N is the buoyancy frequency, co is the bar frequency, and the constant, Y=1 cm, is empirically determined by bar mechanics. In initial experiments, the bar is exposed on three sides. Mixed fluid intrudes directly into the interior as a radial front of uniform height, rather than as a boundary current. Mixed fluid volume grows linearly with time ... The circulation patterns suggest a model of unmixed fluid being laterally entrained with velocity, e Nhm, into the sides of a turbulent zone with height hm and width Lf ... where Lf is an equilibrium scale associated with rotational control of bar-generated turbulence. In accord with the model, outflux is constant, independent of stratification and restricted by rotation ... Later experiments investigate the role of lateral entrainment by confining the sides of the mixing bar between two walls, forming a channel open to the basin at one end. A small percentage of exported fluid enters a boundary current, but the bulk forms a cyclonic circulation in front of the bar. As the recirculation region expands to fill the channel, it restricts horizontal entrainment into the turbulent zone. The flux of mixed fluid decays with time.
(cont.) ... The production of mixed fluid depends on the size of the mixing zone as well as on the balance between turbulence, rotation and stratification. As horizontal entrainment is shut down, longterm production of mixed fluid may be determined through much weaker vertical entrainment. Ultimately, the export of mixed fluid from the channel is restricted to the weak boundary current.
by Judith R. Wells.
Ph.D.
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Kirstein, Frank. "Investigations of immune responses in different mouse models of allergic asthma." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/3171.
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Bayoumi, Ahmed M. "New laboratory test procedure for the enhanced calibration of constitutive mode." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03292006-114517/.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Paul Mayne, Committee Member ; James Tsai, Committee Member ; Glenn Rix, Committee Member ; David Frost, Committee Member ; Carlos Santamarina, Committee Chair.
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Wojtczak, Dominik. "Recursive probabilistic models : efficient analysis and implementation." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3217.
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This thesis examines Recursive Markov Chains (RMCs), their natural extensions and connection to other models. RMCs can model in a natural way probabilistic procedural programs and other systems that involve recursion and probability. An RMC is a set of ordinary finite state Markov Chains that are allowed to call each other recursively and it describes a potentially infinite, but countable, state ordinary Markov Chain. RMCs generalize in a precise sense several well studied probabilistic models in other domains such as natural language processing (Stochastic Context-Free Grammars), population dynamics (Multi-Type Branching Processes) and in queueing theory (Quasi-Birth-Death processes (QBDs)). In addition, RMCs can be extended to a controlled version called Recursive Markov Decision Processes (RMDPs) and also a game version referred to as Recursive (Simple) Stochastic Games (RSSGs). For analyzing RMCs, RMDPs, RSSGs we devised highly optimized numerical algorithms and implemented them in a tool called PReMo (Probabilistic Recursive Models analyzer). PReMo allows computation of the termination probability and expected termination time of RMCs and QBDs, and a restricted subset of RMDPs and RSSGs. The input models are described by the user in specifically designed simple input languages. Furthermore, in order to analyze the worst and best expected running time of probabilistic recursive programs we study models of RMDPs and RSSGs with positive rewards assigned to each of their transitions and provide new complexity upper and lower bounds of their analysis. We also establish some new connections between our models and models studied in queueing theory. Specifically, we show that (discrete time) QBDs can be described as a special subclass of RMCs and Tree-like QBDs, which are a generalization of QBDs, are equivalent to RMCs in a precise sense. We also prove that for a given QBD we can compute (in the unit cost RAM model) an approximation of its termination probabilities within i bits of precision in time polynomial in the size of the QBD and linear in i. Specifically, we show that we can do this using a decomposed Newton’s method.
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Tillett, David McIlvain. "Lipid productivity and species competition in laboratory models of algal mass cultures." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10274.
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Bradley, Belinda Fay. "The effects of Lavandula angustifolia on animal and human laboratory models of anxiety." Thesis, University of Central Lancashire, 2008. http://clok.uclan.ac.uk/11970/.
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Lavender (Lavandula angustifolia) is a popular treatment for stress and mild anxiety. Currently, there are few reliable investigations of its efficacy because cognitive and associative effects of odours can confound pharmacological effects. Some of these problems can be overcome by testing the effects of odours in animals, and by using orally-administered lavender in sealed capsules in human participants. In addition, a criticism of current studies is that most employ short-term administration of lavender, even though humans most often use lavender over longer time-periods. There are two parts to this thesis. The first part addressed two questions; whether lavender odour exhibits anxiolytic effects in animal models of anxiety, and whether chronically administered lavender is more effective than acutely administered lavender. The second part addressed the question of whether, in a randomised double-blind placebo-controlled trial, orally-administered lavender exhibits anxiolytic effects in humans. This thesis makes three significant contributions: First, these studies provided a validation of the gerbil elevated plus-maze model of anxiety in both male and female gerbils, a model that has only previously been validated in female gerbils (Varty et al., 2002). Second, the studies on gerbils have shown that both lavender and rose essential oils have anxiolytic effects, which, rather than dissipating following acute odour administration (Cooke & Ernst, 2000), potentiate over time. Lavender’s effects were particularly apparent in female gerbils on measures related to risk-assessment, a behaviour that has been related to the human anxiety trait of worry (Blanchard, Blanchard, Griebel, & Nutt, 2008). Third, lavender had a clear dose response effect in reducing baseline anxiety in humans when tested acutely via oral administration, although there were no effects when more severe anxiety was induced. The route of administration and the fact that iv lavender had dose response effects indicate that lavender’s effects are not caused by psychological qualities of the odour, but are more likely to be due to direct pharmacological effects. Again, and comparable to results in gerbils, lavender’s anxiolytic effects in human females were more noticeable, particularly during the anxiety task and in the recovery phase of the study. In summary, prolonged exposure to lavender odour relieved anxiety in a validated animal model of anxiety, and orally-administered lavender alleviated mild anxiety in humans. In both cases, results were more prevalent in females.
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Tan, Ju Chiat Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Investigation of abnormal cardiac function in murine models of hypocontractility and hypercontractility." Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2006. http://handle.unsw.edu.au/1959.4/28879.
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Heart failure has a significant impact on mortality and morbidity. Dilated cardiomyopathy (DCM) is the third most common cause of heart failure and the most common reason for heart transplantation. Familial DCM is known to be caused by mutations in the LMNA gene encoding lamins A and C. New methods to enhance cardiac contractility would be beneficial in the treatment or prevention of heart failure. The focus of this thesis was to evaluate the mechanisms of altered contractility in two mouse models: the LMNA knockout model (homozygous, Lmna-/-; heterozygous, Lmna+/-) generated by targeted deletion of the lmna gene, and the model of enhanced contractility due to cardiac alpha1A-adrenergic receptor (???1A-AR) overexpression (A1A1). Previous studies have found altered nuclear-desmin connections in lamin A/C deficient mice. It was proposed that these alterations result in ???defective force transmission???, which leads to DCM. Studies in this thesis have supported this hypothesis. Studies of isolated single cardiomyocytes from mice aged 4-6 weeks demonstrated abnormal cell morphology and contractile dysfunction in Lmna-/- cardiomyocytes, while Lmna+/- cells showed no overt phenotype. Excitation-contraction coupling experiments and forcecalcium studies in skinned fibers excluded altered calcium kinetics as a primary cause of DCM in this model, but there was evidence of reduced sarcomere numbers and reduced sarcomere lengths as a contributor to reduce force generation in Lmna-/- and Lmna+/- mice. Previous in vivo studies showed that A1A1 mice had enhanced contractility with the absence of hypertrophy. Studies on isolated single cardiomyocytes from A1A1 mice aged 8-12 weeks showed reduced contractility in the absence of ???1A-AR stimulation, but an exaggerated response to ???1A-AR stimulation. In contrast isolated isovolumic Langendorff perfused A1A1 hearts without ???1A-AR stimulation replicated the enhanced contractility observed in vivo. These studies are consistent with down-regulation of contractility due to the hyperactivity of the overexpressed ???1A-AR in vivo, which only becomes evident in isolated cells without ???1A-AR stimulation due to the loss of functional receptor numbers during isolation. Sufficient spontaneously active ???1A-ARs are preserved in the isolated Langendorff heart preparation to ensure maximum contractility driven by increase calcium release.
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Ng, Kwok-chai Kelvin, and 吳國際. "Local and systemic effects of hepatic radiofrequency ablation in animal models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29434920.
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Pham, Minh Tuan. "Etudes des mécanismes de transfert de charge dans les plateformes granulaires renforcées par géosynthétiques." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI025/document.
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L’aménagement progressif du territoire conduit à l’exploitation de nouvelles zones, actuellement délaissées, car présentant des risques pour la sécurité des usagers. C’est notamment le cas des zones d’effondrements potentiels qui sont liées à la présence de cavités souterraines. Parmi les nombreuses solutions préventives, le renforcement géosynthétique permet de prévenir les risques d’effondrement localisés. Cette solution de renforcement est largement utilisée à la fois pour ses avantages économiques et environnementaux, que pour sa facilité et rapidité de mise en œuvre. Néanmoins, les méthodes de conception existantes des plateformes granulaires renforcées par géosynthétiques sont fondées sur diverses hypothèses simplificatrice et ne prennent pas en compte toute la complexité du problème. En effet, ces méthodes ne considèrent pas par exemple l’influence du mode d’ouverture de la cavité, le foisonnement du sol granulaire au droit de la cavité ou encore la distribution de charge sur le géosynthétique après ouverture de la cavité.La présente étude tente d’améliorer les méthodes de dimensionnement en analysant les mécanismes développés dans la plateforme granulaire renforcée sur la base d’une campagne expérimentale couplée à des modélisations numériques.Un dispositif expérimental a été développé pour simuler l’ouverture d’une cavité sous une plateforme renforcée par géosynthétique. Ce dispositif permet de simuler deux modes d’ouverture : une trappe qui s’abaisse ou une ouverture concentrique, pour différentes hauteurs de plateformes. Les mécanismes de renforcement sont étudiés en mesurant la déflexion du géosynthétique, le tassement en surface et la distribution de contrainte verticale qui s’applique du le géosynthétique. Un modèle numérique par éléments finis a été calibré sur les résultats expérimentaux puis utilisé pour analyser finement les mécanismes pour de nombreuses configurations.Cette étude expérimentale et numérique a permis d’améliorer la compréhension des mécanismes de transfert de charge et de foisonnement dans la zone effondrée et de valider expérimentalement l’influence du mode d’ouverture sur les mécanismes. Sur la base de ces résultats, des propositions sont formulées pour améliorer le dimensionnement des plateformes renforcées par géosynthétiques soumises à des effondrements localisésThe progressive development of the territory leads to the exploitation of new areas, which are currently being abandoned because they come up risks to the safety of users. This is particularly the case for areas of potential collapse that are related to the presence of underground cavities. Among the many preventative solutions, geosynthetic reinforcement prevents localized collapse. This solution is widely used for both its economic and environmental benefits, as well as for its ease and speed of setting up. However, the existing design methods for granular platforms reinforced by geosynthetic are based on various simplifying assumptions and do not take the complexity of the problem into account. These methods do not consider, for example, the influence of how the cavity is opened, the expansion of granular soil above the cavity, or the stress distribution on the geosynthetic after opening the cavity.The present study tries to improve the design methods by analyzing mechanisms developed inside the reinforced granular platform on the basis of an experimental study coupled with numerical simulations.An experimental device was developed to simulate the opening of a cavity under a platform reinforced by geosynthetic. This device allows simulating two types of opening: a trapdoor or a concentric opening, for various heights of platforms. The mechanisms are studied by measuring the deflection of the geosynthetic, the settlement at the surface and the stress distribution applied of the geosynthetic. A finite element model was calibrated on the experimental results then used to analyze mechanisms finely for many configurations.This experimental and numerical study allows improving the understanding of the stress distribution, the soil expansion above the cavity and experimentally validated the influence of the opening mode on the mechanisms. Based on these results, proposals are formulated to improve the design of geosynthetic-reinforced platforms subject to localized collapse
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Di, Giuseppe Erika. "Dynamics of subduction and implications for plate kinematics : insights from numerical and laboratory models /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17833.
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Maconochie, Alasdair James. "The development of laboratory test facilities to capture acoustic signatures from sediment bed models." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/644.
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Long, Maureen Devaney. "Anisotropy and deformation in the Earth's mantle : seismological observations, geodynamical models, and laboratory experiments." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37360.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
"June 2006."
Includes bibliographical references (p. 289-316).
In this thesis I report the results of several studies of elastic anisotropy and deformation in the Earth's mantle, using shear wave splitting measurements, numerical models of geodynamical processes, and laboratory experiments on mantle minerals. I evaluate the performance of several methods for measuring shear wave splitting at broadband stations, and discuss how different measurements can inform our interpretation of mantle anisotropy. I describe a set of shear wave splitting measurements from both teleseismic and local earthquakes at 65 stations of the F-net array in Japan. I find considerable evidence from the measured splitting patterns for complex and heterogeneous anisotropy beneath Japan associated with the subduction of the Pacific and Philippine Sea plates beneath Eurasia. The comparison of teleseismic and local splitting at stations in southwestern Japan provides strong evidence for trench-parallel anisotropy in the mantle wedge above the subducting slab. I consider several scenarios that would produce the observed anisotropy and conclude that the most likely model for deformation beneath the Ryukyu arc is corner flow in the mantle wedge, with a region extending ~ 150 kilometers from the trench dominated by B-type olivine fabric.
(cont.) To characterize further the detailed pattern of flow and anisotropy, I evaluate a series of two-dimensional finite element models that describe the subduction of the Philippine Sea plate beneath southwestern Japan, and compare the resulting flow field, strain, and anisotropy in the mantle wedge to F-net shear wave splitting observations. To complement this forward modeling approach, I develop and implement a method for the 2.5-D inversion of shear wave splitting intensity measurements for anisotropic structure in the upper mantle. I present preliminary anisotropic models for southwestern Japan and discuss strategies for explicitly integrating the tomographic inversion of splitting intensity data with numerical models that describe geodynamic processes in the wedge. Finally, I describe a series of laboratory experiments characterizing deformation and the resulting lattice preferred orientation in magnesiowüstite, a lower mantle mineral, and discuss the implications for the interpretation of seismic anisotropy at the base of the mantle.
by Maureen Devaney Long.
Ph.D.
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Grigg, Nicola Jane, and nicky grigg@csiro au. "Benthic Bulldozers and Pumps: Laboratory and Modelling Studies of Bioturbation and Bioirrigation." The Australian National University. Centre for Resource and Environmental Studies, 2003. http://thesis.anu.edu.au./public/adt-ANU20060228.104425.
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Aquatic sediments are the recipients of a continual rain of organic debris from the water column. The decomposition reactions within the sediment and the rates of material exchange between the sediment and water column are critically moderated by the transport processes within the sediment. The sediment and solute movement induced by burrowing animals bioturbation and bioirrigation far exceed abiotic transport processes such as sedimentation burial and molecular diffusion. Thalassinidean shrimp are particularly abundant burrowing animals. Living in high density populations along coastlines around the world, these shrimp build complex burrow networks which they actively maintain and irrigate.¶
I used a laser scanner to map thalassinidean shrimp (Trypaea australiensis) mound formation. These experiments measured rapid two-way exchange between the sediment and depth. Subduction from the sediment surface proved to be just as important as sediment expulsion from depth, yet this is not detected by conventional direct entrapment techniques. The experiments demonstrated that a daily sampling frequency was needed to capture the extent of the two-way exchange.¶
I derived a one-dimensional non-local model accounting for the excavation, infill and collapse (EIC) of burrows. Maximum likelihood analyses were used to test the model against 210Pb and 228Th profiles taken from sediment cores in Port Phillip Bay, Melbourne. The maximum likelihood approach proved to be a useful technique for quantifying parameter confidence bounds and allowing formal comparison with a comparable biodiffusion model. The EIC model generally outperformed the biodiffusion model, and in all cases best EIC model parameter estimates required some level of burrow infill with surface material. The EIC model was expanded to two and three dimensions, which allowed the representation of lateral heterogeneity resulting from the excavation, infill and collapse of burrow structures. A synthetic dataset generated by the two-dimensional model was used to demonstrate the effects of heterogeneity and core sampling on the mixing information that can be extracted from one-dimensional sediment core data.¶
Burrow irrigation brings oxygenated water into burrow depths, and can affect the nitrogen cycle by increasing the rates of coupled nitrification and denitrification reactions. I modelled the nitrogen chemistry in the annulus of sediment surrounding an irrigated burrow using a radially-symmetrical diffusion model. The model was applied to three published case studies involving thalassinidean shrimp experiments and to field data from Port Phillip Bay. The results highlighted divergences between current theoretical understanding and laboratory and field measurements. The model further demonstrated potential limitations of measurements of burrow characteristics and animal behaviour in narrow laboratory tanks. Activities of burrowing animals had been hypothesised to contribute to high denitrification rates within Port Phillip Bay. Modelling work in this thesis suggests that the model burrow density required to explain these high denitrification rates is not consistent with the sampled density of thalassinidean shrimp in the Bay, although dense burrows of other animals are likely to be important. Limitations of one-dimensional representations of nitrogen diagenesis were explored via comparisons between one-dimensional models and the full cylinder model.
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Manandhar, Chandra Bahadur. "Rapid estimation of lives of deficient superpave mixes and laboratory-based accelerated mix testing models." Diss., Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3868.
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Leland, Matthew. "Using Analogical Models in Undergraduate Chemistry Laboratory Courses to Improve Student Understanding of Beer's Law." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/LelandM2006.pdf.
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Antle, David. "The use of laboratory and participatory ergonomic research models to investigate working posture in industry." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121371.
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Consensus on physical mechanisms linking work posture to discomfort and disorder risk has not been reached. The objective of this dissertation was to use a series of laboratory studies to identify measurements associated with discomfort and disorder risk in lower limb, back and neck/shoulder regions, and assess how these measurement outcomes differ between standing, seated and sit-standing postures. Participatory intervention methods were also used to investigate workplace factors that impact on posture selection and rotation. In the core set of investigations, healthy participants performed an industrially-modelled box-folding task over three 34-minute sessions in standing, seated and sit-standing postures (developed using a novel foot stand) while lower limb vascular parameters, trunk and upper limb muscular parameters, postural kinetics and discomfort were measured. Links between discomfort in various body regions and changes in the vascular, muscular and kinetic outcomes were investigated within and between postures. Investigation at a partner enterprise was conducted using 'participatory ergonomics' investigation methods and establishment of an "Ergonomics Team". Results show that during standing work, increases in blood volume and postural sway are associated with lower limb discomfort, and initially higher levels of shared activation between bilateral hip musculature are associated with higher levels of back discomfort. In comparison to standing, seated work leads to improved lower limb vascular and discomfort outcomes, but increases muscular demands and discomfort in the back and neck/shoulder regions. Also in comparison to standing, the sit-standing posture led to improved lower limb outcomes, with no significant differences in back and neck/shoulder outcomes. Together, findings reveal that each posture has positive and negative consequences. Data suggests that frequent (15-20min) rotation between postures may prevent onset of unwanted effects. Meanwhile, early investigations at the workplace revealed key policy, work organization and design issues that influenced the choice of appropriate laboratory methods and may affect knowledge uptake related to posture selection and rotation in the plant. As such, an integrated, participatory ergonomics approach may be optimal in ensuring that relevant laboratory methods are developed to produce usable knowledge for the workplace, and key knowledge translation strategies are in place for dissemination back to the workplace.Les mécanismes reliant la posture de travail à l'inconfort et au risque de maladie ne sont toujours pas bien compris. L'objectif de cette dissertation était d'utiliser une série d'études de laboratoires afin d'identifier ces mécanismes pour les régions des membres inférieurs, du dos et des membres supérieurs, et d'évaluer comment ces mesures diffèrent entre les postures debout, assis, et assis-debout. Des méthodes d'intervention participative ont aussi été utilisées afin d'investiguer les facteurs de travail ayant un impact sur la sélection et la rotation des postures.Dans la majorité des investigations, des participants en santé ont effectué une tâche de pliage de boites modélisée d'après l'industrie durant trois séances de 34 minutes en posture debout, assis et assis-debout (à l'aide d'un support de pieds nouvellement développé) alors qu'étaient enregistrés des paramètres vasculaires aux membres inférieurs, des paramètres musculaires à la colonne et au membre supérieur, la cinétique de posture et l'inconfort. Des liens entre l'inconfort à diverses régions corporelles et les changements des mesures vasculaires, musculaires et cinétiques ont été évalués pour chaque posture et entre elles. Une investigation à une entreprise partenaire a été effectuée en utilisant des méthodes d'ergonomie participative et en établissant une 'Équipe Ergo'. Les résultats démontrent que durant le travail debout, des augmentations de volume sanguin et d'oscillation de la posture étaient associés à l'inconfort au membre inférieur, et une élévation initiale des niveaux d'activation mutuelle entre la musculature bilatérale des hanches était associée à des niveaux plus élevés d'inconfort du dos. En comparaison à la posture debout, la posture assis-debout a mené à des améliorations des mesures du membre inférieur, sans différences significatives des mesures du dos et de la région cou-épaules. Ensemble, ces résultats démontrent que chaque posture a des effets positifs et négatifs. Les données suggèrent qu'une rotation fréquente (15-20min) entre les postures pourrait prévenir l'apparition d'effets indésirables. Par ailleurs, les investigations préliminaires en entreprise ont révélé des aspects-clés de nature politiques, d'organisation du travail et de design qui ont influencé le choix des méthodes de laboratoire appropriées et qui pourront influencer l'utilisation des connaissances en lien avec le choix et la rotation des postures à l'usine. De surcroit, une approche intégrée d'ergonomie participative serait optimale pour assurer le développement de méthodes de laboratoire pertinentes afin de produire des connaissances applicables en milieu de travail et d'implanter des stratégies de courtage de connaissances pour la dissémination en milieu de travail.
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Tian, Li, and 田理. "Toxicological effects and mechanisms of selected foodborne toxins in medaka and zebrafish models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/197111.
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Foodborne toxins include a variety of biologically produced toxins and process-induced toxicants. Among them, marine algal toxins in polluted seafood can induce serious harmful effects on human, while heat-induced toxicants remain in a wide range of food and chronically affect health. In this present study, several representative toxins from these two categories were selected and studied, they are, brevetoxins (PbTxs), saxitoxin (STX) and acrolein (ACR). During past decades, the molecular actions of these toxins have been well studied, however, their effects and mechanisms corresponding to their sublethal toxicity in vivo still need more investigation. Therefore, in our current study, we adopted medaka fish (Oryzias melastigma) and zebrafish (Danio rerio) as models to study the toxicological responses and pathways of these selected toxins at the molecular and cellular level.
In the first part of study, the targeted organs of medaka fish, gills and brains, were studied in medaka fish after exposure to the sublethal level of PbTx-1, the most potent neurotic shellfish poisoning (NSP) toxin. Facilitated by the two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ ionization tandem time-of-flight mass spectrometry (MALDI TOF/TOF MS), proteins affected by PbTx-1 in these organs were identified, including myosin like proteins, aldose reductase, gelsolin and keratin. Collectively, the proteins altered after exposure suggested the altered calcium ion binding process, and dysfunction in cytoskeleton assembly and metabolism.
After successfully applying the fish model and proteomic approaches in the NSP toxin study, we put emphasis on the developmental toxicity of foodborne toxins, as children are more sensitive and vulnerable to foodborne toxins. Among the marine algal toxins, paralytic shellfish poisoning (PSP) toxins are the commonest and most lethal ones with STX as the most potent PSP toxin. Therefore, we examined the developmental effects of STX using medaka model. By exposing medaka embryos from the early blastula stage onwards, which covered the main developmental stage of the central nervous system and somites, we found newly hatched medaka fish exhibit abnormal growth with longer body length and relatively smaller yolk sac size. High cell proliferation, neuron development, and metabolism were confirmed by whole-mount immunostaining and 2-DE. In summary, STX disturbs the normal growth of medaka embryos probably by affecting the metabolic rate in the exposed medaka embryos.
Opposite to STX, after exposure to ACR, a pollutant that ubiquitously exists in food and environment, the zebrafish exhibited delayed development. ACR is a known glutathione (GSH) depleting factor and oxidative stress inducer. Apart from developmental retardance, increased reactive oxygen species (ROS) and inflammation were found in newly hatched zebrafish, suggesting the developmental delay may be partly related to the ACR-induced oxidative stress.
In summary, findings from the present study highlighted the molecular responses and possible pathways of some selected foodborne toxins. Developmental effects and toxicity were also found after exposing to both the biologically produced toxin and the heat-produced toxicant. Our current study makes contributions to the knowledge on the hazardous effects of foodborne toxins in vivo, and provides useful information for the further study on the human health.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Evans, Timothy J. "Selected aspects of the toxicokinetics of cadmium and lead in animal and cellular models /." Fulltext PDF download Free to MU Campus, others may purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074398.
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Howett, Carly Jacqueline Amy. "Laboratory measurements of ammonia ice and ammonium hydrosulphide ice for use in Jovian radiative transfer models." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437054.
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Tang, C. K. K. "Performance studies of a thyristor controlled reactor for arc furnace compensation using computer and laboratory models." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381290.
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Kimura, Yosuke. "Release kinetics of organic chemicals from contaminated site soils : laboratory measurement and applicability test of models /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Hartunians, Jordan. "High temperature H2 bio-production in Thermococcales models : setting up bases optimized high pressure solutions." Thesis, Brest, 2020. http://www.theses.fr/2020BRES0033.
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L’H2, vecteur d’énergie prometteur, peut être synthétisé par les Thermococcales. La haute pression (HP) influencerait le métabolisme associé, mais n’a pas été envisagée en pratique. Après criblage d’isolats pour dégradations de substrats et productions d’H2, T. barophilus MPT, croissant préférentiellement à 40 MPa, a été choisi comme modèle, et sa fermentation a été décrite dans un contexte appliqué. Des méthodes HP ont été optimisées pour étudier l’H2. Un bioréacteur de 400mL de culture continue a été amélioré, maintenant des fluides corrosifs à HP hydrostatique (jusqu’à 120 MPa) et gazeuse (jusqu’à 40 MPa) jusqu’à 150 °C. Il a permis de mesurer la production d’H2 de notre souche à HP gazeuse. Un tube compressible pour culture discontinue à phase gaz étanche a été inventé, et a servi à mesurer la production d’H2 de T. barophilus en HP hydrostatique. Le métabolisme HP de la souche a été étudié grâce à des délétions préalables de gènes clés (mbh, mbs, co-mbh, shI, shII). Les rôles des enzymes liées ont été précisés via des mesures de croissances, produits (H2, H2S, acétate) et expressions génétiques des mutants, à 0,1 et 40 MPa. La tolérance à l’H2 de T. barophilus a été augmentée par évolution adaptative en laboratoire.« Evol », la souche fille acclimatée durant 76 générations à une saturation d’H2, a crû dans 10% d’H2, contrairement à la souche mère. Pour comprendre ces adaptations, les produits (H2, H2S, acétate), transcriptomes et génomes des deux souches ont été comparés. Avec 119 mutations génomiques, le métabolisme de l’H2 a été modifié dans le variant. Ce projet souligne l’intérêt du caractère piézophile des Thermococcales dans la bio-production d’H2 et permet de proposer des stratégies d’H2 et permet de proposer des stratégies d’optimisationH2, a promising energetic vector, can be synthesized by Thermococcales. High pressure (HP) could influence the associated metabolism, but was not practically considered. After having screened isolates for assets in substrate degradation and H2 yields, T. barophilus MPT, growing optimally at 40 MPa, was chosen as a model and its metabolism was characterized in an applied context. Methods for HP culture were optimized for H2 studies. Our HP bioreactor for continuous culture underwent major improvements. This 400 mL container, able to maintain corrosive fluids at hydrostatic (up to 120 MPa) and gas (up to 40 MPa) pressures, at up to 150 °C, served to assess H2 production of our strain at high gas pressure. We also created a compressible device for discontinuous leak-free gas-phase incubations, allowing to measure T. barophilus HP H2 production (hydrostatic). HP adaptations of T. barophilus were observed thanks to previous deletions of key genes (mbh, mbs, co-mbh, shI, shII).We refined the roles of each concerned enzyme by assessing growths, end-products (H2, H2S, acetate), and gene expressions of the mutants, at 0.1 and 40 MPa. Additionally, we enhanced H2 tolerance in our model by adaptive laboratory evolution. “Evol”, the ensuing strain acclimatized to H2-saturating conditions for 76 generations, grew in 10% H2, contrarily to the parent strain. To understand such adaptation, we compared both strains’ end-products (H2, H2S, acetate), transcriptomes, and genomes.119 mutations were detected and the H2 metabolism was changed in the new variant. This work underlines the interest of Thermococcales’ piezophily for H2 bio-production and permits to propose optimization strategies
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Wheeler, Michael James. "Heterogeneous ice nucleation : laboratory freezing results and testing different schemes to describe ice nucleation in atmospheric models." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54274.
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Ice nucleation occurs throughout the atmosphere. Some atmospheric ice particles are formed through nucleation on insoluble atmospheric aerosols known as ice nuclei (IN). The abundance and chemical composition of these IN affect the properties of clouds and in turn the radiative balance of the Earth through the indirect effect of IN on climate. The indirect effect of IN on climate is one of the least understood topics in climate change. A better understanding of ice nucleation and better capabilities to parameterize ice nucleation are needed to improve the predictions of the effect of IN on climate. Using a temperature and humidity controlled flow cell coupled to an optical microscope, the ice nucleation properties of three different mineral dust particles are examined in two different freezing modes. Results showed that the freezing ability of supermicron dust particles is lower than that of submicron dust particles of the same type. These freezing results along with literature freezing results of nine biological aerosol particles are used to evaluate different schemes used to parameterize ice nucleation in atmospheric models. These schemes are evaluated based on the ability to reproduce the laboratory freezing results. It was found that a single parameter scheme based on classical nucleation theory was unable to reproduce the freezing results of all particles studied. However, more complex schemes were able to reproduce the freezing results.
The results in this thesis can be used by atmospheric modellers to improve predictions of mixed-phase and ice clouds and climate change.Science, Faculty of
Chemistry, Department of
Graduate
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El-Beyrouthi, Nayla. "RNA interference and somatic cell nuclear transfer to generate an apolipoprotein E deficient pig : a new model of atherosclerosis." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116103.
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Atherosclerosis is a complex disease which develops silently over decades and can lead to acute myocardial infarction or stroke, the main cause of death worldwide. Apoliporotein E (apo E) is a glycoprotein known for its major role in lipid metabolism and its pro-atherogenic effects. Swine make a unique and viable research model as it shares most of the anatomic and physiologic characteristics with humans, notably for the the cardiovascular system. In addition, it is the only animal species, other than nonhuman primates, that develops atherosclerosis spontaneously. In this study we examined the feasibility for creating an apo E-deficient pig model of atherosclerosis using RNA interference (RNAi) and somatic cell nuclear transfer (SCNT). The knockdown efficiency was tested in porcine granulosa cells. It varied from 45% to 82% compared to control cells, as revealed by real-time PCR analysis. Accordingly, short hairpin RNA-expressing vectors were constructed and used to transfect porcine fetal fibroblast cells. Cell lines with stable chromosomal integration were established and used to produce embryos by SCNT. Development of SCNT embryos to the blastocyst stage (33%) was comparable to non-transgenic embryos. The integration of the shRNA into the genome of GFP-expressing embryos was revealed by PCR and gel electrophoresis. These findings indicate that porcine embryos harboring shRNA-specific to apo E created by SCNT may lead to the production of apo E-deficient pigs. These pigs would be a promising new animal model for advancing atherosclerosis research.
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Xiang, Li. "Metabolomics study of regulatory effects of exercise training on db/db type 2 diabetic mice." HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/489.
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Type 2 diabetes mellitus (T2DM) is mainly caused by genetic modifications and inappropriate life styles. The complexity of T2DM has brought us challenges for a comprehensive understanding of altered metabolic pathways that contributing to the development of T2DM. Therefore, a comprehensive metabolic analysis is needed. To date, taking regular exercise is a common and effective therapeutic way known to antagonize the metabolic disorders of T2DM. However, the regulatory effects of exercise on T2DM or T2DM induced complications have not been clearly characterized. Here, we present the effect of physical activity on biochemical changes in diabetic db/db mice in plasma, urine, skeletal muscle and kidney samples. Based on liquid chromatography coupled with high resolution Orbitrap mass spectrometry (LC-MS) and gas chromatography coupled with mass spectrometry (GC-MS), two major approaches, untargeted and targeted metabolomics studies, have been developed to delineate metabolic signatures in various kinds of biofluid and tissue samples. Targeted quantification methods on acylcarnitines and acyl-CoA have been developed. Untargeted metabolomics analysis by GC-MS and LC-MS have also been developed to draw a more comprehensive view of the metabolic changes in response to T2DM and exercise on db/db diabetic mice. The transcript expressions of mRNA in pathways of interest have also been measured to confirm the hypothesis. Firstly, a targeted quantification method of acylcarnitines by using high resolution parallel reaction monitoring (PRM) on LC-MS platform has been developed. A total of 117 acylcarnitines were detected from plasma and urine samples. The application of targeted profiling of acylcarnitines in db/m+ control and db/db diabetic mice indicated incomplete amino acid and fatty acid oxidation in diabetic mice. Interestingly, the reduction of medium odd-numbered chain acylcarnitines in urine samples was firstly observed between db/m+ and db/db mice. The high resolution PRM method makes it possible to monitor the widespread metabolic changes of the acylcarnitines in response to stimuli. Besides, the accurate MS and MS/MS spectra data of the 117 acylcarnitines could be used as mass spectrometric resources for the identification of acylcarnitines. In addition to targeted metabolomics analysis, untargeted metabolomics profiling analysis in plasma samples indicated that db/db diabetic mice may be more susceptible to exercise for energy expenditure. Interestingly, all the results from plasma, skeletal muscle and kidney samples may demonstrate that physical activity could mitigate insulin resistance in T2DM mice through improving fatty acid β-oxidation (FAO) and eliminating overloaded intermediate which contribute to insulin resistance. Specifically, the results from kidney samples demonstrated that exercise exhibit beneficial effect in reducing hyperlipidemia, expression levels of inflammatory markers (TNFα, IL-6 and COX2) and fibrosis markers (Collagen 1), and alleviating diabetic nephropathy (DN) induced mesangial expansion in kidneys of diabetic mice. The results of metabolic changes in kidney of db/db mice revealed that the accumulation of acyl-CoA, phospholipids and hydroxylated acylcarnitines were substantially ameliorated by exercise, and the reduction of important enzymes CTP1α and Acadl in FAO were partially reversed. In addition, branched-chain amino acids (BCAA) metabolism which positively related to inflammation (TNFα) was down-regulated in DN mice by exercise. What’s more, the accumulation of uric acid, which contributes to inflammation and tubulointestitial fibrosis in kidney disease, together with its six precursors have also been substantially reduced. The results in kidney samples demonstrated that in addition to beneficial effect in alleviating lipotoxicity through improving FAO efficiency, exercise also ameliorated diabetic induced inflammation and fibrosis via promoting BCAA catabolism and accelerating the elimination of uric acid. Together, the mass spectrometry-based metabolomics study is a powerful tool to investigate the regulatory effect of exercise on complex metabolic diseases. The results may provide informative insights into the underlying the mechanism of exercise on T2DM and T2DM induced complications.
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McDonald, Jamin. "Comparison of data from an laboratory exercise for Geological sciences 245 : Computational geology, to resurfacing models for Venus /." Columbus, Ohio : Ohio State University, 2000. http://hdl.handle.net/1811/24124.
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Li, Zhuoming, and 李卓明. "Heme oxygenase-1 and endothelial dysfunction in the spontaneously hypertensive rat." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48521735.
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The endothelium is important for the regulation of vascular tone. In diseases like hypertension, the endothelial cells become dysfunctional. This dysfunction is characterized by nitric oxide (NO) deficiency, impairment of endothelium-dependent hyperpolarization (EDH) and the overwhelming production of endothelium-derived contracting factor (EDCF). Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme, producing carbon monoxide(CO), bilirubin and free iron. Up-regulation of the inducible isoform (HO-1) of the enzyme lowers blood pressure in animals. The purpose of the present study was to investigate whether or not up-regulation of HO-1by the pharmacological agent hemin improves endothelial function in arteries of spontaneously hypertensive rats(SHR).
Twenty four hours after intraperitoneal injection of hemin (50mg/kg) in 36 weeks old SHR, the expression and activity of HO-1 were augmented, in both the endothelium and vascular smooth muscle. Hemin-treatment potentiated endothelium-dependent relaxations to the muscarinic agonist acetylcholine in both the aorta and the mesenteric artery, whereas the HO inhibitor protoporphyrin IX zinc (II) (ZnPP; 30 mg/kg) prevented the beneficial effect of hemin, suggesting that HO-1 induction improves endothelial function.
Hemin-treatment did not augment acetylcholine-induced NO-mediated relaxations, and did not alter the expression level of either phosphorylated eNOS (Ser1177) or total eNOS, suggesting that the improvement of endothelial function by HO-1 induction cannot be attributed to an increased bioavailability of NO.
In the mesenteric arteries, hemin treatment potentiated acetylcholine-evoked EDH-mediated relaxations in the presence of L-NAME and indomethacin. The IKCa channel blocker TRAM-34andthe Na+-K+-ATPase blocker ouabain significantly impaired these hemin-potentiated relaxations. NS309-induced TRAM-34-and ouabain-sensitive relaxations were enhanced by hemin-treatment. K+-induced ouabain-sensitive relaxations and the expression of Na+-K+-ATPase were increased by hemin-treatment. Taken in conjunction, these observations imply that the improved EDH-mediated relaxations by HO-1 induction is due to an improvement of IKCa-Na+-K+-ATPase pathway. Treatment with an antioxidant apocynin (50mg/kg) showed a similar effect as hemin, and the combined treatment with hemin and apocynin did not cause a greater improvement. In vitro treatment with bilirubin, enhanced EDH responses and K+-induced ouabain-sensitive relaxations. These observations suggest that the effect of HO-1 induction on EDH-mediated relaxations is possibly due to its antioxidant properties and the production of bilirubin.
In the aortae, hemin-treatment reduced endothelium-dependent contractions in response to acetylcholineor to a calcium ionophoreA23187. Production of reactive oxygen species (ROS) was suppressed by hemin-treatment, judging from the results of 2’,7’-dichlorodihydrofluoresein diacetate staining, dihydroethidium staining and lucigenin chemiluminescence, which was attributed to the decreased expressions of NADPH oxidase-2 (Nox2) and cyclooxygenase-1(COX-1). The production of prostacyclin was decreased, which was explained by a lower expression of COX-1. Contractions to vasoconstrictor concentrations of prostacyclin and its mimetic iloprost were attenuated, suggesting that the responsiveness of thromboxane-prostanoid receptors (TP receptors) to prostacyclin was decreased by hemin-treatment. The effects of HO-1 on the suppressed production of ROS and prostacyclin, and the decreased responsiveness of TP receptors, contribute to its inhibitory role on EDCF-mediated response.
Thus, up-regulation of HO-1 improves endothelial function in the SHR by potentiating EDH response and impairing EDCF.published_or_final_version
Pharmacology and Pharmacy
Doctoral
Doctor of Philosophy
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Carney, Katharine W. "Expression patterns and functional roles of amphiregulin in murine CD4+ T cells." Thesis, Royal Veterinary College (University of London), 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669191.
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Fischer, Manfred M., Rico Maggi, and Christian Rammer. "Scholarly Communication in Europe. Stated Communication Media Choice and Contact Decision Models Based on Laboratory Choice Experiments In Universities." WU Vienna University of Economics and Business, 1992. http://epub.wu.ac.at/4215/1/WSG_DP_1892.pdf.
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Cross, James A. "A comparison of sound exposure profiling with the basic sound survey as applied in an academic laboratory environment." Oklahoma City : [s.n.], 2003. http://library.ouhsc.edu/epub/theses/Cross-James-Allyn.pdf.
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Hilbelink, Amy JoAnne. "The effectiveness and user perception of 3-dimensional digital human anatomy in an online undergraduate anatomy laboratory." [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0001876.
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Kam, Siu-kei Christy. "Detection of anti-nuclear antibody responses induced by dendritic cells that have captured dying cells in mouse models." Click to view the E-thesis via HKUTO, 2003. http://sunzi.lib.hku.hk/hkuto/record/B31971842.
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Woodcock, J. S. "Field and laboratory studies into the human response to groundborne vibration : exposure-response relationships, perceptual dimensions, and models of annoyance." Thesis, University of Salford, 2013. http://usir.salford.ac.uk/29280/.
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With proposed increases in both freight and passenger railway in the United Kingdom and the European Union and the building of new high speed lines, there has been an increase in interest in recent years in the human response to vibration in residential environments. As with exposure to environmental noise, exposure to environmental vibration can result in adverse effects such as annoyance and sleep disturbance. However, unlike exposure to environmental noise, well established relationships to evaluate annoyance caused by vibration in residential environments do not exist. In order to predict and control annoyance caused by vibration from environmental sources, a better understanding is needed of how humans perceive vibration and how their perception relates to measureable, quantifiable features of the vibration exposure. In the work presented in this thesis, the human response to vibration is considered on both a community and individual level. The first major aim of this work is to develop statistically robust exposure-response relationships for the human response to railway and construction induced vibration in residential environments. This is achieved via a large scale field survey in which 1431 questionnaires were conducted with residents in their own homes along with extensive vibration measurements at internal and external positions. Analysis of the data collected through this field survey shows that all of the vibration exposure descriptors advocated in national and international standards are equally well correlated with annoyance due to railway induced vibration. Using a grouped regression model, exposure-response relationships describing the proportion of respondents expected to express annoyance above a given threshold are derived for railway and construction induced vibration in terms of a variety of vibration exposure descriptors. The second major aim of this work is to investigate the perception of railway induced vibration on an individual level by investigating the salient dimensions of the perception of whole body vibration. This is achieved via a subjective laboratory test in which paired comparisons of similarity and annoyance are conducted using fourteen measured railway vibration stimuli. Through multidimensional scaling analysis, it is shown that the perception of railway induced vibration is dependent on up to four perceptual dimensions. These dimensions relate to energy in the 16 Hz 1/3 octave band, energy in the 32 Hz 1/3 octave band, the duration of the train passage, and the modulation frequency of the envelope of the signal. These perceptual dimensions are related to single figure Perceived Annoyance Ratings (A) by the following relationship: $A=-0.40+4.57{{\ddot{X}}_{RMS,16Hz}}+3.18{{\ddot{X}}_{RMS,32Hz}}+0.02{{T}_{10dB}}+0.02f{}_{\bmod }$. Finally, the single figure Perceived Annoyance Ratings are related to categorical ratings of annoyance via a logistic regression model.
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Daggett, Jenny. "Evaluation and characterisation of two zebrafish models of schizophrenia." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/9603.
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Cognitive deficits are the single strongest predictor of the functional outcome in patients with schizophrenia. Current treatments are largely ineffective in improving cognitive impairments and promising pre-clinical research has mostly failed to translate clinically. Despite the advances provided by rodent models, the neurobiological basis of cognitive deficits in schizophrenia is poorly understood. Therefore, this thesis proposes a zebrafish model for studying cognitive impairments of schizophrenia. Although more evolutionarily distant to humans compared to the rat, the zebrafish has emerged as a popular vertebrate model of human disorders due to its genetic tractability, complex nervous system and elaborate behavioural repertoire. We investigated the effects of genetic alterations and neurodevelopmental disruption on behaviour and learning in zebrafish. Using both disc1 mutant lines and sub-chronic phencyclidine (PCP) on larvae from 6-10 dpf, we were able to assess behavioural changes as a function of developmental age. In particular, this thesis aimed to develop appropriate behavioural assays to assess zebrafish learning and executive function relevant to disorders seen in human patients with schizophrenia. It was possible to demonstrate robust learning across several domains, namely, reversal, classical avoidance and non-associative learning, alongside locomotor and anxiety-related behaviours. There were varied deficits associated with each of the two – genetic (disc1 gene mutation) and environmental (sub-chronic PCP) – manipulations, consistent with observations in rat research. Together, the research in this thesis demonstrates that a zebrafish model exhibits behaviour resembling that of mammalian models of schizophrenia and provides a foundation for the utility of zebrafish in examining cognitive impairments associated with schizophrenia.
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Onyango, Mbakisya A. "Verification of mechanistic prediction models for permanent deformation in asphalt mixes using accelerated pavement testing." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1362.
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Benevides, Aline de Lima. "O acento primário em pseudopalavras: uma abordagem experimental." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/8/8139/tde-03052017-090648/.
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Esta dissertação tem por objetivo investigar o papel que a frequência dos tipos silábicos desempenha na atribuição acentual em pseudopalavras produzidas por falantes nativos do Português Brasileiro através de metodologias experimentais. Contrapuseram-se, para isso, dados empíricos, provenientes de um experimento, a hipóteses fonológicas para o acento primário em PB. As propostas analisadas consistiram em: Hipótese Lexical (CÂMARA JR., 1970 [2001]), Hipótese Métrica (BISOL, 1994), Hipótese Morfológica (LEE, 1995) e Hipótese Multirrepresentacional (CANTONI, 2013). Esta pesquisa está norteada nos pressupostos dos Modelos Multirrepresentacionais. Fez-se necessária a compilação de um corpus linguístico que permitisse a extração da frequência dos padrões fonológicos requeridos na presente investigação, o qual é denominado de Corpus ABG. O experimento, que se subdividiu em dois grupos experimentais, inquiriu a relevância dos tipos silábicos [niw], [Voral.tʃiw], [Vnasal.tʃiw], [-oɾ] e [-aɾ] nos estudos acentuais. O grupo de análise 1, composto pelos tipos silábicos [niw], [Voral.tʃiw], [Vnasal.tʃiw], investigou, por meio do conceito de lacuna fonológica, se a frequência dos tipos silábicos impacta na determinação da localização acentual. O grupo de análise 2, composto pelos tipos silábicos [-oɾ] e [-aɾ], verificou em que medida a frequência dos tipos silábicos interage com processos analógicos, tendo como motivação a frequência de vocábulos fonológicos similares. Os resultados do experimento sugerem que, ao contrário do que preveem as propostas algorítmicas, todos os padrões acentuais (proparoxítono, paroxítono e oxítono) podem emergir - e emergiram. As produções acentuais encontradas no experimento trazem indícios de que a frequência dos tipos silábicos impacta na forma como o acento é atribuído no PB, bem como trazem evidências de que processos analógicos podem interagir com a produtividade na atribuição acentual. Os resultados, portanto, indicam que diferentes fatores, em diferentes níveis de abstração, são responsáveis pela atribuição acentual no PB.This dissertation aims to investigate the role that the frequency of the syllabic types plays in the stress assignment in pseudowords produced by native speakers of Brazilian Portuguese through experimental methodologies. For this, empirical data, originating from an experiment, were contrasted to phonological hypotheses for the primary stress in BP. The proposals analyzed consisted of: Lexical Hypothesis (CÂMARA JR., 1970 [2001]), Metrical Hypothesis (BISOL, 1994), Morphological Hypothesis (LEE, 1995) and Multirepresentational Hypothesis (CANTONI, 2013). This research is guided on the assumptions of the Multirepresentational Models. A compilation of a linguistic corpus was necessary to allow the extraction of the frequency of the phonological patterns required in the present investigation, which is named Corpus ABG. The experiment, which was subdivided into two experimental groups, inquired about the relevance of the syllabic types [niw], [Voral.tʃiw], [Vnasal.tʃiw], [-oɾ] and [-aɾ] in the stress studies. Analysis group 1, composed of the syllabic types [niw], [Voral.tʃiw] and [Vnasal.tʃiw], investigated, through the concept of phonological gap, whether the frequency of the syllabic types has an impact on the determination of the stress location. Analysis group 2, composed of the syllabic types [-oɾ] and [-aɾ], verified to what extent the frequency of the syllabic types interacts with analogical processes, motivated by the frequency of similar phonological vocables. The results of the experiment demonstrated that, contrary to what the algorithmic proposals foresee, all the stress patterns (proparoxitone, paroxitone and oxytone) can emerge - and emerged. The stress productions found in the experiment indicate that the frequency of the syllabic types impacts on how the stress is assigned in BP, as well as provides evidences that analogical processes can interact with productivity in stress assignment. The results, therefore, demonstrate that different factors, at different levels of abstraction, are responsible for the stress assignment in BP.