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Dissertationen zum Thema „Transport imaging“

Autor: Grafiati

Veröffentlicht am 4. Juni 2021

Zuletzt aktualisiert am 1. Februar 2022

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1

Norris, David G. „Diffusion imaging of the brain“. Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196833.

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This chapter presents a brief introduction to the application of diffusion-weighted magnetic resonance imaging (MRI) to in vivo studies. Diffusion-weighted MRI has found application both in the clinic, and in basic neuroscience. In the former situation it is primarily used for the detection of brain lesions, in particular infarcted regions. The ability to follow fibre tracts in white matter via diffusion tensor imaging has also made this methodology of interest to the neurosurgeon wishing to avoid severance of essential fibre tracts, but also of interest to the cognitive neuroscientist exploring anatomical connectivity in the brain. The chapter starts with a brief recap of the theory of diffusionweighted MRI and moves on to examine the two major experimental confounds, eddy currents and bulk motion. Current correction schemes for these problems are touched upon. Diffusion anisotropy is introduced as a potential source of artefacts for lesion detection in white matter, and the diffusion tensor model presented. The chapter concludes with a short introduction to fibre tracking.

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2

Böhm, Andreas. „Imaging of light induced carrier transport“. [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9820898.

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3

Winchell, Stephen D. „Transport imaging in the one dimensional limit“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FWinchell.pdf.

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4

Lock, John George. „Dynamic imaging of post-Golgi protein transport /“. [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19397.pdf.

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5

Waller, Laura A. (Laura Ann). „Computational phase imaging based on intensity transport“. Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60821.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 133-150).
Light is a wave, having both an amplitude and a phase. However, optical frequencies are too high to allow direct detection of phase; thus, our eyes and cameras see only real values - intensity. Phase carries important information about a wavefront and is often used for visualization of biological samples, density distributions and surface profiles. This thesis develops new methods for imaging phase and amplitude from multi-dimensional intensity measurements. Tomographic phase imaging of diffusion distributions is described for the application of water content measurement in an operating fuel cell. Only two projection angles are used to detect and localize large changes in membrane humidity. Next, several extensions of the Transport of Intensity technique are presented. Higher order axial derivatives are suggested as a method for correcting nonlinearity, thus improving range and accuracy. To deal with noisy images, complex Kalman filtering theory is proposed as a versatile tool for complex-field estimation. These two methods use many defocused images to recover phase and amplitude. The next technique presented is a single-shot quantitative phase imaging method which uses chromatic aberration as the contrast mechanism. Finally, a novel single-shot complex-field technique is presented in the context of a Volume Holographic Microscopy (VHM). All of these techniques are in the realm of computational imaging, whereby the imaging system and post-processing are designed in parallel.
by Laura A. Waller.
Ph.D.

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6

Bos, Kevin J., K. Gordon Wilson und Benedict Newling. „Velocity-sensitised Magnetic Resonance Imaging of foams“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184242.

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Although flowing foams are used in a variety of technologies, foam rheology is still incompletely understood. In this paper we demonstrate the use of a velocity-sensitised magnetic resonance imaging (MRI) sequence for the study of flowing foam. We employ a constant-time (pure phase encode) imaging technique, SPRITE, which is immune to geometrical distortions caused by the foam-induced magnetic field inhomogeneity. The sample magnetisation is prepared before the SPRITE imaging with the Cotts 13-interval motion-sensitisation sequence, which is also insensitive to the effects of the foam heterogeneity. We measure the development of a power-law velocity profile in the foam downstream of a Venturi constriction (in which the cross-section of the tube decreases by 89% in area) in a vertical, cylindrical pipe.

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7

Maximov, Ivan I., Farida Grinberg und Nadim Jon Shah. „Robust estimator framework in diffusion tensor imaging“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184368.

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Diffusion of water molecules in the human brain tissue has strong similarities with diffusion in porous media. It is affected by different factors such as restrictions and compartmentalization, interaction with membrane walls, strong anisotropy imposed by cellular microstructure, etc. However, multiple artefacts abound in in vivo measurements either from subject motions, such as cardiac pulsation, bulk head motion, respiratory motion, and involuntary tics and tremor, or hardware related problems, such as table vibrations, etc. All these artefacts can substantially degrade the resulting images and render postprocessing diffusion analysis difficult or even impossible. In order to overcome these problems, we have developed a robust and efficient approach based on the least trimmed squares algorithm that works well with severely degraded datasets with low signal-to-noise ratio. This approach has been compared with other diffusion imaging post-processing algorithms using simulations and in vivo experiments. We demonstrate that the least trimmed squares algorithm can be easily adopted for multiple non-Gaussian diffusion models such as the biexponential model. The developed approach is shown to exhibit a high efficiency and accuracy and can, in principle, be exploited in other diffusion studies where artefact/outlier suppression is demanded.

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8

Salameh, Wassim, Sébastien Leclerc, Didier Stemmelen und Jean-Marie Escanyé. „NMR imaging of water flow in packed beds“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186395.

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Measurements by magnetic resonance imaging (MRI) of water flow within granular porous media are presented in this study. Our goal was not only to obtain visualizations of velocity field in porous media but rather to make accurate measurements of interstitial and averaged velocities in bead packs. Two situations were examined: the first for a packed bed with a large beads diameter where it was possible to visualize the interstitial velocities and the second with a packed bed with a small beads diameter where only averaged interstitial velocities were measured.

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9

Steele, Gary Alexander. „Imaging transport resonances in the quantum Hall effect“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34401.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
MIT Institute Archives copy: p. 201-231 bound in reverse order.
Includes bibliographical references (p. 213-231).
We image charge transport in the quantum Hall effect using a scanning charge accumulation microscope. Applying a DC bias voltage to the tip induces a highly resistive ring-shaped incompressible strip (IS) in a very high mobility 2D electron system (2DES). The IS moves with the tip as it is scanned, and acts as a barrier that prevents charging of the region under the tip. At certain tip positions, short-range disorder in the 2DES creates a quantum dot island inside the IS that enables breaching of the IS barrier by means of resonant tunneling through the island. Striking ring shapes appear in the images that directly reflect the shape of the IS created in the 2DES by the tip. Through the measurements of leakage across the IS, we extract information about energy gaps in the quantum Hall system. Varying the magnetic field, the tunneling resistance of the IS varies significantly, and takes on drastically different values at different filling factors. Measuring this tunneling resistance provides a unique microscopic probe of energy gaps in the quantum Hall system. Simulations of the interaction of the tip with the quantum Hall liquid show that native disorder from remote ionized donors can create the islands. The simulations predict the shape of the IS created in the 2DES in the presence of disorder, and comparison of the images with simulation results provides a direct and quantitative view of the disorder potential of a very high mobility 2DES. We also draw a connection to bulk transport. At quantum Hall plateaus, electrons in the bulk are localized by a network of ISs.
We have observed that the conductance across one IS is drastically enhanced by resonant tunneling through quantum dot islands. Similarly, this resonant tunneling process will dramatically enhance the conductance of certain hopping paths in the localized bulk and could play an important role in dissipative transport at quantum Hall plateaus.
by Gary Alexander Steele.
Ph.D.

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10

Dean, Ryan J., Timothy Stait-Gardner, Simon J. Clarke, Suzy Y. Rogiers und William S. Pricea. „Diffusion Tensor Imaging (DTI) studies of the grape berry“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184852.

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11

Granick, Steve. „Surprises from single-particle imaging of passive and active diffusion“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179310.

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12

Bos, Kevin J., K. Gordon Wilson und Benedict Newling. „Velocity-sensitised Magnetic Resonance Imaging of foams“. Diffusion fundamentals 18 (2013) 5, S. 1-4, 2013. https://ul.qucosa.de/id/qucosa%3A13711.

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Although flowing foams are used in a variety of technologies, foam rheology is still incompletely understood. In this paper we demonstrate the use of a velocity-sensitised magnetic resonance imaging (MRI) sequence for the study of flowing foam. We employ a constant-time (pure phase encode) imaging technique, SPRITE, which is immune to geometrical distortions caused by the foam-induced magnetic field inhomogeneity. The sample magnetisation is prepared before the SPRITE imaging with the Cotts 13-interval motion-sensitisation sequence, which is also insensitive to the effects of the foam heterogeneity. We measure the development of a power-law velocity profile in the foam downstream of a Venturi constriction (in which the cross-section of the tube decreases by 89% in area) in a vertical, cylindrical pipe.

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13

Maximov, Ivan I., Farida Grinberg und Nadim Jon Shah. „Robust estimator framework in diffusion tensor imaging“. Diffusion fundamentals 18 (2013) 10, S. 1-6, 2013. https://ul.qucosa.de/id/qucosa%3A13717.

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Diffusion of water molecules in the human brain tissue has strong similarities with diffusion in porous media. It is affected by different factors such as restrictions and compartmentalization, interaction with membrane walls, strong anisotropy imposed by cellular microstructure, etc. However, multiple artefacts abound in in vivo measurements either from subject motions, such as cardiac pulsation, bulk head motion, respiratory motion, and involuntary tics and tremor, or hardware related problems, such as table vibrations, etc. All these artefacts can substantially degrade the resulting images and render postprocessing diffusion analysis difficult or even impossible. In order to overcome these problems, we have developed a robust and efficient approach based on the least trimmed squares algorithm that works well with severely degraded datasets with low signal-to-noise ratio. This approach has been compared with other diffusion imaging post-processing algorithms using simulations and in vivo experiments. We demonstrate that the least trimmed squares algorithm can be easily adopted for multiple non-Gaussian diffusion models such as the biexponential model. The developed approach is shown to exhibit a high efficiency and accuracy and can, in principle, be exploited in other diffusion studies where artefact/outlier suppression is demanded.

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14

Titze, Tobias, Christian Chmelik, Dirk Enke, Roger Gläser, Jens Kullmann, Jörg Kärger, Lutz Prager und Jens Weitkamp. „Exploring diffusion and reaction in nanoporous catalysts by IR micro-imaging“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183231.

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15

Heidernätsch, Mario, Michael Bauer, Daniela Täuber, Günter Radons und Christian von Borcyskowski. „An advanced method of tracking temporarily invisible particles in video imaging“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191774.

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16

Parasoglou, Prodromos, Andrew J. Sederman, John Rasburn, Hugh Powell und Michael L. Johns. „Optimal k-space sampling for single point imaging of transient systems“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192138.

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A modification of the Single Point Imaging (SPI) is presented. The novel approach aims at increasing the sensitivity of the method and hence the resulting Signal-to-Noise ratio (SNR) for a given total time interval. With prior knowledge of the shape of the object under study, a selective sparse k-space sampling can then be used to follow dynamic phenomena of transient systems, in this case the absorption of moisture by a cereal-based wafer material. Further improvement in the image quality is achieved when the un-sampled k-space points are replaced by those of the initial dry or the final wet sample acquired at the beginning and the end of the acquisition respectively when there are no acquisition time limitations.

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17

Bhallamudi, Vidya Praveen. „Spins in heterogeneous landscapes: Consequences for transport and imaging“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306871981.

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18

Dorcéna, Cassandre Jenny. „Nanoparticles for Biomedical Imaging and Biomolecular Transport and Manipulation“. The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408915572.

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19

Salameh, Wassim, Sébastien Leclerc, Didier Stemmelen und Jean-Marie Escanyé. „NMR imaging of water flow in packed beds“. Diffusion fundamentals 14 (2010) 5, S. 1-5, 2010. https://ul.qucosa.de/id/qucosa%3A13854.

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Measurements by magnetic resonance imaging (MRI) of water flow within granular porous media are presented in this study. Our goal was not only to obtain visualizations of velocity field in porous media but rather to make accurate measurements of interstitial and averaged velocities in bead packs. Two situations were examined: the first for a packed bed with a large beads diameter where it was possible to visualize the interstitial velocities and the second with a packed bed with a small beads diameter where only averaged interstitial velocities were measured.

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20

Tao, Lian, Anna Tao, Robert G. Thorne und Charles Nicholson. „Integrative optical imaging of molecular diffusion in strong light scattering brain tissue“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183663.

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21

Nakagawa, Satoshi, Kazuyuki Chihara und Kuniyasu Ogawa. „2D Projective imaging of water concentration profiles in adsorption columns by MRI“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185019.

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22

Vogel, Patrick, Martin Andreas Rückert, Peter Klauer, Walter H. Kullmann, Peter Michael Jakob und Volker Christian Behr. „Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179243.

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Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging (MRI) or computer tomography (CT) offer anon-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and non-magnetic behaviour. In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner.

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23

Dean, Ryan J., Timothy Stait-Gardner, Simon J. Clarke, Suzy Y. Rogiers und William S. Pricea. „Diffusion Tensor Imaging (DTI) studies of the grape berry“. Diffusion fundamentals 16 (2011) 29, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13762.

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24

Kossel, Elke, Christian Deusner, Nikolaus Bigalke und Matthias Haeckel. „Magnetic Resonance Imaging of gas hydrate formation and conversion at sub-seafloor conditions“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184430.

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The production of natural gas from sub-seafloor gas hydrates is one possible strategy to meet the world’s growing demand for energy. On the other hand, climate warming scenarios call for the substitution of fossil energy resources by sustainable energy concepts. Burning natural gas from gas hydrates could be emission neutral if it was combined with a safe storage of the emitted CO2. Laboratory experiments, that address corresponding strategies, need to be performed under high pressures and low temperatures to meet the thermodynamic conditions of the sub-seafloor environment. In this paper, we present a high-pressure flow-through sample cell that is suitable for nuclear magnetic resonance (NMR) experiments at realistic marine environmental conditions, i.e. pressures up to 15 MPa and temperatures from 5 to 20°C, and we demonstrate its suitability in applied gas hydrate research.

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25

Luber, David R. „Direct imaging of minority charge carrier transport in luminescent semiconductors“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FLuber.pdf.

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Thesis (M.S. in Space Systems Operations and M.S. in Applied Physics)--Naval Postgraduate School, September 2005.
Thesis Advisor(s): Nancy M. Haegel, Sherif Michael. Includes bibliographical references (p.55-56). Also available online.

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26

Ang, Goon Hwee. „Transport imaging for the study of nanowires and related nanostructures“. Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FAng.pdf.

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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2007.
Thesis Advisor(s): Haegel, Nancy M. ; Luscombe, James. "December 2007." Description based on title screen as viewed on January 17, 2008. Includes bibliographical references (p. 83-85). Also available in print.

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27

Ong, Zi Xuan. „Transport imaging of multi-junction and CIGS solar cell materials“. Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10665.

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Multi-junction solar cells are an emerging technology that improves the conversion rate of solar energy. Indium Gallium Phosphide (InGaP) is commonly used as the top cell in multi-junction cells grown on Germanium (Ge) or Gallium Arsenide (GaAs) substrates. To design more efficient solar cells using InGaP, it is important to characterize its transport parameters, particularly the minority charge carrier mobility, diffusion length and lifetime as a function of doping and material growth conditions. In this work, transport imaging was performed on a set of InGaP heterostructures (with differing thicknesses, doping levels and minority carrier types) to determine their minority carrier diffusion length. These measurements, together with an independent set of time-resolved photoluminescence (TRPL) lifetime data, were used to calculate the minority carrier mobility values. For the shortest diffusion lengths, experimental limitations were encountered involving the finite carrier generation volume. Simulations were performed to explore the potential of modeling the convolution of diffusion behavior with a finite generation region to address these limitations. Transport imaging was also performed on a set of Copper Indium Gallium Selenide (CIGS) materials. Polycrystalline CIGS represents an alternative to the expensive single-crystal InGaP. These initial experiments identified the challenges of applying transport imaging to polycrystalline materials.

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28

Naik, Nikhil (Nikhil Deepak). „Multibounce light transport analysis using ultrafast imaging for material acquisition“. Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76529.

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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 92-96).
This thesis introduces a novel framework for analysis of multibounce light transport using time-of-flight imaging for the applications of ultrafast reflectance acquisition and imaging through scattering media. Using ultrafast imaging and ultrafast illumination, we analyze light indirectly scattered off materials to provide new insights into the important problem of material acquisition. We use an elegant matrix based representation of light transport, which enables scene reconstruction using standard optimization techniques. We demonstrate the accuracy and efficiency of our methods using various simulations as well as an experimental setup. In particular, we develop the concept of 'in the wild' reflectance estimation using ultrafast imaging. We demonstrate a new technique that allows a camera to rapidly acquire reflectance properties of objects from a single viewpoint, over relatively long distances and without encircling equipment. We measure material properties by indirectly illuminating an object by a laser source, and observing its reflected light indirectly using a time-of-fight camera. As compared to lengthy or highly calibrated reflectance acquisition techniques, we demonstrate a device that can rapidly and simultaneously capture meaningful reflectance information of multiple materials. Furthermore, we use this framework to develop a method for imaging through scattering media using ultrafast imaging. We capture the diffuse scattering in the scene with a time-of- flight camera and analyze the multibounce light transport to recover albedo and depth information of planar objects hidden behind a diffuser. The methods developed in this thesis using ultrafast imaging can spur research with novel real-time applications in computer graphics, medical imaging and industrial photography.
by Nikhil Naik.
S.M.

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29

Grange, Michael. „Integrative imaging and electron cryo-tomography of viral transport mechanisms“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:704e3459-053a-4a1c-b95a-9aaeca809cb2.

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To comprehensively understand a biological process or mechanism from molecule to cell it requires the combination of multiple techniques across a range of resolutions and scales. We currently rely on a variety of different approaches to highlight given aspects of biology that are then interlinked through interpretation. Intracellular transport is a process whereby vesicles and organelles are transported to different parts of cells with a precise spatial and temporal accuracy. This process is often hijacked by viruses, which utilize cellular machineries for active transport to and from the nucleus during their entry and egress. In this thesis I focus on the intracellular transport of adenoviruses, which are able to recruit and bind to the cytoskeletal motor, dynein, and use it to travel to the nucleus. I apply electron cryo-microscopy and fluorescence microscopy to elucidate the basis for this process, and link this to the behaviour of adenoviruses as they are recruited to microtubules. I then apply electron cryo-tomography to directly observe proteins in their native cellular environment. I discuss the ability of this technique to be utilized in the in situ determination of the structure of viruses as they infect a cell. I show that (i) in situ sub-volume averaging from single tomograms can guide and complement segmentation of biological features and (ii) that novel, transient processes can be imaged with high levels of detail. As a second example of transport in cells, I study the nuclear egress of herpesvirus capsids, utilizing a multi-modal approach in an attempt to characterize this process from cellular to molecular level, and ask how herpesviruses modulate the nuclear membrane during capsid egress into the cytosol. Finally, I discuss an emergent technique in the field of electron cryo-microscopy, the Volta phase plate, its potential application in molecular tomography, and how it may enhance our current ability to discern contextual molecular mechanism.

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30

Vogel, Patrick, Martin Andreas Rückert, Peter Klauer, Walter H. Kullmann, Peter Michael Jakob und Volker Christian Behr. „Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock: Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock“. Diffusion fundamentals 22 (2014) 12, S.1-5, 2014. https://ul.qucosa.de/id/qucosa%3A13518.

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Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging (MRI) or computer tomography (CT) offer anon-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and non-magnetic behaviour. In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner.

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31

Granick, Steve. „Surprises from single-particle imaging of passive and active diffusion“. Diffusion fundamentals 20 (2013) 1, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13521.

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32

Norris, David G. „Diffusion imaging of the brain: technical considerations and practical applications“. Diffusion fundamentals 2 (2005) 115, S. 1-12, 2005. https://ul.qucosa.de/id/qucosa%3A14454.

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This chapter presents a brief introduction to the application of diffusion-weighted magnetic resonance imaging (MRI) to in vivo studies. Diffusion-weighted MRI has found application both in the clinic, and in basic neuroscience. In the former situation it is primarily used for the detection of brain lesions, in particular infarcted regions. The ability to follow fibre tracts in white matter via diffusion tensor imaging has also made this methodology of interest to the neurosurgeon wishing to avoid severance of essential fibre tracts, but also of interest to the cognitive neuroscientist exploring anatomical connectivity in the brain. The chapter starts with a brief recap of the theory of diffusionweighted MRI and moves on to examine the two major experimental confounds, eddy currents and bulk motion. Current correction schemes for these problems are touched upon. Diffusion anisotropy is introduced as a potential source of artefacts for lesion detection in white matter, and the diffusion tensor model presented. The chapter concludes with a short introduction to fibre tracking.

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33

Nguyen, Thoa T. M., Andrew J. Sederman und Lynn F. Gladden. „Characterisation of pulsing flow in trickle-bed reactors using ultra-fast magnetic resonance imaging“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192286.

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We use ultra-fast Magnetic Resonance Imaging (MRI) to characterise hydrodynamics during pulsing flow in trickle-bed reactors. One-dimensional (1-D) liquid holdup profiles along the flow direction were acquired using Fast Low Angle SHot (FLASH) MRI at spatial and temporal resolutions of 352 μm pixel-1 and 3.3 ms, respectively. Liquid pulse properties such as pulse velocity, duration and frequency obtained with MRI are in good agreement with those measured using a well established technique called the conductance method. In addition, MRI gives local measurements and provides additional spatial information to track individual liquid pulses, which cannot be obtained with the conductance method approach.

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34

Titze, Tobias, Christian Chmelik, Dirk Enke, Roger Gläser, Jens Kullmann, Jörg Kärger, Lutz Prager und Jens Weitkamp. „Exploring diffusion and reaction in nanoporous catalysts by IR micro-imaging“. Diffusion fundamentals 20 (2013) 58, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13635.

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35

Heidernätsch, Mario, Michael Bauer, Daniela Täuber, Günter Radons und Christian von Borcyskowski. „An advanced method of tracking temporarily invisible particles in video imaging“. Diffusion fundamentals 11 (2009) 111, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A14085.

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36

Parasoglou, Prodromos, Andrew J. Sederman, John Rasburn, Hugh Powell und Michael L. Johns. „Optimal k-space sampling for single point imaging of transient systems“. Diffusion fundamentals 10 (2009) 13, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14104.

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A modification of the Single Point Imaging (SPI) is presented. The novel approach aims at increasing the sensitivity of the method and hence the resulting Signal-to-Noise ratio (SNR) for a given total time interval. With prior knowledge of the shape of the object under study, a selective sparse k-space sampling can then be used to follow dynamic phenomena of transient systems, in this case the absorption of moisture by a cereal-based wafer material. Further improvement in the image quality is achieved when the un-sampled k-space points are replaced by those of the initial dry or the final wet sample acquired at the beginning and the end of the acquisition respectively when there are no acquisition time limitations.

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37

Aaron, Douglas Scott. „Transport in fuel cells: electrochemical impedance spectroscopy and neutron imaging studies“. Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34699.

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Current environmental and energy sustainability trends have instigated considerable interest in alternative energy technologies that exhibit reduced dependence on fossil fuels. The advantages of such a direction are two-fold: reduced greenhouse gas emissions (notably CO2) and improved energy sustainability. Fuel cells are recognized as a potential technology that achieves both of these goals. However, improvements to fuel cell power density and stability must be realized to make them economically competitive with traditional, fossil-based technologies. The work in this dissertation is largely focused on the use of analytical tools for the study of transport processes in three fuel cell systems toward improvement of fuel cell performance. Polymer electrolyte membrane fuel cells (PEMFCs) are fueled by hydrogen and oxygen to generate electrical current. Microbial fuel cells (MFCs) use bacteria to degrade carbon compounds, such as those found in wastewaters, and simultaneously generate an electric current. Enzyme fuel cells (EFCs) operate similarly to PEMFCs but replace precious metal catalysts, such as platinum, with biologically-derived enzymes. The use of enzymes also allows EFCs to utilize simple carbon compounds as fuel. The operation of all three fuel cell systems involves different modes of ion and electron transport and can be affected negatively by transport limitations. Electrochemical impedance spectroscopy (EIS) was used in this work to study the distribution of transport resistances in all three fuel cell systems. The results of EIS were used to better understand the transport resistances that limited fuel cell power output. By using this technique, experimental conditions (including operating conditions, construction, and materials) were identified to develop fuel cells with greater power output and longevity. In addition to EIS, neutron imaging was employed to quantify the distribution of water in PEMFCs and EFCs. Water content is an integral aspect of providing optimal power output from both fuel cell systems. Neutron imaging contributed to developing an explanation for the loss of water observed in an operating EFC despite conditions designed to mitigate water loss. The findings of this dissertation contribute to the improvement of fuel cell technology in an effort to make these energy devices more economically viable.

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38

Rauscher, Brian Craig. „In-situ optical imaging of carrier transport in multilayer solar cells“. Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://handle.dtic.mil/100.2/ADA483453.

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Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2008.
Thesis Advisor(s): Haegel, Nancy M. "June 2008." Description based on title screen as viewed on August 26, 2008. Includes bibliographical references (p. 41-42). Also available in print.

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Zamani, Sahar. „Magnetic resonance imaging characterisation of water transport in cement-based materials“. Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606806.

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This work addresses a better understanding of water dynamics in cement paste and mortar materials. Permeability to water and water transport diffusion are measured using magnetic resonance profiling. Water self diffusion in one and two dimensions is measured using nuclear magnetic resonance pulsed field gradient diffusometry. With regard to water permeability of cement paste and mortars, three topics are addressed. The permeability is measured as a function of relative humidity for cement pastes of different sizes and as a function of sand size for mortars. The relative liquid water and water vapour permeability are calculated using a modified version of a model suggested by Barogbel-Bouny et aI.. The intrinsic permeability values for cement pastes are similar to those measured by beam bending methods by Vichit-Vadakan and Scberer The values found for mortars are similar to those measured by Baroghel-Bouny et at. The time dependence of the equilibration of the water concentration profile is also measured. With regard to water transport diffusion, mortars with different sand sizes are studied during water ingress/egress cycles. It is shown that ingress of water into dried mortars slows dramatically after some time most likely due to pore blocking by particulate fines carried with the water. Two indicative transport diffusion coefficients are obtained corresponding to the water diffusion before and after the blockage is encountered. With regard to diffusometry, the water self-diffusion coefficient was measured in a cement paste and found to decrease rapidly in the early stages of hydration. The capillary pore size distribution is measured from an analysis of restricted diffusion data in a mature sample. No evidence of capillary pore anisotropy is found

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Lauerer, Alexander, Philipp Zeigermann, Jörg Lenzner, Christian Chmelik, Rustem Valiullin und Jörg Kärger. „IR Micro-imaging of mesoporous silicon as a model system for the investigation of hysteresis phenomena“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183825.

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41

Xiao, Fanrong, Charles Nicholson und Sabina Hrabetova. „Anisotropic diffusion of flexible random-coil polymers measured in brain extracellular space by integrative optical imaging“. Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194244.

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42

Tao, Lian, Anna Tao, Robert G. Thorne und Charles Nicholson. „Integrative optical imaging of molecular diffusion in strong light scattering brain tissue“. Diffusion fundamentals 20 (2013) 78, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A12614.

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43

Nakagawa, Satoshi, Kazuyuki Chihara und Kuniyasu Ogawa. „2D Projective imaging of water concentration profiles in adsorption columns by MRI“. Diffusion fundamentals 16 (2011) 42, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13777.

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44

Freeman, Will. „Imaging transport : optical measurements of diffusion and drift in semiconductor materials and devices /“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FFreeman.pdf.

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45

Fraissard, Jacques. „NMR imaging as a tool for studying the diffusion and co-diffusion of gases in zeolite catalysts“. Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196370.

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1H NMR imaging is a powerful technique for studying the diffusion of pure hydrocarbons (for example benzene and n-hexane) during their adsorption in or desorption from a fixed bed of zeolite crystallites. This technique is used to visualize the progression of the diffusing molecules in the zeolite bed and to determine their intracrystallite diffusion coefficients. More importantly, NMR imaging is today the only technique able to give the time dependence of the distribution of two gases during their competitive diffusion.

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46

Elsner, Paul Heinrich. „Monitoring intertidal sedimentation dynamics using airborne imaging spectroscopy“. Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609749.

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47

Kossel, Elke, Christian Deusner, Nikolaus Bigalke und Matthias Haeckel. „Magnetic Resonance Imaging of gas hydrate formation and conversion at sub-seafloor conditions“. Diffusion fundamentals 18 (2013) 15, S. 1-4, 2013. https://ul.qucosa.de/id/qucosa%3A13724.

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The production of natural gas from sub-seafloor gas hydrates is one possible strategy to meet the world’s growing demand for energy. On the other hand, climate warming scenarios call for the substitution of fossil energy resources by sustainable energy concepts. Burning natural gas from gas hydrates could be emission neutral if it was combined with a safe storage of the emitted CO2. Laboratory experiments, that address corresponding strategies, need to be performed under high pressures and low temperatures to meet the thermodynamic conditions of the sub-seafloor environment. In this paper, we present a high-pressure flow-through sample cell that is suitable for nuclear magnetic resonance (NMR) experiments at realistic marine environmental conditions, i.e. pressures up to 15 MPa and temperatures from 5 to 20°C, and we demonstrate its suitability in applied gas hydrate research.

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48

Sigmund, Eric, Ravinder Regatte, Mark Schweitzer, Hyungjoon Cho und Yi-Qiao Song. „In vivo imaging of signal decay due to diffusion in the internal field in human knee trabecular bone“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192231.

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This study presents the first demonstration of the MR signal decay due to diffusion in the internal field (DDIF) for in vivo knee trabecular bone imaging. DDIF contrast was compared with high resolution FLASH, T1, and T2* mapping in healthy volunteers. DDIF maps showed spatial variation, superimposed on a T1 background, reflecting trabecular structure. DDIF and T2* maps showed correlated contrast near dense trabeculae, but their spatial textures differed, suggesting distinct structural sensitivities.

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49

Xiao, Fanrong, Charles Nicholson und Sabina Hrabetova. „Anisotropic diffusion of flexible random-coil polymers measured in brain extracellular space by integrative optical imaging: Anisotropic diffusion of flexible random-coil polymers measured inbrain extracellular space by integrative optical imaging“. Diffusion fundamentals 6 (2007) 83, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14262.

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50

Ramanan, Baheerathan. „Quantifying mass transport processes in environmental systems using magnetic resonance imaging (MRI)“. Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2974/.

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Understanding the transport behaviour of pollutants is key to enhance remediation strategies and to inform predictive models of pollutant behaviour in environmental and engineered systems. This work investigates magnetic resonance imaging (MRI) as a methodology for imaging heavy metal, molecular and nanoparticle transport in two different saturated porous systems: biofilms and saturated porous geologic media (gravel). While most renowned for its use in medicine, magnetic resonance imaging (MRI) is enabling us to image the transport of heavy metals, macro-molecules and nanoparticles inside biofilms and porous columns in real time. This is achieved using either ions which are paramagnetic (e.g. Cu2+) or molecules labelled with paramagnetic ions (e.g. Gd3+) or superparamagnetic (e.g. nanomagnetite) nanoparticles. Presence of these tracers causes a concentration dependent shortening of relaxation times (T1 or T2) of the surrounding 1H nuclei and thus creates noticeable changes in the MRI signal. Critically, this enables the transport of (super)paramagnetic ions, molecules or nanoparticles through the biofilm or porous geological media to be imaged. Moreover, the actual concentrations of molecules can be quantified, as changes in relaxation rates have a linear relationship with the concentration of the tracer molecules. Hence, MRI can be used not only to track but also to quantify the transport of (super)paramagnetic molecules inside biofilms and saturated porous columns. The key advantages of MRI over other techniques are its ability to image inside systems opaque to other methods and its ability to collect data non-invasively, hence the system is unperturbed by the analysis. In this study, the transport of Gd-DTPA, a commonly used MRI contrast agent, was successfully imaged through phototrophic biofilms of 10 and 2.5 mm thicknesses. To improve spatial resolution, for the 2.5 mm thickness biofilm, a bespoke 5 mm diameter RF coil was constructed. The comparison of spatially distributed, time-varying concentrations of Gd-DTPA inside the biofilms with diffusion models illustrated that transport was via both diffusion and advection. This work illustrated the potential of using paramagnetically labelled molecules to quantify molecular pollutant transport and fate in biofilms. MRI was also used to image heavy metal trasport in artificial biofilms (composed of agar and bacteria) to test the suitability of an existing adsorption-diffusion model to represent heavy metal transport and fate in biofilms. While the diffusion coefficients and adsorption constants estimated were appropriate, discrepancies between the model and the data illustrates models may need to be developed further to incorporate factors such as concentration dependant diffusion or cell lysis. Finally, the ability to image inside opaque systems was further exploited to image nanoparticle transport inside a coarse-grained packed column. This was undertaken to illustrate the potential for MRI to image nanoparticle pollutant transport in systems relevant to river beds and sustainable urban drainage systems (SUDS). MRI was successfully used to image the nanoparticle transport, with significant transport inhibition was observed in positively charged nanoparticles compared to negatively charged nanoparticles due to permanent attachment.

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