Restaurierung von kohärenten Bildern

In this thesis a series of novel algorithms for high quality restoration of coherent images is introduced. This task cannot be solved with established methods for the restoration of incoherent images. These algorithms focus on the correction of images in coherent imaging systems with a-priori known aberrations. The new wavefront correction algorithms achieve a significantly higher restoration quality than any previously known technique. The algorithms in this thesis are based on latest advances in optimization algorithms, particularly projections onto convex sets, proximal optimization and fractal self-similarity. Convergence and performance of the individual algorithms are analyzed in detail in various scenarios on real and simulated images. The evaluation also deals with the impact of noise on the restoration quality. Practical application of the new algorithms on microscopic images of diverse biological and human samples, as well as shadowgraph images of plankton acquired with a laboratory setup prove their efficiency. The new algorithms also have promising future applications in other areas, for example in adaptive optics and astronomy.In dieser Thesis werden mehrere neue Algorithmen für eine qualitativ hochwertige Restaurierung von kohärenten Bildern vorgestellt. Diese Aufgabe kann mit den bekannten Methoden für die Restaurierung von nicht kohärenten Bildern nicht gelöst werden. Die neuen Algorithmen sind auf die Wiederherstellung von Bildern in kohärenten Abbildungssystemen, bei denen die Aberrationen a-priori bekannt sind, ausgerichtet. Sie dienen der Korrektur der Wellenfront und erreichen eine wesentlich höhere Qualität der Bildrekonstruktion als sämtliche vorbekannte Verfahren. Die Algorithmen in dieser Thesis basieren auf neuesten Optimierungsalgorithmen, wie Projektionen in konvexe Sets, proximale Optimierung und fraktaler Ähnlichkeit. Die Konvergenz und Leistung der einzelnen Algorithmen wird ausführlich in unterschiedlichen Szenarien mit simulierten und realen Bildern untersucht. Eine praktische Erprobung der neuen Algorithmen an mikroskopischen Aufnahmen von unterschiedlichen biologischen und humanen Proben, wie auch an Aufnahmen vom Shadowgraph, bestätigt ihre Effizienz. Die neuen Algorithmen haben vielversprechende künftige Anwendungen, auch in anderen Gebieten, z.B. in der adaptiven Optik und der Astronomie

Digital In-Line Holography for Large-Volume Analysis of Vertical Motion of Microscale Marine Plankton and Other Particles

Acknowledgements This work is funded by a joint UK-Japan research program (NERC-JST SICORP Marine Sensor Proof of Concept under project code NE/R01227X/1). The authors would like to thank the captain, crew, science party and technical support staff of the R/V Yokosuka cruise YK20-E02. We also thank Dr. Y. Nagai for providing us the foraminifera samples.Peer reviewedPostprin

Holographic Particle Image Velocimetry of Ink Jet Streams

Ink jet technology is a rapidly growing and diverse field of research. Ink jets are used to deliver very precise and small (picolitre) volumes of fluid to a surface. Recent advances in ink jet technology demand a better understanding of the dynamics of the fluid during jetting. The aim of this project was to design a method capable of measuring the flow velocities inside ink jet streams. This objective has been achieved by the use of digital holographic particle image velocimetry. The difficulty with measuring flows inside tightly curved samples is that the refractive index change over the boundary leads to an optical distortion and therefore particles cannot be viewed or tracked reliably. Optical distortion is compensated for by taking advantage of the ability to replay a holographically recorded wave. The light scattered by particles is propagated numerically back through the sample’s surface, to form a three-dimensional image in which all refractions at the interface have been accounted for. Three dimensional particle fields are then analysed using custom particle detection and correlation code to extract the displacement of individual particles between exposures, which facilitates the construction of full flow profiles. Holograms were recorded with a simple off-axis holographic microscope, comprising two point sources of divergent light, formed from the same objective lens, acting as the source of illumination and reference light, respectively. Experiments were conducted on continuous ink jet streams of water issuing from a nozzle with 100 µm diameter. For a few millimetres after the nozzle exit, the jet is cylindrical, it then starts to form swells and necks; the swells continue to grow at the expense of the necks until the jet breaks up into a stream of droplets. Measurements of the stream wise component of velocity have been successful in the cylindrical parts of the jet, in swells and in necks greater than 20 µm in diameter. To my knowledge measurements of particle velocities on fluid jets at this scale have not been accomplished previously

Influence of Regional Oceanography on the Distributions, Trophic Interactions, Growth, and Survival of the Early Life History Stages of Fishes

Most marine fishes experience high rates of mortality during their early life history stages with far reaching consequences for adult population dynamics. Within a few weeks of hatching, relatively small changes in larval growth and mortality rates can lead to orders of magnitude variability in year-class strength. Growth and survival during this phase are contingent upon the ability of larvae to find food and avoid predation in a physically and biologically heterogeneous environment. Here, we coupled biological sampling and fine-scale in situ plankton imaging to examine the influence of regional oceanography on larval fish distributions, feeding, and growth in the context of their zooplankton prey and predators in the northern California Current (NCC). Larval fish were strongly affected by two highly dynamic regional oceanographic features in the NCC: coastal upwelling and the Columbia River Plume. While the NCC supports major fisheries whose larval and juvenile stages depend on upwelling driven primary and secondary production, coastal upwelling is highly variable in space and time. In Chapter 2, diet and otolith microstructure analysis showed that the condition of a dominant myctophid (Stenobrachius leucopsarus) reflected the prevailing upwelling conditions. During reduced upwelling, recent growth was substantially slower, guts less full, and diets dominated by low trophic level prey. In contrast, during active upwelling, faster-growing northern lampfish fed on higher quality copepod prey. Yet, larvae exhibited reduced feeding and growth in the most intense upwelling, revealing a dome-shaped relationship with the fastest growth occurring in moderate upwelling conditions. Further, high zooplanktivorous predation pressure on larval northern lampfish led to above average growth, which may indicate the selective loss of slower-growing larvae. Chapter 3 revealed that upwelling also influenced the larval growth of another forage fish, northern anchovy (Engraulis mordax). Northern anchovy otolith-derived recent growth was spatially variable and related to the location of the summer upwelling front. When the front was restricted nearshore, inshore larval anchovy grew significantly faster than offshore. Conversely, when a period of prolonged active upwelling pushed the front to the edge of the continental shelf, offshore anchovy larvae grew significantly faster than inshore. Larval anchovy growth may be constrained by cross-shelf temperature differences and the distribution of nutritious copepod prey that are restricted to the nearshore environment off Oregon in summer. Embedded within the highly dynamic NCC, the tidally modulated Columbia River Plume is an important spawning and nursery ground for many fishes (e.g., northern anchovy, E. mordax). In Chapter 4, data illustrated how the strength and location of the plume front exposed larval fishes to a diversity of unique prey and predator fields over the progression of a tidal cycle. While the plume region provided a substantially higher concentration of prey that are important for the feeding of young fishes occupying this area, this region was also characterized by enhanced spatial overlap of larval fishes and their zooplankton predators relative to oceanic waters. In a separate study, and in partial fulfillment of the National Science Foundation Research Traineeship (NRT) program at Oregon State University, Chapter 5 switched focus from larval fishes to another component of the plankton: Dungeness crab larvae. Mortality during the early life history stages of Dungeness crab is considered a bottleneck for fishery production, but information on the offshore distribution of the most vulnerable pelagic larval stages is lacking. Fine-scale depth discrete biological sampling over two years revealed that Dungeness crab larvae were not uniformly distributed in time or space, but exhibited distinct spatial distributions within the water column, over the continental shelf, and across latitudes, with larval abundance significantly negatively correlated with in situ temperature and salinity throughout ontogeny. Taken together, this body of work demonstrates that local and regional oceanographic features contribute to variable zooplankton distributions as well as growth and mortality patterns for larval fishes by affecting their trophic interactions. This dissertation illustrates the importance of incorporating food-web dynamics and local and regional oceanographic processes when predicting the response of fish and crab populations to ecosystem variability

Research and Technology, 1989

Selected research and technology activities at Ames Research Center, including the Moffett Field site and the Dryden Flight Research Facility, are summarized. These accomplishments exemplify the Center's varied and highly productive research efforts for 1989

Turbulent structure in environmental flows: effects of stratification and rotation

Several series of experiments in stratified and in rotating/stratified decaying flows after a grid is used to stir the two layer stable fluid brine and fresh water set up. We measure by comparing the gained potential energy with the available kinetic energy AKE, the relative efficiency of mixing. The experiments in stratified rotating flows with grid driven turbulence were both periodic (quasi stationary) and non-monotonic (decaying) forcing. This thesis compares experimental, numerical and field observations on the structure and Topology of the Stratified Rotating Flows as well as their decay, the horizontal spectra changes appreciable with slopes from 1.1 to 5, but vorticity and local circulation, and also the initial topology and forcing of the flow. A detailed study of the vorticity decay and vortex and energy structure has been performed, the new results show that neither stratified nor rotating flows exhibit pure 2D structures. The work parameterizes the role of the Richardson number and the Rossby number, both in the experiments and in the ocean visualizations is very important. The conditions of vortex decay show the effects of the internal waves in the decay turbulent conditions both for stratified and rotating flows. The parameter space (Re,Ri,Ro) has been used to interpret many previously disconnected explanations of the 2D-3D turbulent behaviour. The comparison of numerical simulations with experiments has allowed implementing new theoretical aspects of the interaction between waves and vortices finding the surprising and very interesting result that these interactions depend on the level of enstrophy. This also leads to new ways of using multifractal analysis ad intermittency in ocean environmental observations. A large collection of SAR images obtained from three European coastal areas were used for routine satellite analysis by SAR and other sensors, which seem very important to build seasonal databases of the dynamic conditions of ocean mixing. The topology of the basic flow is very important and in particular the topology of the vortices and their decay which depends on ambient factors such as wave activity, wind and currents. We find more realistic estimates of the spatial/temporal non-homogeneities (and intermittency obtained as spatial correlations of the turbulent dissipation); these values are used to parameterize the sea surface turbulence, as well as a laboratory experiments at a variety of scales. Using multi-fractal geometry as well, we can establish now a theoretical pattern for the turbulence behaviour that is reflected in the different descriptors. Vorticity evolution is smoother and different than that of scalar or tracer density. The correlation between the local Ri and the fractal dimension detected from energy or entropy is good. Using multi-fractal geometry we can also establish certain regions of higher local activity used to establish the geometry of the turbulence mixing that needs to be studied in detail when interpreting the complex balance between the direct 3D Kolmogorov type cascade and the Inverse 2D Kraichnan type cascade

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals