Abstract The x~ 1/8anomaly in the La-based cuprates had been puzzling since the discovery of high-Tc superconductors. Recently, the stripe phase which has attracted considerable attention in connection with many experiments, like neutron scattering, Raman and infrared(IR) spectra, Hall effect, thermoelectric power and magnetic susceptibility, etc. These results indicate that a crossover from one- to two-dimensional charge transfer accurs at x~1/8 . In this thesis, we synthesize two series of p-type superconductors La2-xSrxCuO4 and La1.4-xSrxNd0.6CuO4 by solid-state reaction. It has been well known that there is a marked drop in Tc - x phase diagram at x~1/8 in both systems. It is possible that this phenomenon is related to the stripe phase. This interesting question has motivated us to initiate the experiment of x-ray absorption near edge spectroscopy (XANES) to investigate the possibility of the electronic structure change caused by the stripe phase. It is found that the spectral weight of the hole carriers scales with the doping level x rather than with Tc . However, the charge stripe was observed in La1.4-xSrxNd0.6CuO4, but not in La2-xSrxCuO4. Our results also suggest that the formation of the stripe phase is not related to the structural phase transition in La1.4-xSrxNd0.6CuO4 consistent with earlier results. Comparisons are made between our results and those reported on the basic of the stripe phase scenario.

Thesis (M.S. in plant pathology)--Washington State University, December 2008. / Title from PDF title page (viewed on Sept. 23, 2008). "Department of Plant Pathology." Includes bibliographical references.

Thesis (M.S.)--Washington State University, May 2006. / Includes bibliographical references.

In this thesis, we study stripe states in underdoped cuprate superconductors using the Bogoliubov-de Gennes (BdG) method with appropriate models. In non-self-consistent calculations, the nature of stripe states with coexisting unidirectional Pair Density Wave (PDW), Charge Density Wave (CDW), and Spin Density Wave(SDW) order is studied, and it was found that among these coexisting stripe orders, the SDW order plays a key role in reconstructing the Fermi Surface (FS), and the magnitude of SDW order needs to be relatively small in order for Fermi arcs to be realized, while strong SDW order necessarily leads to completely gapped spectra. In self-consistent calculations, we mapped out parameter regions where stripe SC states can be stabilized, which are in qualitative agreement with the generic phase diagram of cuprate superconductors. In addition, self-consistent PDW solutions with small SDW order are stabilized in some parameter region, forming small FS pockets in antinodal regions. This parameter region is a promising one to explore in future work, where self-consistent BdG calculation is to be carried out with a magnetic field in order to study the effect of magnetic field on the stability of stripes along with the possible quantum oscillations. / Thesis / Master of Science (MSc)

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This thesis describes the background, investigation and construction of a system for storing data on the magnetic stripe of a standard three-inch plastic credit in: inch card. Investigation shows that the information storage limit within a 3.375 in by 0.11 in rectangle of the stripe is bounded to about 20 kBytes. Practical issues limit the data storage to around 300 Bytes with a low raw error rate: a four-fold density increase over the standard. Removal of the timing jitter (that is prob-' ably caused by the magnetic medium particle size) would increase the limit to 1500 Bytes with no other system changes. This is enough capacity for either a small digital passport photograph or a digitized signature: making it possible to remove printed versions from the surface of the card. To achieve even these modest gains has required the development of a new variable rate code that is more resilient to timing errors than other codes in its efficiency class. The tabulation of the effects of timing errors required the construction of a new code metric and self-recovering decoders. In addition, a new method of timing recovery, based on the signal 'snatches' has been invented to increase the rapidity with which a Bayesian decoder can track the changing velocity of a hand-swiped card. The timing recovery and Bayesian detector have been integrated into one computation (software) unit that is self-contained and can decode a general class of (d, k) constrained codes. Additionally, the unit has a signal truncation mechanism to alleviate some of the effects of non-linear distortion that are present when a magnetic card is read with a magneto-resistive magnetic sensor that has been driven beyond its bias magnetization. While the storage density is low and the total storage capacity is meagre in comparison with contemporary storage devices, the high density card may still have a niche role to play in society. Nevertheless, in the face of the Smart card its long term outlook is uncertain. However, several areas of coding and detection under short-duration extreme conditions have brought new decoding methods to light. The scope of these methods is not limited just to the credit card.

Disease has been implied as an important selective force acting in plant populations. This study was conducted to determine the effects of stripe rust (Puccinia striiformis) on the population dynamics of wheat (Triticum aestivum) cultivar mixtures. Five wheat cultivars were grown in pure stands and all possible mixtures at three and two locations in 1987 and 1988, respectively. In 1989, four replacement series and their component pure stands were grown in two locations. All treatments were exposed to or protected from two stripe rust races. Disease severity and yield were determined on a per-cultivar basis for mixtures and also for pure stands. In all but one mixture, disease severity relative to the pure stands was reduced between 6 and 97%. Disease severity changes could be separated into two effects: First, selection for the more resistant or susceptible genotype reduced or increased disease in mixtures as compared to their pure stands by up to 47 and 11%, respectively. Second, epidemiological effects of host diversity reduced disease severity on individual cultivars below that of their pure stands. Disease severity on a genotype was often frequency-dependent. However, interactions among plant genotypes sometimes appeared to alter susceptibility and obscured the relationship. Non-diseased and diseased mixtures yielded 0 to 8% and 8 to 15% more than pure stands, respectively. overall, mixture yields were more influenced by plant-plant interactions than by disease. Population dynamics over time were studied by applying variable disease pressure to populations of four wheat cultivars for one-to-three generations in two locations. Fitnesses of genotypes were calculated by regressing the legit of a genotype's frequency on generation. Fitnesses were affected by disease and location and appeared constant over time. However, genotype frequency-changes were negatively correlated with planting frequencies, suggesting that fitnesses were frequency-dependent. Analysis of data from longer-term studies in the literature indicated that three generations may not have been sufficient to detect frequency-dependence. Stable equilibria may more likely exist for mixtures of genotypes that are closely related and adapted to the environment in which they are grown than for randomly selected genotypes. / Graduation date: 1992

EXtensible Markup Language, XML, was designed as a markup language for structuring, storing and transporting data on the World Wide Web. The focus of XML is on data content; arbitrary markup is used to describe data. This versatile, self-describing data representation has established XML as the universal data format and the de facto standard for information exchange on the Web. This has gradually given rise to the need for efficient storage and querying of large XML repositories. To that end, we propose a new model for building a native XML store which is based on a generalisation of vertical decomposition. Nodes of a document satisfying the same label-path, are extracted and stored together in a single container, a Stripe. Stripes make use of a labelling scheme allowing us to maintain full structural information. Over this new representation, we introduce various evaluation techniques, which allow us to handle a large fragment of XPath 2.0. We also focus on the optimisation opportunities that arise from our decomposition model during any query evaluation phase. During query validation, we present an input minimisation process that exploits the proposed model for identifying input that is only relevant to the given query, in terms of Stripes. We also define query equivalence rules for query rewriting over our proposed model. Finally, during query optimisation, we deal with whether and under which circumstances certain evaluation algorithms can be replaced by others having lower I/O and/or CPU cost. We propose three storage schemes under our general decomposition technique. The schemes differ in the compression method imposed on the structural part of the XML document. The first storage scheme imposes no compression. The second storage scheme exploits structural regularities of the document to minimise storage and, thus, I/O cost during query evaluation. Finally, the third storage scheme performs structureagnostic compression of the document structure which results in minimised storage, regardless the actual XML structure. We experiment on XML repositories of varying size, recursion and structural regularity. We consider query input size, execution plan size and query response time as metrics for our experimental results. We process query workloads by applying each of the proposed optimisations in isolation and then all of their combinations. In addition, we apply the same execution pipeline for all proposed storage schemes. As a reference to our proposed query evaluation pipeline, we use the current state-of-the-art system for XML query processing. Our results demonstrate that: • Our proposed data model provides the infrastructure for efficiently selecting the parts of the document that are relevant to a given query. • The application of query rewriting, combined with input minimisation, reduces query input size as well as the number of physical operators used. In addition, when evaluation algorithms are specialised to the decomposition method, query response time is further reduced. • Query evaluation performance is largely affected by the storage schemes, which are closely related to the structural properties of the data. The achieved compression ratio greatly affects storage size and therefore, query response times.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 58-68). Also available on the World Wide Web.

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