Charge and magnetic X-ray scattering

The hole doped transition metal oxides show remarkable properties that are related to the influence of charge and spin correlations. In this thesis charge correlations in hole doped manganite and nickelate systems are smdied using soft (˂2 keV), normal (10 keV) and high energy x-ray scattering (100 keV).The charge and J aim-Teller (JT) order is studied in the bi-layer manganite La(_2)-(_2r) Sr(_1)+(_2x)Mn(_2)O(_7) for x = 0.5, 0.55 and 0.60 using high energy x-ray scattering. In the x = 0.55 sample the charge ordered state existed in the same checkerboard pattern as observed in the x = 0.5 sample with no change in behaviour. However, in the x = 0.6 doped sample the charge ordered state entered a new regime characterised by incommensurate JT and charge order. The magnitude of the incommensurability was inversely proportional to the intensity of the JT and charge peaks. High resolution x-ray measurements of the charge stripe order in the La(_2-x)Sr(_x)NiO(_4) system in the doping range 0.20 ≤ x ≤ 0.50 are presented. As the doping was moved away in either direction from the commensurate x = 0.33 the charge stripes changed from a highly correlated state to an increasingly disordered charge glass state. At the commensurate 0.5 composition there was no increase in the intensity or correlation of the charge order despite a significantly higher transition temperature than in the lower doped compositions. Finally the first measurements of the orbital order in La(_0.5)Sr(_1.5) MnO(_4) using soft x-ray scattering at the manganese L edges are presented. The measurements directly probe the orbital order unlike the previously reported measurements at the manganese K-edge. Energy scans were carried out on the orbital order and compared with theoretical predictions. From this it was determined that both the Jahn-Teller distortions and direct orbital ordering contribute to the observed scattering

Using Noninvasive Brain Measurement to Explore the Psychological Effects of Computer Malfunctions on Users during Human-Computer Interactions

In today’s technologically driven world, there is a need to better understand the ways that common computer malfunctions affect computer users. These malfunctions may have measurable influences on computer user’s cognitive, emotional, and behavioral responses. An experiment was conducted where participants conducted a series of web search tasks while wearing functional nearinfrared spectroscopy (fNIRS) and galvanic skin response sensors. Two computer malfunctions were introduced during the sessions which had the potential to influence correlates of user trust and suspicion. Surveys were given after each session to measure user’s perceived emotional state, cognitive load, and perceived trust. Results suggest that fNIRS can be used to measure the different cognitive and emotional responses associated with computer malfunctions. These cognitive and emotional changes were correlated with users’ self-report levels of suspicion and trust, and they in turn suggest future work that further explores the capability of fNIRS for the measurement of user experience during human-computer interactions

Monitoring live fuel moisture using soil moisture and remote sensing proxies

Live fuel moisture (LFM) is an important fuel property controlling fuel ignition and fire propagation. LFM varies seasonally, and is controlled by precipitation, soil moisture, evapotranspiration, and plant physiology. LFM is typically sampled manually in the field, which leads to sparse measurements in space and time. Use of LFM proxies could reduce the need for field sampling while potentially improving spatial and temporal sampling density. This study compares soil moisture and remote sensing data to field-sampled LFM for Gambel oak (Quercus gambelii Nutt) and big sagebrush (Artemisia tridentata Nutt) in northern Utah. Bivariate linear regression models were constructed between LFM and four independent variables. Soil moisture was more strongly correlated with LFM than remote sensing measurements, and produced the lowest mean absolute error (MAE) in predicted LFM values at most of the sites. When sites were pooled, canopy water content (CWC) had stronger correlations with LFM than normalized difference vegetation index (NDVI) or normalized difference water index (NDWI). MAE values for all proxies were frequently above 20 % LFM at individual sites. Despite this relatively large error, remote sensing and soil moisture data may still be useful for improving understanding of spatial and temporal trends in LFM

The Immediacy Of Linguistic Computation

This dissertation investigates the wide-ranging implications of a simple fact: language unfolds over time. Whether as cognitive symbols in our minds, or as their physical realization in the world, if linguistic computations are not made over transient and shifting information as it occurs, they cannot be made at all. This dissertation explores the interaction between the computations, mechanisms, and representations of language acquisition and language processing—with a central theme being the unique study of the temporal restrictions inherent to information processing that I term the immediacy of linguistic computation. This program motivates the study of intermediate representations recruited during online processing and acquisition rather than simply an Input/Output mapping. While ultimately extracted from linguistic input, such intermediate representations may differ significantly from the underlying distributional signal. I demonstrate that, due to the immediacy of linguistic computation, such intermediate representations are necessary, discoverable, and offer an explanatory connection between competence (linguistic representation) and performance (psycholinguistic behavior). The dissertation is comprised of four case studies. First, I present experimental evidence from a perceptual learning paradigm that the intermediate representation of speech consists of probabilistic activation over discrete linguistic categories but includes no direct information about the original acoustic-phonetic signal. Second, I present a computational model of word learning grounded in category formation. Instead of retaining experiential statistics over words and all their potential meanings, my model constructs hypotheses for word meanings as they occur. Uses of the same word are evaluated (and revised) with respect to the learner\u27s intermediate representation rather than to their complete distribution of experience. In the third case study, I probe predictions about the time-course, content, and structure of these intermediate representations of meaning via a new eye-tracking paradigm. Finally, the fourth case study uses large-scale corpus data to explore syntactic choices during language production. I demonstrate how a mechanistic account of production can give rise to highly efficient outcomes even without explicit optimization. Taken together these case studies represent a rich analysis of the immediacy of linguistic computation and its system-wide impact on the mental representations and cognitive algorithms of language

Poly(N-isopropylacrylamide) hydrogels for storage and delivery of reagents to paper-based analytical devices

The thermally responsive hydrogel N,N\u27-methylenebisacrylamide-cross-linked poly(N-isopropylacrylamide) (PNIPAM) was developed and evaluated as a reagent storage and delivery system for microfluidic paper-based analytical devices (microPADs). PNIPAM was shown to successfully deliver multiple solutions to microPADs in specific sequences or simultaneously in laminar-flow configuration and was found to be suitable for delivering four classes of reagents to the devices: Small molecules, enzymes, antibodies and DNA. PNIPAM was also able to successfully deliver a series of standard glucose solutions to microPADs equipped to perform a colorimetric glucose assay. The results of these tests were used to produce an external calibration curve, which in turn was used to determine the concentration of glucose in sample solutions. Finally, PNIPAM was used to store the enzyme horseradish peroxidase for 35 days under ambient conditions with no significant loss of activity. The combination of PNIPAM and microPADs may allow for more complex assays to be performed on paper-based devices, facilitate the preparation of external calibration curves in the field, and extend the shelf life of microPADs by stabilizing reagents in an easy-to-use format

Giant mesenteric lymphatic malformation presenting as small bowel volvulus

Abdominal pain with bilious emesis is an ominous clinical presentation with many possible causes. We describe a previously healthy 4-year-old boy who presented with these symptoms and ultrasound findings of fluid throughout most of the abdominal cavity. Computed tomography imaging revealed a large cystic mass (21-by-13 cm) associated with a small bowel obstruction due to volvulus. A laparoscopic exploration was undertaken, revealing a large mass arising from the small intestinal mesentery and causing a segmental volvulus of the small bowel. Conversion to mini-laparotomy allowed reduction of the volvulus and segmental resection of the small bowel associated with a giant mesenteric lymphatic malformation. This case describes a rare cause of intestinal volvulus due to a mesenteric lymphatic malformation