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High Contrast Imaging of Planet-forming Disks with Extreme Adaptive Optics Systems
Get PDFCircumstellar disks serve as benchmark systems to study how and where exoplanets form. With the advent of ground-based extreme adaptive optics (AO) facilities, we have entered a revolutionary era for disk studies. It is now feasible to simultaneously resolve the structures within disks that could be caused by planets and directly identify the young companions that may induce them. The use of integral field spectrographs (IFSs) --- which provide images at an array of wavelengths --- enhances this capability by helping to characterize disk material and any identified companions.
Using data from Subaru's extreme AO system, SCExAO, paired with the CHARIS IFS, we present near-infrared (NIR) observations of two systems hosting debris disks --- gas-poor, dusty disks at the end stages of planetary system formation. For HD 15115, we introduce the use of differential evolution (DE) for disk model optimization --- which finds a strong solution while evaluating many fewer models than common alternatives. From modeling, we find no evidence to support the presence of a (possibly planet-driven) misaligned inner-ring as was suggested previously. For the HD 36546 system, we show its disk has either an extremely shallow radial density profile or a ``back-swept wing profile"; the latter case, combined with the blue NIR color of the disk, could suggest interaction with an unseen planet.
CHARIS recently added a new and unique integral field spectropolarimetry mode which produces high-contrast polarimetry at the same array of wavelengths as its standard IFS mode. We describe the software module which we designed to process data from this observing mode, present preliminary results for two planet-forming disk systems, and provide a summary of investigations enabled by this mode --- including tests on embedded companions.
Finally, we introduce a new technique for removing starlight in imagery of circumstellar disk systems, ``Constrained Reference Star Differential Imaging (RDI)", which uses prior knowledge to more accurately model (and remove) the starlight in a data sequence. Using simulated and on-sky data, we demonstrate the ability of this technique to effectively eliminate the variable loss of circumstellar light that normally occurs as starlight is removed. This enables spatial and spectral analysis of circumstellar disks in unprecedented detail and provides a much clearer path to the robust identification and validation of exoplanets embedded within them
Influence of Interfacial Rheological Properties on the Stability of Pickering Foams
Get PDFThis work is aimed at gaining a fundamental understanding of the role of interfacial
phenomena in foam stability. We have investigated the properties of Pickering foams,
stabilized with fumed and spherical colloidal silica nanoparticles, and studied the impacts
of particle attributes on the resulting properties such as bubble microstructure, foam liquid
content, and foam half – life. We have examined the microstructure of analogue particle –
laden interfaces and probed their response to applied deformations via both interfacial
dilatational and shear rheology measurements. While the overall foam heights and
microstructure remain similar for both particle types used, differences are observed in their
interfacial shear and dilatational rheological measurements. Foams stabilized with fumed
silica particles are able to resist liquid drainage to a higher degree, as captured by a
plateaued reduced osmotic pressure over time, whereas the reduced osmotic pressure for
the spherical particle – stabilized foams increased slowly over time. With regards to
rheology, the interfacial network formed by spherical silica particle had slightly larger
values of elastic moduli (’) than the fumed silica network. However, interfaces coated
with fumed silica particles, undergoing dilational deformations, retained a particle network
over a broader range of dilational strain compared to spherical particles. In shear mode, the
interfacial networks formed by the spherical particles have higher storage moduli (’)
compared to those obtained from fumed particles, whereas the critical shear strain
corresponding to the yield point is larger for the fumed particle networks. Our findings
demonstrate that while both fumed and spherical silica particles are able to stabilize the
air/water interface and make long – lasting foams, the resulting Pickering foams are
markedly different with respect to their network properties and resistance to various
destabilization mechanisms
Electrophysiological resting state brain network and episodic memory in healthy aging adults
Get PDFRecent studies have emphasized the changes in large-scale brain networks related to healthy aging, with the ultimate purpose to aid in differentiating normal neurocognitive aging from neurodegenerative disorders that also arise with age. Emerging evidence from functional Magnetic Resonance Imaging (fMRI) indicates that connectivity patterns within specific brain networks, especially the Default Mode Network (DMN), distinguish those with Alzheimer's disease from healthy individuals. In addition, disruptive alterations in the large-scale brain systems that support high-level cognition are shown to accompany cognitive decline at the behavioral level, which is commonly observed in the aging populations, even in the absence of disease. Although fMRI is useful for assessing functional changes in brain networks, its high costs and limited accessibility discourage studies that need large populations. In this study, we investigated the aging-effect on large-scale networks of the human brain using high-density electroencephalography and electrophysiological source imaging, which is a less costly and more accessible alternative to fMRI. In particular, our study examined a group of healthy subjects in the age range from middle- to older-aged adults, which is an under-studied range in the literature. Employing a high-resolution computation model, our results revealed age associations in the connectivity pattern of DMN in a consistent manner with previous fMRI findings. Particularly, in combination with a standard battery of cognitive tests, our data showed that in the posterior cingulate / precuneus area of DMN higher brain connectivity was associated with lower performance on an episodic memory task. The findings demonstrate the feasibility of using electrophysiological imaging to characterize large-scale brain networks and suggest that changes in network connectivity are associated with normal aging.This study was supported by National Science Foundation RII Track-2 FEC 1539068, Oklahoma Center for the Advancement of Science & Technology HR16–057, and Institute for Biomedical Engineering, Science, and Technology at University of Oklahoma. Financial support was provided by the University of Oklahoma Libraries’ Open Access Fund.Ye
Optimal Selection of Short-and Long-Term Mitigation Strategies for Buildings within Communities under Flooding Hazard
Get PDFEvery year, floods cause substantial economic losses worldwide with devastating impacts on buildings and physical infrastructures throughout communities. Techniques are available to mitigate flood damage and subsequent losses, but the ability to weigh such strategies with respect to their benefits from a community resilience perspective is limited in the literature. Investing in flood mitigation is critical for communities to protect the physical and socioeconomic systems that depend on them. While there are multiple mitigation options to implement at the building level, this paper focuses on determining the optimal flood mitigation strategy for buildings to minimize flood losses within a community. In this research, a mixed integer linear programming model is proposed for studying the effects and trade-offs associated with pre-event short-term and long-term mitigation strategies to minimize the expected economic losses associated with floods. The capabilities of the proposed model are illustrated for Lumberton, North Carolina (NC), a small, socially diverse inland community on the Lumber River. The mathematically optimal building-level flood mitigation plan is provided based on the available budget, which can significantly minimize the total expected direct economic loss of the community. The results reveal important correlations among investment quantity, building-level short- and long-term mitigation measures, flood depths of various locations, and buildings’ structure. Additionally, this study shows the trade-offs between short- and long-term mitigation measures based on available budget by providing decision support to building owners regarding mitigation measures for their buildings.This research was partially funded by the National Institute of Standards and Technology (NIST) Center of Excellence for Risk-Based Community Resilience Planning through a cooperative agreement with Colorado State University [70NANB20H008 and 70NANB15H044]. This research was also partially funded by the National Science Foundation (NSF) through award 2052930. Article processing charge was partially provided by the University of Oklahoma Libraries’ Open Access Fund.Ye
Development and characterization of injectable biocompatible hyaluronic acid hydrogels for potential brain aneurysm blockage and vascular regeneration
No full textBrain aneurysms are blood vessel wall deformations that affect 240 million people worldwide and their rupture causes the death of a fourth of the patients each year. Current brain aneurysm treatments, like surgical clips or coils, allow only partial aneurysm occlusion and partial blood vessel wall reconstruction. These treatments stay in the patient ad vitam, thus having a high risk of causing vessel wall inflammation. To address these issues, our approach is catheter-based delivery of an injectable, hyaluronic acid-based material that is compatible with radiographic and magnetic resonance medical imaging techniques. This material can be used to plug saccular brain aneurysms and induce vascular regeneration. To make our PHA hydrogels visible via brain imaging techniques to assess correct delivery and provide a control of the aneurysm degradation overtime, 50 mg/mL of tantalum powder (Ta) was incorporated to PHA hydrogels. To assess whether PHA hydrogel matches the compressive resistance of vessel walls, compressive moduli of 5, 7.5, and 10% PHA hydrogels without or with 50 mg of Ta per g of PHA were measured. The compressive moduli of 5, 7.5, and 10% PHA hydrogels without or with 50 mg of Ta per g of PHA increased with weight percent and were comprised within a 50 to 100 kPa range, which is the range of brain tissues’ compressive moduli. To verify the biocompatibility of PHA hydrogels with blood vessels, the cell viability of human umbilical vein endothelial cells (HUVEC) in contact with medium infused for 24 hours with 5, 7.5, and 10% PHA hydrogels without or with 50 mg of Ta per g of PHA was quantified. The viability of HUVEC exposed to 5, 7.5, and 10% PHA hydrogels without or with 50 mg of Ta per g of PHA was a 100%. These data point out that injectable 5 and 7.5% PHA hydrogels with compressive moduli similar to brain tissues and good viability with endothelial cells can be made to potentially plug brain aneurysms
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No full textAerial photograph index (photomosaic), Grant County Oklahoma. MAP 4 of
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No full textAerial photograph index (photomosaic), Hughes Co. OKLA. -AWH- MAP 6 of
Development of Novel Material Design Strategies for High-Efficiency and Tunable Photoluminescence Properties
Get PDFNew developments in the understanding of structural-optical property relationships of optoelectronic materials have led to rapid growth in energy-efficient solid-state lighting technologies. These improvements in the field of inorganic materials chemistry have led to new products, such as light-emitting diodes (LEDs) for residential lighting, scintillators for radiation detection, and luminescent inks for anti-counterfeiting applications. The emergence of lead halide perovskites has led to a paradigm shift in this area, with many groups around the globe working on both fundamental properties and practical applications of this diverse family. An unexplored alternative to the toxic nature of lead halides is the recently discovered families of earth-abundant and non-toxic copper(I) and silver halides. The structural-optical property relationships and physical properties of these new materials must be elucidated to continue development. This work focuses on understanding the optoelectronic properties of copper(I) and silver halides. The work also explores the strategy of utilizing organic cations as the source of emission, as opposed to more popular reliance on the metal halide polyhedra.
To better understand the history and fundamental science, the work begins with an introduction to down-converting metal halides in chapter 1. The information presented in the first chapter directly applies to the following chapter, as chapter 2 continues by investigating A2CuX3 (A= K, Rb and X= Cl, Br), a family of bright blue photoluminescent compounds with up to unity absolute photoluminescent quantum yield. A series of optical measurements were completed in order to thoroughly examine the effects of elemental substitution. The optical measurements were also supported with additional chemical purity and environmental stability test. The emission mechanism in these materials is established through a combination of spectroscopic and computational studies.
While the all-inorganic copper(I) halides answered some questions, many more were asked upon completion of the work. To further explore the impact of substituting the metal center, chapter 3 dives into the analogous silver halides in hopes of better understanding the varying emission mechanisms that can exist in these systems. These compounds display tunable, white emission, in stark contrast to their copper(I) counterparts. A broader elemental substitution study was conducted to understand the role of vacancies in the system. The work progressed beyond fundamental material design and continued into preliminary application research.
While extensive investigations of crystal and electronic structures and optical properties of all-inorganic group 11 metal halides have been conducted, a vast family of hybrid Cu(I) and Ag(I) materials remains unexplored. The last research component, chapter 4, changes directions away from metal-derived emission and explores the area of organic-derived emission. Although many organic compounds are known to be efficient light emitters, they are often unstable for practical application considerations. This work evaluates a novel method to stabilize and improve the photoluminescent emission while maintaining the same emission profile. The work opens the door to more hybrid organic-inorganic emitters. To tie everything together, chapter 5 concludes the work and discusses future directions
Settling in at the Cross Bar Ranch: Antelope Creek Settlement Patterns and Distributions in the Texas Panhandle
Get PDFPrevious research conducted by Dr. Christopher Lintz into the settlement patterning of Antelope Creek groups in the southern Great Plains found that those settlements could be typified according to their site function, and further delineated through specific environmental preferences and architectural styles. The purpose of this examination is to assess the validity of Lintz’s Antelope Creek settlement model using more recent spatial statistics and other GIS analyses, while also testing his model within a study area different from his own. Specifically investigated is the relationship between various sites and their local ecological preferences, as well as plausible associations between sites sharing a close proximity. In particular, environmental elements such as elevation, degree of slope, distance and access to potable water, flora/fauna diversity, soil composition, and topographic setting are compared between Lintz’s site typologies of subhomesteads and homesteads within an area of the Texas panhandle known as the Cross Bar Ranch
LGBQ Identity and E-cigarette Dependence Among Young Adults
Get PDFIntroduction: E-cigarette use is most prevalent among young adults (18-25-year-olds) and lesbian, gay, bisexual, and queer (LGBQ) people when compared to other age groups and heterosexual people. This study examined the relationship between LGBQ identity and e-cigarette dependence in LGBQ young adults.
Methods: Using the Lesbian, Gay, and Bisexual Identity Scale (LGBIS) subscales to assess LGBQ identity and the Penn State Electronic Cigarette Dependence Index (PSECDI) to assess dependence, different aspects of LGBQ identity were measured and analyzed using multiple linear regression to reveal their association with e-cigarette dependence in a sample (N=242) of LGBQ young adults who vaped and owned an e-cigarette at the time of the study. The study was cross-sectional, and responses were recorded via an online survey.
Results: Identity Superiority was found to be significantly and positively associated with dependence (β = .227, p = .017), and Identity Centrality was found to be significantly and negatively associated with dependence (β = -.320, p = .005). The other LGBIS subscales were not found to be significantly associated with dependence.
Conclusions: This study was the first to use the LGBIS and the PSECDI in conjunction to analyze e-cigarette dependence and LGBQ identity among young adult LGBQ people. It identified two aspects of LGBQ identity that were significantly associated with dependence