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21-cm Cosmology and Low-Frequency Radio Astronomy from the Moon
Full text link21-cm cosmology concerns itself with the last, unmeasured epochs of the Universe, between the decoupling of the CMB and the end of Reionization in particular. These epochs include the cosmic Dark Ages, before any luminous astrophysical structures had formed, Cosmic Dawn, when the first sources and galaxies appeared, and the Epoch of Reionziation, when they reionized the intergalactic medium. By measuring the hyperfine, highly redshifted 21-cm line of neutral Hydrogen during these epochs, it is possible to map the thermal and ionization state of the entire Universe, describe the first sources, map structure formation, and even test dark matter and cosmology models in unique ways and epochs, such as during the Dark Ages. Formidable systematics, however, must be removed before an unambiguous detection is made. In this thesis we present novel models, statistical tests, and analyses for two of the primary systematics, including the galactic foreground and the radio antenna beam, as well as methods for robustly constraining and removing them from radio spectrometer data aimed at detecting the 21-cm signal. We also present an analysis describing how warm dark matter and population III stars affect the shape of the sky-averaged 21-cm signal and an analysis of their detectability in the presence of degeneracies with other astrophysical model parameters and systematic noise. Lastly, we present new results from the first radio telescope of NASA’s to land on the Moon, ROLSES-1, including potential techno-signatures detected from the Earth and constraints upon the isotropic galactic background spectrum, both the first measurements of their kind from the surface of the Moon. We present the methods for calibrating, cleaning, and reducing the raw data, as well as the statistical methods used to extract antenna parameter values and the amplitude of the galactic spectrum. Lastly, we outline some methods for use in modeling and 21-cm signal extraction in the future, and how our methods may be applied to upcoming lunar radio telescopes.</p
Engineering Stimuli-Responsive Optical Elements: Synthesis, Processing, and Optical Characterization of Liquid Crystalline Elastomers
Full text linkThis thesis broadly focuses on engineering the molecular composition, optical properties, and associated stimuli-response of liquid crystalline elastomers (LCEs) that retain the chiral nematic (cholesteric) phase (CLCEs). The optical properties of the CLCEs are reconfigured through the application of thermal, mechanical, and electrical stimuli. CLCEs are intrinsically solid and flexible elements. Accordingly, CLCEs can be envisaged in distinctive integrations and form factors in applications in sensing, lasing, and the built environment. Motivated by the prospective functional utility and implementation of CLCEs, this thesis explores the intercoupling of composition, mechanical properties, and stimuli-response in these materials. The themes of this thesis will be expressed with functional focus. Fundamental contributions are noted and drawn out where appropriate.
Numerous prior examinations detail thermochromism in CLCEs. Thermochromism is intrinsically a slow process, and the magnitude of reflection wavelength change is limited. Accordingly, we first explored the realization of electromechanical reconfiguration of CLCEs as an electrochromic media. Our approach was to insert CLCE as the active dielectric layer in a dielectric elastomer actuator (DEA) geometry. Transparent compliant electrodes were coated onto both sides of the CLCE. Upon application of an electric field, electrostatic forces compressed the CLCE to result in a blue shift in the selective reflection. A mechanical pre-bias was shown to enhance the electro-optical tuning due to the reduction in modulus.
Next, motivated by emerging applications (e.g., LiDAR, AR/VR, and beam steering) in infrared optics, we prepared long pitch CLCEs with reflection in the short-wave infrared (SWIR) and mid-wave infrared (MWIR). The preparation of infrared-reflecting CLCEs has surprisingly not been pursued. Materials compositions and processing approaches were developed to retain well-aligned CLC phase in appropriately thick CLCEs. Importantly, alignment utilized both surface and electric field enforced alignment techniques. As an unexplored optical media, first I explored the optomechanical response of SWIR- and MWIR-reflecting CLCEs to direct (e.g., tensile) or indirect (e.g., DEA) deformation. This functionally motivated examination revealed a surprising result: the optomechanical response of long pitch CLCEs is pitch dependent. Examination of mechanical properties of CLCEs indicates that this deviation may be associated with the pitch dependence of the compressive modulus.
The pitch-dependent findings inspired additional exploration of the optomechanical response of CLCEs to mechanical strain. Specifically, I hypothesized that depolarization of CLCE reflection to deformation is dependent on the number of helical rotations (Np) and pitch length. To elucidate this hypothesis, I undertook an extensive structure-response examination to ascertain the association of pitch length, Np, and mechanical properties on the optomechanical response of CLCEs. Distinctive characterization of deformed CLCEs confirmed that low Np CLCEs shear in the direction of strain resulting in loss of Bragg reflection before enhancement of the reflection notch can be observed.
These examinations utilized acrylate-based reactions to prepare CLCEs. To enable greater tunability in mechanical properties as well as realize more homogeneous polymers, this thesis concludes by detailing the preparation of LCEs via thiol-ene photopolymerization. Thiol-ene photopolymerization proceeds by a step growth mechanism. The sequential nature of the thiol-ene reaction forms homogeneous polymer networks largely before gelation (which can occur as late as 70% conversion in some formulations examined here). I detail a two-pronged examination of thiol-ene LCE preparation. First, I jointly undertook a systematic study of the preparation of thiol-ene LCEs subject to surface-enforced alignment to ascertain the effects of phase, alignment, and crosslinking density on material properties and stimuli-response. Second, I utilized these insights to prepare surface aligned CLCEs by thiol-ene photopolymerization. I found that CLCEs prepared by thiol-ene photopolymerization had improved optical quality (i.e. low haze). The modulus of the CLCE was tunable by controlling the concentration of crosslinker to chain extender in the formulation.</p
Subgrid Models for Electron-Scale Tokamak Turbulence
Full text linkTokamaks are currently the leading concept for thermonuclear fusion reactors, using magnetic fields to toroidally confine a hot plasma and achieve the conditions necessary for sustained fusion. However, experiments reveal anomalous heat and particle losses which far exceed collisional transport predictions and significantly degrade confinement. The anomalous radial transport is now known to result from drift-wave microturbulence, driven unstable in the plasma by the intense pressure gradients involved. Understanding these turbulent transport mechanisms is critical for predicting and maintaining steady-state energy production. After extensive development efforts, gyrokinetic theory and numerical modeling have emerged as essential tools for studying the complex nonlinear dynamics of tokamak microturbulence.
Gyrokinetic simulations at ion gyroradius scales have successfully reproduced transport char�acteristics in agreement with experiment, but often underestimate electron thermal transport levels. The electron-temperature-gradient (ETG) mode, arising at electron gyroradius scales, is a key candidate to explain excess electron heat losses. ETG transport is expected to be particularly important in reactor-relevant plasmas like ITER, where ETG turbulence can interact with ion-scale turbulence through complex multiscale processes which are sensitive to small variations in equilibrium parameters. Direct simulation of these interactions remains computationally prohibitive, even on exascale computing platforms, thereby motivating the development of the subgrid model presented here. The subgrid model captures electron-scale effects in a reduced form suitable for whole-device modeling of future burning plasmas.
Quasilinear modeling offers an efficient method for predicting turbulent transport spectra by leveraging linear gyrokinetic simulation results. Quaslinear theory is introduced here for modeling ion-scale turbulence in DIII-D shot #162940 using linear gyrokinetic simulation. The quasilinear predictions show good agreement with nonlinear flux spectra, and analysis is successfully extended to negative triangularity shaping - a plasma configuration which has reported reduced turbulent transport levels. Quasilinear models are further compared against nonlinear gyrokinetic ETG simulations and considered for reduced modeling of local electron-scale turbulence effects in global ion-scale simulation.
A key mechanism of instability regulation is by perpendicular shearing from zonal flows (ZFs), which break up radially-elongated drift wave eddies. These are self-generated shear flows which are driven by growing primary instabilities as nonlinear effects become significant. Intermediate-scale gyrokinetic theory, encompassing wavelengths much shorter than the ion gyroradius but much longer than the electron gyroradius, predicts strong ETG-ZF coupling which is expected to drive significant ZF generation and ETG mode regulation. Zonal flow generation due to a single ETG mode is investigated in local single-mode gyrokinetic simulations and intermediate-scale results are found to be in agreement with the gyrokinetic theory. Full-spectrum results are then presented and explained qualitatively in terms of the single-mode results. The resulting intermediate-scale zonal flows have been reported to help regulate ion-scale turbulence levels in multiscale gyrokinetic simulation.
A subgrid ETG model is then demonstrated which averages local electron-scale turbulence over intermediate scales in space and time to include in global ion-temperature-gradient (ITG) simulations. This approach results in ion-scale equations which incorporate the electron heat transport from ETG turbulence and effects of electron-scale turbulence on the ion scale. Local ETG simulations are performed at different radial locations and a kinetic form of the flux is added to global ion-scale simulations as a source term. Analytic radial profiles of ETG heat flux are constructed and compared to flux-tube results at multiple radial locations. Different ratios of ITG to ETG heat flux levels are considered and the results of capturing ETG heat transport in global ion-scale simulations are discussed. Potential coupling of the ETG streamer potential and intermediate-scale zonal flows to the ion scale is further addressed. </p
Separated by Space: Insights Into Social Bonds in Spaceflight From Prairie Vole Models
Full text linkLong-duration space missions introduce unique psychological challenges, particularly with respect to social isolation and its potential impact on human social bonds. This study used prairie voles as an animal model to explore the effects of prolonged separation on social behavior in prairie voles, with a focus on partner directed behaviors. While there are challenges in translating human-like social behaviors to animal models, prairie voles offer a valuable model due to their natural pairbonding tendencies. One group experienced intermittent exposure to their partner to simulate potential communication opportunities during long-duration spaceflight, while the other group remained fully isolated. Both groups underwent a partner preference test before and after separation to assess the effects on social bonding. Partner preference scores were assessed before and after a six-week separation period. The mean partner preference score for the reunited group was post separation was 0.82 ± 0.10, and for the separated group, it was 0.62 ± 0.31. Results showed no statistically significant difference observed between the treatment and control groups (p > 0.05 for both timepoints); however, the separated group showed higher variability in partner preference, with some animals displaying a greater preference for novel partners after the separation period. This variability suggests that, with separation periods longer than six weeks, partner preference may undergo shifts. Factors contributing to the lack of statistical significance include a limited sample size and high inter-individual variability. These preliminary findings highlight the complexity of studying social bonding under prolonged isolation, suggesting avenues for future research with larger samples and extended separation times. Such insights could be valuable for developing countermeasures to support astronaut mental health and social resilience as space missions grow in duration and distance from Earth.</p
The Role of Cellular Senescence and the Senescence-Associated Secretory Phenotype in Vascular Aging: Amelioration by the Natural Senolytic Fisetin
Full text linkCardiovascular diseases (CVDs) remain the leading cause of death globally, with advancing age being the primary risk factor for CVD development. Age-related vascular dysfunction, characterized by the stiffening of the large elastic arteries and vascular endothelial dysfunction, represents the primary antecedent to the development of CVDs. As such, understanding the mechanisms that drive age-related vascular dysfunction and establishing effective interventions to improve arterial health are biomedical research priorities. Cellular senescence, a multifactorial stress response, accumulates with advancing age and promotes vascular dysfunction through the production of the senescence-associated secretory phenotype (SASP) which drives chronic inflammation and excess oxidative stress. Senolytics, compounds that selectively eliminate senescent cells, hold promise in reducing excess cellular senescence and the SASP and subsequently improving or preventing age-related vascular dysfunction.
The purpose of this dissertation research was to identify promising senolytic interventions to suppress excess cellular senescence and the SASP and enhance vascular function with aging. In a review of the literature, I compiled the putative and established mechanisms by which vascular senescent cells and the SASP may contribute to vascular aging. I collected evidence of the effects of senolytic therapies on vascular health and identified groups that had high cellular senescence and SASP burden and impaired vascular function that might stand to benefit the most from senolytic treatment. In a preclinical intervention study, I found that latelife supplementation with the natural senolytic fisetin enhanced endothelial function and lowered arterial stiffness in old mice. These improvements were mediated by a suppression of excess vascular cell senescence and associated with reduced oxidative stress and favorable remodeling of the arterial wall. In a mechanistic study, I identified aortic endothelial cells to be highly susceptible to becoming senescent in the context of aging and are readily eliminated by fisetin supplementation. Further, I demonstrated that the SASP was an underlying mechanism of agerelated endothelial dysfunction and identified chemokine 12 (CXCL12) as a SASP factor that mediated endothelial dysfunction with aging that could be modulated with senolytic intervention.
Collectively, these studies establish cellular senescence and the SASP as causal contributors to the age-related decline in vascular function and demonstrate that senolytic interventions have efficacy in improving or preventing vascular function with aging. Thus, these findings open new avenues for the development of preventative and therapeutic interventions targeting cellular senescence and the SASP to improve cardiovascular health in aging populations. </p
NEPC Review: ESA’s in Arizona: Q3 2025 Report (Common Sense Institute Arizona, October 2025)
Full text linkA recent report examines two key questions about Arizona’s ESA program: how much it will cost in the coming year and the characteristics of ESA users by household income and race/ethnicity. The report concludes that the program is now “essentially fully subscribed,” suggesting it will not see the runaway growth in students or state costs experienced in the past two years, and that current ESA costs are largely offset by declining public-school enrollment. Given limited data on the program’s volatility, however, policymakers should not assume the major financial hits are behind them.</p
Oceania Newspaper Coverage of Climate Change or Global Warming, 2000-2025 - August 2025
No full textThe Media and Climate Change Observatory Data monitors 131 sources (across newspapers, radio and TV) in 59 countries in seven different regions around the world. Data is assembled by accessing archives through the Lexis Nexis, Proquest and Factiva databases via the University of Colorado libraries. More information may be found at: http://mecco.colorado.edu.</p
World Radio Coverage of Climate Change or Global Warming, 2000-2025 - November 2025
No full textThe Media and Climate Change Observatory Data monitors 131 sources (across newspapers, radio and TV) in 59 countries in seven different regions around the world. Data is assembled by accessing archives through the Lexis Nexis, Proquest and Factiva databases via the University of Colorado libraries. More information may be found at: http://mecco.colorado.edu.</p
NEPC Review: Wisconsin’s Most Cost-Effective K-12 Program (School Choice Wisconsin, August 2025)
Full text linkWisconsin’s long-running private school voucher program has drawn decades of research interest, including a recent report from School Choice Wisconsin. The report claims voucher-receiving schools in Racine, Milwaukee, and statewide are far more cost-effective than public district schools. But its analysis is not just flawed—it’s wrong. Cost-effectiveness ratios are inappropriate for comparing schools serving different student populations, and further errors in spending, outcome, and demographic data compound the problem. In short, School Choice Wisconsin conducted the wrong analysis in the wrong way, making the report useless for policymaking.</p
African Newspaper Coverage of Climate Change or Global Warming, 2004-2024 - December 2024
No full textThe Media and Climate Change Observatory Data monitors 131 sources (across newspapers, radio and TV) in 59 countries in seven different regions around the world. Data is assembled by accessing archives through the Lexis Nexis, Proquest and Factiva databases via the University of Colorado libraries. More information may be found at: http://mecco.colorado.edu.</p
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