This dissertation reports on new material developments as detailed in three chapters discussing the development of high Verdet constant materials containing magnetic nanoparticles (NPs) and one chapter discussing sulfur-containing polymers for infrared (IR) optics applications. The first three chapters will cover the synthesis and characterization of different types of magnetic nanoparticles followed by their incorporation into polymer systems to generate composite materials. Further, the processing techniques utilized to generate magneto-optic (MO) devices from these composites will be discuss as well as their performance related to both the processing methodology used and the properties of the nanoparticles. For chapters 2 and 3, additional experimental information and supporting data can be found in the corresponding appendix chapters. The fourth chapter will cover recent work analyzing the transparency of polymer materials in the IR.The first chapter is the first comprehensive review summarizing the field of high Verdet constant MO materials. The Faraday effect is a type of MO phenomenon where the polarization direction of linearly polarized light is rotated when passing through transparent media under the application of a magnetic field along the direction of the light propagation. At a certain wavelength and temperature, the angle of rotation is directly proportional to the strength of the magnetic field, the path length of the medium, and the Verdet constant of the material. For MO devices, maximizing the rotation angle of the light is desired for device miniaturization and fabrication cost and can be accomplished by increasing any of the aforementioned parameters, but for devices with size constraints and with the limitations of sustainable magnetic fields, high Verdet constant materials are desired. The development of high Verdet constant materials has been ongoing since the discovery of the Faraday effect in the mid-1800s and has come to encompass a variety of material classes from hard matter glasses, crystals, and ceramics, to soft matter small molecules and synthetic polymers, and some composite materials containing both hard and soft matter. The most widely used materials for MO applications have traditionally been glasses and crystals with Verdet constants on the order of 103-104 °/T·m at room temperature when measured in the visible to near-IR range. However, more recent work has shown promising soft matter systems composed of small molecules, polymers, and nanoparticle-polymer nanocomposites with enhanced Verdet constants ranging from 104-106 °/T·m. Chapter 1 is designed to give a broad overview of the different types of high Verdet constant materials with an emphasis on the recent development ultra-high Verdet constant materials such as conjugated polymers and nanoparticle-polymer composites. The second chapter will discuss the preparation of polymer-nanoparticle composite Faraday rotators. As mentioned previously, most applications of Faraday rotators use a variety of hard matter materials to accomplish MO rotation. These materials are however limited by low Verdet constants (when compared to many soft matter systems) which has led to an increased interest in soft matter both for increased Verdet constants and for enhanced processing capabilities. The new type of MO material discussed is based on MO active cobalt ferrite (CoFe2O4) nanoparticles combined with poly(styrene) (PS) to form solution-processable composites. This study examines the importance of exchanging the surface ligands on the CoFe2O4 nanocrystals to polymer ligands that are more compatible with the PS phase of the composite. With surface compatible ligands, the NPs could be dispersed in a polymer matrix at variable loadings from 2.5-15 wt%. The solution processing techniques employed for this system allowed the MO response to be tuned by simply varying the NP loading and the number of layers in the composite. The Faraday rotators were prepared by a multilayer polymer film construct wherein alternating layers of the NP-polymer composite and cellulose acetate were spin coated allowing for an increased path length of the MO active NP-polymer layers with protective layers of cellulose acetate. These multilayered Faraday rotators demonstrated a nearly 10X increase in Verdet constant compared to a terbium gallium garnet reference material at 1310 nm and demonstrated the importance of exploring soft MO materials for enhanced MO responsive materials. The third chapter will discuss an expansion on the previous work with CoFe2O4-polymer composites. The previous work established a construct for how Faraday rotators could be produced by solution-processing using alternating layers of MO active materials to achieve a strong MO response. In this work polymer coated cobalt (Co) nanoparticles were used and offered several advantages over the previously used CoFe2O4 NPs. The synthetic strategy employed to produced Co NPs uses a native polystyrene ligand which eliminated the ligand exchange processing step and provided enhanced dispersion in the polystyrene matrix. This enhanced dispersion allowed for NP loadings up to an astonishing 50 wt% with the same tunability as the previous system. In addition to solution processing, the enhanced dispersion allowed for the formation of composites that could be melt-processed into free standing films with significantly increased thicknesses. The synthetic strategies employed additionally allowed for the synthesis of a range of particle sizes from 9 to 17 nm. This allowed, for the first time, a systematic study Verdet constant with the size dependent magnetic properties of the NPs. Due to both the increased NP loading and a stronger magnetic moment from Co NPs compared to CoFe2O4 NPs the measured Verdet constants were 2-3 orders of magnitude higher than our reference terbium gallium garnet material or our previous NP-polymer composites. The fourth chapter will cover recent work on IR imaging and the importance of uniform reporting techniques for IR transparency. There have been recent reports of new IR transparent polymers that only report the IR transparency measurement as thin films. This chapter demonstrated that thin films of poly(methyl methacrylate) PMMA (a demonstrably poorly IR transmissive polymer) could mistakenly be described as an IR transparent, transmissive optical polymer. To definitively illustrate the non-uniformity of polymer films and windows reported for IR optics, PMMA windows of progressively increasing thickness were prepared for FTIR measurements to quantity optical transmittance in the IR spectrum, along with MWIR imaging experiments. These results were then compared to poly(sulfur-random-diisopropenylbenzene) (poly(S-r-DIB)), our previously established MWIR transparent polymer. The report provided both qualitative and quantitative analysis of PMMA and p(S-r-DIB) and how only reporting on thin film properties of polymers can lead to misrepresentation of the polymer’s IR transparency. These results set a standard for how IR transparency in polymers should be reported.

Background: Evolving research in the psychiatric literature has suggested that the auditory cortex region is smaller in people with schizophrenia who experience auditory hallucinations than in normal control individuals. These findings are not without controversy. While there has been significant research considering volumetric variance in pathologic brains with AH, there is a paucity of data considering the influence of morphology and surface area of primary auditory structures. Purpose: The purpose of this set of studies was to evaluate and compare the following variables in schizophrenic and control brains, both between groups and between hemispheres within groups: surface area of Heschl’s gyrus (HG) and planum temporale (PT), length of the Sylvian fissure (SF), length of the posterior extending ramus of the SF, and the morphological variants of HG, PT, and the posterior ramus. Evidence of morphologic variance or surface area differences in populations that are prone to experiencing auditory hallucinations may provide new or additional insight into the role of these neuroanatomical structures in central auditory processing during auditory hallucinations. Hypothesis: Based on the previous literature we had several hypotheses: (1) in separate structure analyses with regards to surface area, there will be reduced asymmetry for primary auditory structures (HG & PT) in schizophrenic brains with hallucinations compared to controls; (2) there will be reduced typical asymmetry in Sylvian fissure (SF) length for schizophrenic brains with hallucinations compared to controls; and (3) there will be consistent patterns of morphologic differences in at least one category of Heschl’s gyrus, planum temporale, or posterior ramus variants between schizophrenic brains with hallucinations and control brains. Methods: Imaging analysis was conducted using BrainVISA Anatomist software and MRIcron software to assess 51 control brains (102 hemispheres) from the Open Access Series of Imaging Studies (OASIS) repository and 51 schizophrenic brains (102 hemispheres) obtained from the NUSDAST (Northwestern University Schizophrenia Data and Software Tools) database. These neuroimaging softwares were used to quantify surface area of HG and PT, morphology of HG and PT, length of SF, and angle of the posterior extending ramus of SF. Results: This study found a lack of typical asymmetry between right and left HG in schizophrenic brains, and a significantly larger HG in the right hemisphere of controls compared to schizophrenics. There was also reduced asymmetry of the SF length in schizophrenics compared to controls. No significant findings were established for either PT surface area or morphological classifications of HG, PT, or posterior ramus. Key Words: Auditory Hallucinations, auditory cortex, anatomy, Heschl’s gyrus, planum temporale, superior temporal gyrus, Sylvian fissure, posterior ramus, ascending ramus, schizophrenia Abbreviations: Auditory Hallucinations (AH), central auditory nervous system (CANS), Heschl’s gyrus (HG), planum temporale (PT), planum polare (PP), primary auditory cortex (A1), Sylvian fissure (SF), schizophrenia (SZ), superior temporal plane (STP), supramarginal gyrus (SMG), region of interest (ROI)

Imaging is the process of reproduction of an object’s form. Image science is a multidisciplinary field concerned with the generation, collection, duplication, analysis, modification, and visualization of images.Traditionally, the image of an object is generated by gathering optical power reflected or absorbed by the object directly with a detector array in a one-to-one manner. For example, in optical photography, reflected or emitted photons from object are directly captured by optical elements (e.g. lens, mirror) and focused onto a detector array. However, in many scenarios where such direct imaging is not feasible, one is forced to gather information that is only indirectly related to the object. In some extreme cases, we are forced to work with only scattered photons from the object of interest. In this work, we explore two of these special cases and propose two novel indirect imaging (scattering-based) approaches operating at different wavelengths. The first indirect imaging approach we consider a novel non-line-of-sight (NLOS) imaging technique. Non-line-of-sight imaging refers to the imaging of an object that is not directly visible from the viewer/imaging perspective. A classic NLOS setup usually involves emission and collection of photons actively with time-of-flight measurements. To accurately measure a photon’s traveling time, most approaches employ expensive and exotic optical sources and detectors such as ultrafast laser and ultra high-resolution single photon avalanche detector (SPAD). In this work, we instead propose a novel passive NLOS imaging method that works with ambient light illumination and employs only commonly available imaging elements. We develop a light path order based image formation model, a learning-based model parameter estimation process, and successfully demonstrate instant passive NLOS imaging. We discussed the limitation of this technique and possible applications We then shift our focus to ultra-short wavelength or higher photon energy. In this part, we study a different type of imaging referred to as X-ray diffraction tomography (XRDT). X-ray diffraction tomography is a tomographic imaging of the coherent scattering profile (X-ray form factor) of an object and its material. Coherent scattering is one of three forms of photon interactions possible in the X-ray photon energy ranging from 10 kev to 200 kev. It occurs when X-ray photon energy is relatively small compared to the ionization energy of the atom. When a coherent scattering event happens, the photon does not have enough energy to liberate the electron from its bound state and no energy transfer occurs. Instead, the X-ray photon gains momentum from the micro-structure of the material and undergoes a change in its direction (scatter). Therefore, the scatter direction contains vital information of the micro-structure of the material and is unique to different materials. The scattering pattern is called momentum transfer function or X-ray form factor. It is considered as the golden standard in material classification. In this work, we explore the inherent sparsity in the X-ray form factors and develop a sparsity regularized reconstruction algorithm to perform maximum-a-posteriori estimation for X-ray diffraction tomography. We demonstrate the possibility of achieving higher energy resolution with limited number of photon, which allows our system to run on a lower signal-to-noise ratio.

Considering that the southwestern United States provides many of the specialty crops to feed the entire nation, it is vital to maximize use of water and fertilizer in croplands in this region. Meanwhile, intensifying droughts exacerbate cropland dependence on irrigation water. Therefore, solutions are needed to maintain cropland productivity. Adding carbon-rich organic amendments temporarily improves soil properties by increasing water and nutrient retention, but benefits are short-lived as organic amendments degrade quickly in hot, arid climates. Biochar is an organic amendment that can potentially improve long-term cropland soil health, which is the ability of soil to store and provide water and nutrients for plant growth. Biochar provides a relatively stable carbon source and can increase water and nutrient retention. Most studies on the effectiveness of biochar for these purposes have been conducted in temperate agroecosystems, but few studies examine effects of biochar on soil properties in croplands of the desert southwest U.S. Therefore, the purpose of this research is to deepen understanding of effects of carbon inputs (i.e. biochar and compost) to retain more water and provide plant-available nutrients in an irrigated desert cropland.

Over forty years ago, women across Lima, Perú’s poorest neighborhoods decided to take their community’s need for food into their own hands. Amidst an economic downturn that swept across Latin America in the last decades of the 20th century, these volunteers, the socias, formed comedores populares (communal kitchens). The socias combined their resources to cook for their families, while selling meals at an affordable price to their neighbors, investing all profit in the next day’s meal. In the early 1980s, the Peruvian government began opening state-sponsored comedores, providing participating kitchens with food aid. As state-sponsored comedores have evolved over the past four decades, they have become sites of contested meaning and significance amidst a confluence of embedded structural inequalities, conflicting sociopolitical subjectivities, and a politics of false generosity. While the state has long used the comedores for political ends, a practice which remains entrenched in today’s Peruvian political practices, outside observers have blamed comedores for reproducing irresponsibility, underdevelopment, malnutrition, political corruption, and the perpetuation of systemic injustices. These overlapping complexities have created a context in which comedores are facing increasing pressure to close, forcing socias to fight to keep their kitchens open. Drawing on ethnographic research with state-sponsored comedores in Huaycán, Lima, Perú, colloquially known as ‘The City of Hope,’ this research explores the relationship between the inside meaning of comedores for participating socias and the external challenges socias confront as they struggle to continue cooking together. While food aid programs such as the comedores are unlikely to upend Perú’s underlying structural challenges, for many socias, the comedores are a vital resource for ameliorating the hardships of chronic economic precarity, while also providing a valuable space of social solidarity and camaraderie. In examining these dynamics, this research addresses broader debates around food aid distribution, the violence of precarity, and the value of communal spaces within a neoliberal socioeconomic context. Additionally, in turning to the experiences of comedor socias in Huaycán, this dissertation considers how deep-seated injustices in poor communities have produced predictable and preventable suffering and death due to COVID-19.

Good Thinking is a collection of papers about abilities, skills, and know-how and the distinctive but often overlooked—or explained away—role that these phenomena play in various foundational issues in epistemology and action theory. Each chapter, taken on its own, represents a fairly specific intervention into debates in (i) epistemic responsibility, (ii) the nature of inferential justification, and (iii) connections between inference and action. But taken collectively, these chapters constitute fragments of a larger mosaic of commitments about the explanatory priority of abilities in normative theories. One distinctive argumentative strategy employed throughout Good Thinking is its placing special emphasis on what might be called “bad thinking”: defective judgments borne out of cognitive short-circuiting, incoherence or self-doubt, depression, or anxiety. The underlying motivation for this is that much of what we can learn about good thinking is only revealed at the margins, where thinking has in some respects gone bad without being entirely spoiled.

Optical Whispering gallery mode (WGM) microresonators, which benefit from an ultra-high quality (Q) factor and small mode volume to significantly enhance light-matter interaction, stand out from other sensors, and are utilized in a variety of biochemical sensing or physical parameter detection applications. Physical or chemical reactions occurring in the evanescent field of the polymer-treated microtoroid equatorial plane will be translated into variations of the WGM spectra, which will, in turn, be recorded and analyzed through techniques such as frequency locking, balanced detection, and post data processing. The overall platform is known as the Frequency-locked optical whispering evanescent resonator (FLOWER) system. The performance and characteristics of ultra-sensitive and selective WGM gas sensors are evaluated and demonstrated in this dissertation. Two approaches to further improve the system are proposed, one based on plasmonic near-field enhancement to improve the sensitivity and the other on a fiber metrology method using Rayleigh backscattering to eliminate the thermal noise of the sensing system. Finally, another sensing application using the dual-FLOWER system for particle shape analysis is introduced.

A more complete understanding of the global distribution of cirrus ice clouds is essential to constraining both long and short-term climate forecasts. Radiometric simulations have shown that joint polarimetric measurements in the sub-mm and long-wave-infrared (LWIR) can significantly increase sensitivity to ice-particle microphysics, however, no existing platforms have polarimetric sensitivity in LWIR. This work describes the design and demonstration of an InfraRed Channeled Spectro-Polarimeter (IRCSP) to address this gap in existing remote sensing technology. The IRCSP utilizes commercially available uncooled microbolometer detectors (UMBs), is less than 10 cm long, has no moving mechanical components, and requires no active thermal control. A robust data-reduction algorithm corrects for both focal plane temperature fluctuations and instrumental polarization error to measure both the AoLP and Degree of Linear Polarization (DoLP) of cold targets. Lab validation studies have demonstrated polarimetric sensitivity to targets with 1.0% DoLP and brightness temperatures of less than 270 K. In 2021, the IRCSP was demonstrated in the near-space environment as a piggyback out of NASA Columbia Scientific Ballooning Facility. Post landing the instrument was retrieved with no damage to the optical payload and collected over 150 minutes of flight data at altitudes above 30 km. These measurements demonstrate the operation of un-cooled microbolometers in the low-pressure environment and are the first known high-altitude observations of a polarized signal from cloud tops in the LWIR. During deployment, the IRCSP reported brightness temperatures between 250-285K with uncertainty of < 1.5K. In addition, the IRCSP detected statistically significant polarization modulation with DoLP between 1 − 20% and preferential AoLP trends. These results support the hypothesis that LWIR polarimetry has the potential to add new sensitivity to existing remote sensing platforms.

Gamma-ray detectors operating under the tracer principle have been widely used in medical imaging for decades. One such application is single-photon computed tomography (SPECT), which reconstructs 3-dimensional images of radiotracer concentration in vivo, revealing regions of biological function inside a body. For most of SPECT's history, the dominant technology used to sense gamma energy deposition events was that of photomultiplier tubes (PMTs). A majority of gamma cameras used in SPECT applications employ an array of PMTs to isolate the location of gamma-ray interaction inside the camera; the collection of PMT signals provides essential information to determine the origin of the gamma-ray emission and reconstruct an image. Recent advances in solid-state detectors have introduced a viable alternative to PMTs as a means to detect signals with single-photon sensitivity: the silicon photomultiplier (SiPM). SiPMs have numerous attractive properties that make them well suited to the tasks required for gamma cameras; namely, fine pixelation, low profile, and high gain. Augmenting an array of PMTs in a gamma camera with SiPMs can produce higher resolution images, enabling radiologists and drug researchers to conduct studies with higher accuracy and lower probability of error. Another major development of the 21st century was the advent of 3-dimensional additive manufacturing techniques using metal. A 3-D tungsten printer enables entirely new geometries to fabricate, including pinhole apertures used as SPECT image forming devices. Moreover, the custom printed pinholes are easily made into formats having adjustable diameters to fine-tune imaging properties in a SPECT session. This, coupled with the new SiPM arrays, forms the foundation of the new technology brought to bear in AdaptiSPECT-C, a stationary clinical whole-brain SPECT imager. AdaptiSPECT-C will be used in drug discovery research targeting neurodegenerative diseases such as Parkinson's and Alzheimer's. The novel incorporation of hybrid PMT / SiPM cameras and dynamically adaptable apertures will produce images at higher resolution and with higher fidelity pharmacokinetic information than rival systems, positioning it as a leading technology in drug development for neurodegenerative disease. This dissertation covers the development of AdaptiSPECT-C hardware, addressing the early performance simulations, the mechanical design of its cameras and gantry structure, and the electrical design of its front-end electronics, with results from prototype unit testing. Ultimately, by demonstrating functional prototype cameras, the work in this dissertation establishes a strong proof-of-concept for AdaptiSPECT-C as a system, and offers a roadmap for its imminent completion.

The first two chapters investigates the issues that arose after individuals experienced certain shocks that affected their health. Chapter 1 focuses on the short-run and long-run effect of childhood maltreatment on mental health. Chapter 2 investigates the effect of a new medication, PrEP, on individuals’ risky sexual behaviors and sexually transmitted infections. The last chapter exams the relationship between individuals’ timing pattern of working and their success in the setting of online game streaming. Time Heals All Wound? Childhood Maltreatment and Mental Health Empirical evidence has shown that maltreatment may cause serious damage to the human capital development of children and result in negative outcomes in their adulthood. Mental health may be one of the underlying mechanisms through which maltreatment affects human capital accumulation. Using the data from the Longitudinal Study of Adolescent to Adult Health, I examined the relationship between childhood maltreatment and mental health both in the short run and in the long run. The results show the childhood experience of maltreatment imposes negative effect on mental health. The effect is at least significant in the long run, suggesting that the effect is long-lasting and does not necessarily fade away as time passes. Females are on average more vulnerable to maltreatment than males. Experiencing multiple forms of maltreatment would impose a worse effect on mental health compared to single form of maltreatment. PrEP, Risky Sexual Behaviors and STIs Pre-exposure prophylaxis, or PrEP, is a daily medicine for people at high risk of contracting HIV to lower their chance of getting infected. Clinical studies show that PrEP can be highly effective, reducing the risk of contracting HIV by more than 90\%. Despite the great effectiveness of PrEP in preventing HIV infection, there is concern that PrEP may lead some people to more risky behaviors, such as reducing their use of condoms and increasing their number of sexual partners. Using public data from the Multicenter AIDS Cohort Study, this paper empirically examines such concern. Exploiting the panel nature of the data, we use a difference-in-difference model to study the effect of PrEP on risky sexual behaviors and other sexually transmitted infections (STIs). Our analysis shows that PrEP makes individuals more likely to engage in unprotected anal sex, have more sexual partners, and more likely to contract syphilis. The Early Bird Gets the Worm: Strategic timing to live-stream on Huya.com Using scraped data from an online video game live streaming platform, I study the streamers' strategic decisions of when to go online and the effects of these timing pattern on their success on the platform. Live streamers as the content creators face different amount of audience during different times of the day as the website traffic fluctuates over the course of 24 hours. They also face different levels of competition as the number of online streamers change in each hour. I use a simple model of streamers' behaviors as benchmark of market equilibrium and study how the real data deviate from the model predictions. The result show live streamers exhibit over competition and decreased gains in rush hour and in contrast they also present under competition and increased gains in the slow hour. Potential rationales are discussed to explain such phenomenon.