Now showing items 1-20 of 16728

    • T-cell cellular stress and reticulocyte signatures, but not loss of naïve T lymphocytes, characterize severe COVID-19 in older adults

      Jergović, Mladen; Watanabe, Makiko; Bhat, Ruchika; Coplen, Christopher P; Sonar, Sandip A; Wong, Rachel; Castaneda, Yvonne; Davidson, Lisa; Kala, Mrinalini; Wilson, Rachel C; et al. (Springer Science and Business Media Deutschland GmbH, 2023-01-12)
      In children and younger adults up to 39 years of age, SARS-CoV-2 usually elicits mild symptoms that resemble the common cold. Disease severity increases with age starting at 30 and reaches astounding mortality rates that are ~330 fold higher in persons above 85 years of age compared to those 18–39 years old. To understand age-specific immune pathobiology of COVID-19, we have analyzed soluble mediators, cellular phenotypes, and transcriptome from over 80 COVID-19 patients of varying ages and disease severity, carefully controlling for age as a variable. We found that reticulocyte numbers and peripheral blood transcriptional signatures robustly correlated with disease severity. By contrast, decreased numbers and proportion of naïve T-cells, reported previously as a COVID-19 severity risk factor, were found to be general features of aging and not of COVID-19 severity, as they readily occurred in older participants experiencing only mild or no disease at all. Single-cell transcriptional signatures across age and severity groups showed that severe but not moderate/mild COVID-19 causes cell stress response in different T-cell populations, and some of that stress was unique to old severe participants, suggesting that in severe disease of older adults, these defenders of the organism may be disabled from performing immune protection. These findings shed new light on interactions between age and disease severity in COVID-19.
    • Non-reciprocal acoustoelectric microwave amplifiers with net gain and low noise in continuous operation

      Hackett, Lisa; Miller, Michael; Weatherred, Scott; Arterburn, Shawn; Storey, Matthew J.; Peake, Greg; Dominguez, Daniel; Finnegan, Patrick S.; Friedmann, Thomas A.; Eichenfield, Matt; et al. (Springer Science and Business Media LLC, 2023-01-16)
      Piezoelectric acoustic devices that are integrated with semiconductors can leverage the acoustoelectric effect, allowing functionalities such as gain and isolation to be achieved in the acoustic domain. This could lead to performance improvements and miniaturization of radio-frequency electronic systems. However, acoustoelectric amplifiers that offer a large acoustic gain with low power consumption and noise figure at microwave frequencies in continuous operation have not yet been developed. Here we report non-reciprocal acoustoelectric amplifiers that are based on a three-layer heterostructure consisting of an indium gallium arsenide (In0.53Ga0.47As) semiconducting film, a lithium niobate (LiNbO3) piezoelectric film, and a silicon substrate. The heterostructure can continuously generate 28.0 dB of acoustic gain (4.0 dB net radio-frequency gain) for 1 GHz phonons with an acoustic noise figure of 2.8 dB, while dissipating 40.5 mW of d.c. power. We also create a device with an acoustic gain of 37.0 dB (11.3 dB net gain) at 1 GHz with 19.6 mW of d.c. power dissipation and a non-reciprocal transmission of over 55 dB.
    • Student Feedback Regarding Online Course Production Value: A Case Study from Classics

      Stephan, Robert P.; University of Arizona, Department of Religious Studies and Classics (IEEE, 2022-09)
      This paper employs a data-driven approach to understanding the relationship between online course production quality, instructional effectiveness, and student satisfaction. To accomplish this, it assesses data from six years of student evaluations for online courses and compares it to the production style and quality present in those courses. The quantitative multiple choice course evaluation questions speak to issues of overall quality and satisfaction, student learning, and content and lesson clarity. Qualitative student comments are also assessed to understand the degree to which production quality is highlighted as a driving factor in both student enjoyment and instructional effectiveness. Finally, trends in evaluation data are analyzed in conjunction with the quality and style of each course to provide a better understanding of how students perceive the value of production quality. This project serves as an important step in furthering evidence-based online pedagogy and provides valuable insights for how to best allocate time and resources with regard to online course production.
    • The Cost of High Production Quality: A Preliminary Discussion of the Value of Production in Asynchronous Online Modalities

      Simmons, Caleb; University of Arizona, Online Education (IEEE, 2022-09)
      What would happen if online course content was produced at television-or even cinematic-level quality? Would students become more engaged? Would they learn more and more deeply? If so, would the gains be worth the expenditure of time and funds that higher video production quality requires? To put it another way: Do investments in video production quality result in measurable increases in students' achievement of learning outcomes and objectives? Questions such as these are at the heart of this preliminary discussion of production value for online content creation, which investigates a grand challenge facing higher education and society generally, as we navigate the spectrum of modalities in a post-pandemic world. This questions that this paper proposes stands at the intersection of educational scholarship, course content creation, student retention and persistence, and the achievement of learning outcomes and objectives. It, therefore, seeks to push forward a model for change and improvement in university education and teaching and learning on our campuses.
    • A Descriptive Study of Speech Breathing in Children With Cerebral Palsy During Two Types of Connected Speech Tasks

      Kovacs, Sydney; Darling-White, Meghan; Department of Speech, Language, and Hearing Sciences, The University of Arizona (American Speech Language Hearing Association, 2022-12-12)
      Purpose: This study examined speech breathing during two connected speech tasks in children with cerebral palsy (CP) and typically developing (TD) peers. Understanding how the respiratory system supports speech production during various speech tasks can help researchers construct appropriate models of speech production and clinicians remediate speech disorders effectively. Method: Four children with CP and four age-and sex-matched TD peers completed two speech tasks, reading and extemporaneous speech. Respiratory kinematic and acoustic data were collected. Dependent variables included utterance length, speech rate, sound pressure level, and lung volume variables. Results: Based on descriptive results, children with CP and speech motor involvement demonstrated reduced utterance length and speech rate, equivalent intensity levels, and changes in lung volume variables indicative of respiratory physiological impairment as compared to their TD peers. However, children with CP and no speech motor involvement exhibited speech production and speech breathing variables in the more typical range. In relation to task effects, the majority of children (CP and TD) produced shorter utterances, slower speech rates, equivalent intensity levels, higher lung volume initiation, termination, excursion, higher percent vital capacity per syllable, and longer inspiratory duration during extemporaneous speech as compared to reading. Conclusions: Two major themes emerged from the data: (a) Children with CP, particularly those with concomitant speech motor involvement, demonstrate different speech production and speech breathing patterns than their TD peers. (b) Speech task impacts speech production and speech breathing variables in both children with CP and their TD peers, but the extemporaneous speech task did not seem to exaggerate group differences.
    • Clinically Relevant Drug Interactions with Monoamine Oxidase Inhibitors

      Edinoff, A.N.; Swinford, C.R.; Odisho, A.S.; Burroughs, C.R.; Stark, C.W.; Raslan, W.A.; Cornett, E.M.; Kaye, A.M.; Kaye, A.D.; College of Medicine-Tucson, University of Arizona (Open Medical Publishing, 2022)
      Monoamine oxidase inhibitors (MAOI) are a class of drugs that were originally developed for the treatment of depression but have since been expanded to be used in management of affective and neurological disorders, as well as stroke and aging-related neurocognitive changes. Ranging from irreversible to reversible and selective to non-selective, these drugs target the monoamine oxidase (MAO) enzyme and prevent the oxidative deamination of various monoamines and catecholamines such as serotonin and dopamine, respectively. Tyramine is a potent releaser of norepinephrine (NE) and is found in high concentrations in foods such as aged cheeses and meats. Under normal conditions, NE is unable to accumulate to toxic levels due to the presence of MAO-A, an enzyme that degrades neurotransmitters, including NE. When MAO-A is inhibited, the capacity to handle tyramine intake from the diet is significantly reduced causing the brain to be vulnerable to overstimulation of postsynaptic adrenergic receptors with as little as 8-10 mg of tyramine ingested and can result in life-threatening blood pressure elevations. In addition to adverse reactions with certain foods, both older and newer MAOIs can negatively interact with both sympathomimetic and serotonergic drugs. In general, patients on a MAOI want to avoid two types of medications: those that can elevate blood pressure via sympathomimetic actions (e.g., phenylephrine and oxymetazoline) and those that can increase serotonin levels via 5-HT reuptake inhibition (e.g., dextromethorphan, chlorpheniramine, and brompheniramine). Illicit drugs that stimulate the central nervous system such as ecstasy (MDMA, 3,4-methylenedioxymethamphetamine) act as serotonin releasers. Patient involvement is also crucial to ensure any interaction within the healthcare setting includes making other providers aware of a MAOI prescription as well as avoiding certain OTC medications that can interact adversely with MAOIs. © 2022, Open Medical Publishing. All rights reserved.
    • A comprehensive review of intraarticular knee injection therapy, geniculate injections, and peripheral nerve stimulation for knee pain in clinical practice

      Poliwoda, S.; Noor, N.; Mousa, B.; Sarwary, Z.; Noss, B.; Urits, I.; Viswanath, O.; Behara, R.; Ulicny, K.; Howe, A.; et al. (Open Medical Publishing, 2022)
      The knee is the most common joint in adults associated with morbidity. Many pathologies are associated with knee damage, such as gout or rheumathoid arthritis, but the primary condition is osteoarthritis (OA). Not only can osteoarthritis cause significant pain, but it also can result in signficant disability as well. Treatment for this condition varies, starting off with oral analgesics and physical therapy to surgical total knee replacmenet. In the gamut of this various treatments, a conservative approach has included intra articular steroid injections. With time, researchers and clinicians determined that other components injected to the knee may additionally provide relief of this condition. In this investigation, we describe different types of knee injections such as platelet-rich plasma (PRP), hyaluronic acid, stem cells, and prolotherapy. Additionally, we describe the role of geniculate knee injections, radiofrequency, and periopheral nerve stimulation. These treatments should be considered for patients with knee pain refractory to conservative therapies. © 2022, Open Medical Publishing. All rights reserved.
    • The Value of Classical Islamic Thoufor Muslims Today

      Lucas, S.; School of Middle Eastern and North African Studies, University of Arizona (International Institute of Islamic Thought, 2020)
      This article challenges the assertion, found in the writings Dr. Taha Jabir Al-Alwani and other Muslim reformers, that Islamic thought declined precipitously in the early centuries of Islam and is of little value to contemporary Muslims. It introduces readers to the sophis-ticated thought of four diverse Muslim thinkers from the 5th/11th century who each wrote about topics that remain important to Muslims today, such as the nature of the soul, ethics, the purpose of knowledge, and spirituality. These thinkers are the philosopher-his-torian Miskawayh, the Sunni Mu‘tazili al-Ḥākim al-Jishumī, the Zahiri Ibn Ḥazm, and the Hadith scholar al-Khaṭīb al-Baghdādī. In addition to drawing specific lessons from these classical thinkers’ writings, the article encourages contemporary Muslims to emulate their practice of reading widely, including works of Muslim phi-losophy and theology, and to appreciate the significant connection they made between the acquisition of knowledge and its application to daily life. © 2020 International Institute of Islamic Though.
    • Future Directions for Digital Literacy Fluency using Cognitive Flexibility Research: A Review of Selected Digital Literacy Paradigms and Theoretical Frameworks

      Caton, A.; Bradshaw-Ward, D.; Kinshuk; Savenye, W.; University of Arizona (Commonwealth of Learning, 2022)
      As learners engage, test, and apply new subject knowledge, they often expend their cognitive capacity on the technological tools designed to capture their learning progress and outcomes. The energy and attention spent on these tools reduces their capacity to engage deeply with new learning concepts. Digital literacy skills require both cognitive and technical skills to develop a learner’s ability to locate, use, and communicate information. Increasingly complex information environments create various barriers for student learning, and as our learning and working industries continue to evolve and integrate technologies, students must overcome these barriers by bridging learning needs and technology expectations. This research explores the value of developing digital literacy to improve learners’ cognitive flexibility by decreasing technological cognitive load and increasing learning fluency. The findings highlight the need for establishing scaffolded digital literacy skills and digital tool selection, and expand college readiness requirements to include digital literacy as a prerequisite skill for learners. © 2022, Commonwealth of Learning. All rights reserved.
    • An Evaluation of Electrostatic Lofting and Subsequent Particle Motion on Bennu

      Hartzell, C.; Zimmerman, M.; Hergenrother, C.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      Electrostatic lofting is the detachment of particles from a surface that occurs if the electrostatic force on the particles is greater than the forces binding the particles to the surface. Electrostatic lofting has been hypothesized to occur on the Moon and observed in the laboratory environment. Because gravity is much weaker on asteroids than on the Moon, the hypothesis of electrostatic lofting has naturally been extended to these smaller airless bodies. We evaluate the feasibility of electrostatic lofting on Bennu using two formulations of the patched charge model. We find that submillimeter particles can be lofted from Bennu’s dayside and, depending on their initial conditions, will reimpact or escape. The size and speed of the predicted electrostatically lofted particles are compared to those of the particle ejection events recently observed on Bennu. We find that dayside electrostatic lofting is not consistent with the size and speed of particles in the largest ejection events observed by the OSIRIS-REx mission. However, the escape of submillimeter particles has implications for the particle size distribution on Bennu’s surface. Additionally, we model particle charging on Bennu’s nightside due to secondary electron emission and find the resulting electrostatic force to be too weak to produce electrostatic lofting on the nightside. © 2022. The Author(s). Published by the American Astronomical Society.
    • Quality Assessment of Stereophotoclinometry as a Shape Modeling Method Using a Synthetic Asteroid

      Weirich, J.; Palmer, E.E.; Daly, M.G.; Barnouin, O.S.; Getzandanner, K.; Kidd, J.N., Jr; Adam, C.D.; Gaskell, R.; Lauretta, D.S.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      The stereophotoclinometry (SPC) software suite has been used to generate global digital terrain models (DTMs) of many asteroids and moons, and was the primary tool used by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission to model the shape of asteroid Bennu. We describe the dedicated preflight testing of SPC for the OSIRIS-REx mission using a synthetic “truth” asteroid model. SPC has metrics that determine the internal consistency of a DTM, but it was not known how these metrics are related to the absolute accuracy of a DTM, which was important for the operational needs of the mission. The absolute accuracy of an SPC-generated DTM cannot be determined without knowing the truth topography. Consequently, we developed a realistic, but synthetic, computer-generated representation of asteroid Bennu, photographed this synthetic truth model in an imaging campaign similar to that planned for the OSIRIS-REx mission, and then generated a global SPC DTM from these images. We compared the SPC DTM, which was represented by a radius every 70 cm across the asteroid surface, to the synthetic truth model to assess the absolute accuracy. We found that the internal consistency can be used to determine the 3D root-mean-square accuracy of the model to within a factor of two of the absolute accuracy. © 2022. The Author(s). Published by the American Astronomical Society.
    • Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA14 during Its 2016 Close Approach

      Kareta, T.; Reddy, V.; Sanchez, J.A.; Harris, W.M.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      The near-Earth comet P/2016 BA14 (PanSTARRS) is a slow-rotating, nearly dormant object, a likely dynamical twin of 252P/LINEAR, and was recently shown to have a mid-infrared spectrum very dissimilar to other comets. Comet BA14 was also recently selected as one of the backup targets for the ESA’s Comet Interceptor, so a clearer understanding of BA14’s modern properties would not just improve our understanding of how comets go dormant but could also aid in planning for a potential spacecraft visit. We present observations of BA14 during its 2016 Earth close approach taken with the NASA Infrared Telescope Facility on two dates, both of which are consistent with direct observations of its nucleus. The reflectance spectrum of BA14 is similar to 67P/Churyumov–Gerasimenko, albeit highly phase-reddened. Thermal emission contaminates the reflectance spectrum at longer wavelengths, which we correct with a new Markov Chain Monte Carlo thermal modeling code. The models suggest that BA14’s visible geometric albedo is pV = 0.01–0.03, consistent with radar observations; its beaming parameter is typical for NEOs observed in its geometry; and its reflectance spectrum is red and linear throughout the H and K bands. It appears very much like a “normal” comet nucleus despite its mid-infrared oddities. A slow loss of fine grains as the object’s activity diminished might help to reconcile some of the lines of evidence, and we discuss other possibilities. A spacecraft flyby past BA14 could get closer to the nucleus than with a more active target, and we highlight some science questions that could be addressed with a visit to a (nearly) dormant comet. © 2022. The Author(s). Published by the American Astronomical Society.
    • NEOWISE Observations of the Potentially Hazardous Asteroid (99942) Apophis

      Satpathy, A.; Mainzer, A.; Masiero, J.R.; Linder, T.; Cutri, R.M.; Wright, E.L.; Pittichová, J.; Grav, T.; Kramer, E.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      Large potentially hazardous asteroids (PHAs) are capable of causing a global catastrophe in the event of a planetary collision. Thus, rapid assessment of such an object’s physical characteristics is crucial for determining its potential risk scale. We treated the near-Earth asteroid (99942) Apophis as a newly discovered object during its 2020–2021 close approach as part of a mock planetary defense exercise. The object was detected by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), and data collected by the two active bands (3.4 and 4.6 μm) were analyzed using thermal and thermophysical modeling. Our results indicate that Apophis is an elongated object with an effective spherical diameter Deff = 340 ± 70 m, a geometric visual albedo pV = 0.31 ± 0.09, and a thermal inertia Γ ∼ 150–2850 J m−2 s-½ K−1 with a best-fit value of 550 J m−2 s-½K−1. NEOWISE “discovery” observations reveal that (99942) Apophis is a PHA that would likely cause damage at a regional level and not a global one. © 2022. The Author(s). Published by the American Astronomical Society.
    • Ground Testing of Digital Terrain Models to Prepare for OSIRIS-REx Autonomous Vision Navigation Using Natural Feature Tracking

      Mario, C.E.; Miller, C.J.; Norman, C.D.; Palmer, E.E.; Weirich, J.; Barnouin, O.S.; Daly, M.G.; Seabrook, J.A.; Lorenz, D.A.; Olds, R.D.; et al. (Institute of Physics, 2022)
      The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft collected a sample from the asteroid Bennu in 2020. This achievement leveraged an autonomous optical navigation approach called Natural Feature Tracking (NFT). NFT provided spacecraft state updates by correlating asteroid surface features rendered from previously acquired terrain data with images taken by the onboard navigation camera. The success of NFT was the culmination of years of preparation and collaboration to ensure that feature data would meet navigation requirements. This paper presents the findings from ground testing performed prior to the spacecraft’s arrival at Bennu, in which synthetic data were used to develop and validate the technical approach for building NFT features. Correlation sensitivity testing using synthetic models of Bennu enabled the team to characterize the terrain properties that worked well for feature correlation, the challenges posed by smoother terrain, and the impact of imaging conditions on correlation performance. The team found that models constructed from image data by means of stereophotoclinometry (SPC) worked better than those constructed from laser altimetry data, except when test image pixel sizes were more than a factor of 2 smaller than those of the images used for SPC, and when topography was underrepresented and resulted in incorrect shadows in rendered features. Degradation of laser altimetry data related to noise and spatial sampling also led to poor correlation performance. Albedo variation was found to be a key contributor to correlation performance; topographic data alone were insufficient for NFT. © 2022. The Author(s). Published by the American Astronomical Society.
    • Radar and Optical Characterization of Near-Earth Asteroid 2019 OK

      Zambrano-Marin, L.F.; Howell, E.S.; Taylor, P.A.; Marshall, S.E.; Devogèle, M.; Virkki, A.K.; Hickson, D.C.; Rivera-Valentín, E.G.; Venditti, F.C.F.; Giorgini, J.D.; et al. (Institute of Physics, 2022)
      We conducted radar observations of near-Earth asteroid 2019 OK on 2019 July 25 using the Arecibo Observatory S-band (2380 MHz, 12.6 cm) planetary radar system. Based on Arecibo and optical observations the apparent diameter is between 70 and 130 m. Combined with an absolute magnitude of H = 23.3 ± 0.3, the optical albedo of 2019 OK is likely between 0.05 and 0.17. Our measured radar circular polarization ratio of μC = 0.33 ± 0.03 indicates 2019 OK is likely not a V- or E-type asteroid and is most likely a C- or S-type. The measured radar echo bandwidth of 39 ± 2 Hz restricts the apparent rotation period to be approximately between 3 minutes (0.049 hr, D = 70 m) and 5 minutes (0.091 h, D = 130 m). Together, the apparent diameter and rotation period suggest that 2019 OK is likely not a rubble-pile body bound only by gravity. 2019 OK is one of a growing number of fast-rotating near-Earth asteroids that require some internal strength to keep them from breaking apart. © 2022. The Author(s). Published by the American Astronomical Society.
    • Ring Seismology of the Ice Giants Uranus and Neptune

      A’Hearn, J.A.; Hedman, M.M.; Mankovich, C.R.; Aramona, H.; Marley, M.S.; Department of Planetary Sciences, University of Arizona; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      We assess the prospect of using ring seismology to probe the interiors of the ice giants Uranus and Neptune. We do this by calculating normal-mode spectra for different interior models of Uranus and Neptune using the stellar oscillation code GYRE. These spectra provide predictions of where in these planets’ ring systems the effects of interior oscillations might be detected. We find that f-mode resonances with azimuthal order m = 2 or 7 ≼ m ≼ 19 fall among the inner rings (6, 5, 4, α, and β) of Uranus, while f-mode resonances with 2 ≼ m ≼ 12 fall in the tenuous ζ ring region. In addition, f-mode resonances with m = 2 or 6 ≼ m ≼ 13 may give azimuthal structure to Neptune’s tenuous Galle ring. We also find that g-mode resonances may fall in the middle to outer rings of these planets. Although an orbiter is most likely required to confirm the association between any waves in the rings and planetary normal modes, the diversity of normal-mode spectra implies that identification of just one or two modes in the rings of Uranus or Neptune would eliminate a variety of interior models and thus aid in the interpretation of Voyager observations and future spacecraft measurements. © 2022. The Author(s). Published by the American Astronomical Society.
    • Juno Spacecraft Measurements of Jupiter’s Gravity Imply a Dilute Core

      Militzer, B.; Hubbard, W.B.; Wahl, S.; Lunine, J.I.; Galanti, E.; Kaspi, Y.; Miguel, Y.; Guillot, T.; Moore, K.M.; Parisi, M.; et al. (Institute of Physics, 2022)
      The Juno spacecraft measured Jupiter’s gravity field and determined the even and odd zonal harmonics, Jn, with unprecedented precision. However, interpreting these observations has been a challenge because it is difficult to reconcile the unexpectedly small magnitudes of the moments J4 and J6 with conventional interior models that assume a large, distinct core of rock and ice. Here we show that the entire set of gravity harmonics can be matched with models that assume an ab initio equation of state, wind profiles, and a dilute core of heavy elements that are distributed as far out as 63% of the planet’s radius. In the core region, heavy elements are predicted to be distributed uniformly and make up only 18% by mass because of dilution with hydrogen and helium. Our models are consistent with the existence of primary and secondary dynamo layers that will help explain the complexity of the observed magnetic field. © 2022. The Author(s).
    • Arecibo Planetary Radar Observations of Near-Earth Asteroids: 2017 December–2019 December

      Virkki, A.K.; Marshall, S.E.; Venditti, F.C.F.; Zambrano-Marín, L.F.; Hickson, D.C.; McGilvray, A.; Taylor, P.A.; Rivera-Valentín, E.G.; Devogèle, M.; Díaz, E.F.; et al. (Institute of Physics, 2022)
      We successfully observed 191 near-Earth asteroids using the Arecibo Observatory’s S-band planetary radar system from 2017 December through 2019 December. We present radar cross sections for 167 asteroids; circular-polarization ratios for 112 asteroids based on Doppler-echo-power spectra measurements; and radar albedos, constraints on size and spin periods, and surface-feature and shape evaluation for 37 selected asteroids using delay-Doppler radar images with a range resolution of 75 m or finer. Out of 33 asteroids with an estimated effective diameter of at least 200 m and sufficient image quality to give clues of the shape, at least 4 (∼12%) are binary asteroids, including 1 equal-mass binary asteroid, 2017 YE5, and at least 10 (∼30%) are contact-binary asteroids. For 5 out of 112 asteroids with reliable measurements in both circular polarizations, we measured circular-polarization ratios greater than 1.0, which could indicate that they are E-type asteroids, while the mean and the 1σ standard deviation were 0.37 ± 0.23. Further, we find a mean opposite-sense circular-polarization radar albedo of 0.21 ± 0.11 for 41 asteroids (0.19 ± 0.06 for 11 S-complex asteroids). We identified two asteroids, 2011 WN15 and (505657) 2014 SR339, as possible metal-rich objects based on their unusually high radar albedos, and discuss possible evidence of water ice in 2017 YE5. © 2022. The Author(s). Published by the American Astronomical Society.
    • Burial Depths of Extensive Shallow Cryptomaria in the Lunar Schiller–Schickard Region

      Bramson, A.M.; Carter, L.M.; Patterson, G.W.; Sori, M.M.; Morgan, G.A.; Jozwiak, L.M.; Nypaver, C.A.; Cahill, J.T.S.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      Quantifying the volumes and geologic nature of lunar volcanic eruptions is important for constraining the thermal and geologic evolution of the Moon. Cryptomaria are effusive, basaltic lava flows on the Moon that were subsequently buried, and therefore hidden, by higher-albedo basin and crater ejecta. Radar offers the ability to probe the subsurface for geologic units not otherwise apparent at the surface. We use Arecibo/Green Bank Observatory and Lunar Reconnaissance Orbiter Mini-RF radar data sets to characterize maria and cryptomaria within the Schiller–Schickard region. We find significant variability in the radar backscatter across the region that does not correspond to previously mapped boundaries of maria and cryptomaria in the literature. We use the characteristic low backscatter (due to the attenuating nature in radio waves of some basaltic minerals) to analyze the distribution of cryptomaria. We use the reduction in radar backscatter to estimate burial depths of cryptomaria across the area. We present a new map of Schiller–Schickard cryptomaria and the local variability in the thicknesses of the light plains that bury the basalts. We find burial depths ranging from >100 m in the deepest areas to just a few to tens of meters in areas with shallow cryptomaria (particularly prominent in the southeast). These areas are generally contiguous with maria, allowing us to track mare lava flow units into the subsurface at mare/highland margins. We propose that ∼67% of the region contains surface or buried basaltic volcanism, which represents over twice (2.7× increase) the areal extent of cryptomaria reported in previous studies. © 2022. The Author(s). Published by the American Astronomical Society.
    • Physical Characterization of Near-Earth Asteroid (52768) 1998 OR2: Evidence of Shock Darkening/Impact Melt

      Battle, A.; Reddy, V.; Sanchez, J.A.; Sharkey, B.; Pearson, N.; Bowen, B.; Lunar and Planetary Laboratory, University of Arizona (Institute of Physics, 2022)
      We conducted photometric and spectroscopic characterization of near-Earth asteroid (52768) 1998 OR2 during a close approach to Earth in 2020 April. Our photometric measurements confirm the rotation period of the asteroid to be 4.126 ± 0.179 hr, consistent with the previously published value of 4.112 ± 0.001 hr. By combining our visible spectroscopic measurements (0.45–0.93 μm) with archival MITHNEOS near-infrared spectra (0.78–2.49 μm), we classify the asteroid as an Xn-type in the Bus–DeMeo taxonomy. The combined spectrum shows two weak absorption bands: Band I at 0.926 ± 0.003 μm and Band II at 2.07 ± 0.02 μm, with band depths of 4.5% ± 0.15% and 4.0% ± 0.21%, respectively. The band area ratio is 1.13 ± 0.05. These spectral band parameters plot at the tip of the S(IV) region of the Gaffey S-asteroid subtypes plot, suggesting an affinity to ordinary chondrite meteorites. We calculated the chemistry of olivine and pyroxene using the Band I center to be 20.1 ± 2.3 mol% fayalite and 18.2 ± 1.5 mol% ferrosilite, consistent with H-chondrites. Principal component analysis of 1998 OR2’s combined visible–near-IR spectrum falls on the C/X-complex side of the α-line, near the end of the shock-darkening trend, consistent with its weak absorption bands (band depth <5%). We use an areal mixing model with lab measurements of the shock-darkened H5 chondrite, Chergach, to constrain the amount of shock-darkened material on the asteroid’s surface at ∼63% dark lithology and ∼37% light lithology. © 2022. The Author(s). Published by the American Astronomical Society.