Now showing items 8155-8174 of 12955

    • OASIS architecture: Key features

      Arenberg, J.W.; Villarreal, M.N.; Yamane, J.; Yu, T.; Lazear, J.; Pohner, J.; Sangalis, M.; Jackson, S.L.; Morse, E.; Tyler, R.; et al. (SPIE, 2021)
      Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a mission concept being developed in preparation for the 2021 MidEX Announcement of Opportunity. This paper describes the key features of the OASIS architecture as they are currently understood. OASIS’s choice of a large inflatable primary reflector results in large collection areas at very high mass efficiency enabling the science mission. We describe the spacecraft bus, based on Northrop Grumman’s LEOstar-2, and the receiver, a heritage design based on the GUSTO balloon heterodyne system. We also discuss the observing strategy and pointing requirements from its planned L1 location. Particular emphasis is placed on challenges to the design, such as momentum management, balancing consumable mass allocations, thermal management, and testing. © 2021 SPIE.
    • Objective assessment of spectacle wear in infants and toddlers using a wearable sensor

      Miller, J.M.; Dennis, L.K.; Hsu, C.-H.; Harvey, E.M.; Department of Ophthalmology and Vision Science, The University of Arizona; Mel and Enid Zuckerman College of Public Health, The University of Arizona; James C. Wyant College of Optical Sciences, The University of Arizona (Association for Research in Vision and Ophthalmology Inc., 2021)
      Purpose: To assess the feasibility of using a thermal microsensor to monitor spectacle wear in infants and toddlers, to determine the inter-method reliability of two methods of estimating spectacle wear from sensor data, and to validate sensor estimates of wear. Methods: Fourteen children, 3 to <48 months of age, and one adult were provided pediatric spectacles containing their spectacle prescription. A thermal microsensor attached to the spectacle headband recorded date, time, and ambient temperature every 15 minutes for 14 days. Parents were asked for daily spectacle wear reports, and the adult recorded wear using a smartphone app. Sensor data were dichotomized (wear/non-wear) using two methods: temperature threshold (TT) and human judgment (HJ). Kappa statistics assessed inter-method reliability (child data) and accuracy (adult data). Results: Data from two child participants were excluded (one because of corrupted sensor data and the other because of no parent log data). Sensor data were collected more reliably than parent wear reports. The TT and HJ analysis of child data yielded similar reliability. Adult sensor data scored using the HJ method provided more valid estimates of wear than the TT method (κ = 0.94 vs. 0.78). Conclusions: We have demonstrated that it is feasible to deduce periods of spectacle wear using a thermal data logger and that the sensor is tolerated by children. Translational Relevance: Results indicate that it is feasible to use a thermal microsensor to measure spectacle wear for use in clinical monitoring or for research on spectacle treatment in children under 4 years of age. © 2021 The Authors.
    • Objective assessment of the effects of tumor motion in radiation therapy

      Ding, Yijun; Barrett, Harrison H; Kupinski, Matthew A; Vinogradskiy, Yevgeniy; Miften, Moyed; Jones, Bernard L; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Med Imaging (WILEY, 2019-07-01)
      Purpose Internal organ motion reduces the accuracy and efficacy of radiation therapy. However, there is a lack of tools to objectively (based on a medical or scientific task) assess the dosimetric consequences of motion, especially on an individual basis. We propose to use therapy operating characteristic (TOC) analysis to quantify the effects of motion on treatment efficacy for individual patients. We demonstrate the application of this tool with pancreatic stereotactic body radiation therapy (SBRT) clinical data and explore the origin of motion sensitivity. Methods The technique is described as follows. (a) Use tumor-motion data measured from patients to calculate the motion-convolved dose of the gross tumor volume (GTV) and the organs at risk (OARs). (b) Calculate tumor control probability (TCP) and normal tissue complication probability (NTCP) from the motion-convolved dose-volume histograms. (c) Construct TOC curves from TCP and NTCP models. (d) Calculate the area under the TOC curve (AUTOC) and use it as a figure of merit for treatment efficacy. We used tumor motion data measured from patients to calculate the relation between AUTOC and motion magnitude for 25 pancreatic SBRT treatment plans. Furthermore, to explore the driving factor of motion sensitivity of a given plan, we compared the dose distribution of motion-sensitive plans and motion-robust plans and studied the dependence of motion sensitivity to motion directions. Results Our technique is able to recognize treatment plans that are sensitive to motion. Under the presence of motion, the treatment efficacy of some plans changes from providing high tumor control and low risks of complications to providing no tumor control and high risks of side effects. Several treatment plans experience falloffs in AUTOC at a smaller magnitude of motion than other plans. In our dataset, a potential indicator of a motion-sensitive treatment plan is that the duodenum is in proximity to the tumor in the SI direction. Conclusions The TOC framework can serve as a tool to quantify the effects of internal organ motion in radiation therapy. With pancreatic SBRT clinical data, we applied this tool to study the change in treatment efficacy induced by motion for individual treatment plans. This framework could potentially be used clinically to understand the effects of motion in an individual patient and to design a patient-specific motion management plan. This framework could also be used in research to evaluate different components of the treatment process, such as motion-management techniques, treatment-planning algorithms, and treatment margins.
    • Objective Climatological Analysis of Extreme Weather Events in Arizona during the North American Monsoon

      Mazon, Jeremy J.; Castro, Christopher L.; Adams, David K.; Chang, Hsin-I; Carrillo, Carlos M.; Brost, John J.; Univ Arizona, Dept Hydrol & Atmospher Sci (AMER METEOROLOGICAL SOC, 2016-11)
      Almost one-half of the annual precipitation in the southwestern United States occurs during the North American monsoon (NAM). Given favorable synoptic-scale conditions, organized monsoon thunderstorms may affect relatively large geographic areas. Through an objective analysis of atmospheric reanalysis and observational data, the dominant synoptic patterns associated with NAM extreme events are determined for the period from 1993 to 2010. Thermodynamically favorable extreme-weather-event days are selected on the basis of atmospheric instability and precipitable water vapor from Tucson, Arizona, rawinsonde data. The atmospheric circulation patterns at 500 hPa associated with the extreme events are objectively characterized using principal component analysis. The first two dominant modes of 500-hPa geopotential-height anomalies of the severe-weather-event days correspond to type-I and type-II severe-weather-event patterns previously subjectively identified by Maddox et al. These patterns reflect a positioning of the monsoon ridge to the north and east or north and west, respectively, from its position in the "Four Corners" region during the period of the climatological maximum of monsoon precipitation from mid-July to mid-August. An hourly radar gauge precipitation product shows evidence of organized, westward-propagating convection in Arizona during the type-I and type-II severe weather events. This new methodological approach for objectively identifying severe weather events may be easily adapted to inform operational forecasting or analysis of gridded climate data.
    • Objective fall risk detection in stroke survivors using wearable sensor technology: a feasibility study

      Taylor-Piliae, Ruth E.; Mohler, M. Jane; Najafi, Bijan; Coull, Bruce M.; University of Arizona (TAYLOR & FRANCIS LTD, 2016-03-15)
      Background: Stroke survivors often have persistent neural deficits related to motor function and sensation, which increase their risk of falling, most of which occurs at home or in community settings. The use of wearable technology to monitor fall risk and gait in stroke survivors may prove useful in enhancing recovery and/or preventing injuries. Objective: Determine the feasibility of using wearable technology (PAMSys (TM)) to objectively monitor fall risk and gait in home and community settings in stroke survivors. Methods: In this feasibility study, we used the PAMSys to identify fall risk indicators (postural transitions: duration in seconds, and number of unsuccessful attempts), and gait (steps, speed, duration) for 48 hours during usual daily activities in stroke survivors (n=10) compared to age-matched controls (n=10). A questionnaire assessed device acceptability. Results: Stroke survivors mean age was 70 +/- 8 years old, were mainly Caucasian (60%) women (70%), and not significantly different than the age-matched controls (all P-values >0.20). Stroke survivors (100%) reported that the device was comfortable to wear, didn't interfere with everyday activities, and were willing to wear it for another 48 hours. None reported any difficulty with the device while sleeping, removing/putting back on for showering or changing clothes. When compared to controls, stroke survivors had significantly worse fall risk indicators and walked less (P<0.05). Conclusion: Stroke survivors reported high acceptability of 48 hours of continuous PAMSys monitoring. The use of in-home wearable technology may prove useful in monitoring fall risk and gait in stroke survivors, potentially enhancing recovery.
    • Objectively Measured Social Integration Is Associated With an Immune Risk Phenotype Following Marital Separation

      Hasselmo, Karen; Mehl, Matthias R; Tackman, Allison M; Carey, Angela L; Wertheimer, Anne M; Stowe, Raymond P; Sbarra, David A; Univ Arizona, Dept Psychol; Univ Arizona, Dept Med, Div Geriatr Gen Internal Med & Palliat Med (OXFORD UNIV PRESS INC, 2018-02)
      Background Close relationships play an integral role in human development, and robust evidence links marital separation and divorce to poor health outcomes. Social integration may play a key role in this association. In many ways, the study of marital separation and divorce provides an ideal model system for a more complete understanding of the association between life stress and physical health. Purpose The current study investigated associations among objectively measured social integration, psychological distress, and biomarkers of immune health in recently separated adults (N = 49). Methods We collected four measures of immune functioning-interleukin-6, C-reactive protein, and antibody titers to latent cytomegalovirus and Epstein-Barr virus-that were combined to yield a viral-Immune Risk Profile. To assess how variability in social integration is associated with immunological correlates following the end of a marriage, we incorporated observational ecological momentary assessment data using a novel methodology (the Electronically Activated Recorder). Results We found that objectively measured social behaviors are associated with concurrent viral-Immune Risk Profile scores over and above the effects of psychological distress and that psychological distress may be linked to biomarkers of immune health through social integration. Conclusions This research expands current knowledge of biomarkers of immune health after divorce and separation and includes a new methodology for objective measures of social engagement.
    • Les objets techniques au prisme du cycle hydrosocial : renouveaux théoriques et empiriques

      Germaine, Marie-Anne; Blanchon, David; Temple-Boyer, Élise; Fofack-Garcia, Rhoda; Univ Arizona (RESEAU DEVELOPPEMENT DURABLE & TERRITOIRES FRAGILES, 2019-12-20)
      This special issue entitled "Technical objects at the prism of hydrosocial cycle : new theoretical and empirical approaches" presents new insights concerning water-society relations in social sciences. It is characterized by interdisciplinary approaches and engages with two main theoretical frameworks : science and technology studies and political ecology. Both are indeed mobilized in order to deepen the analysis of the dialectical relation between technical objects and hydrosocial systems, by using the concept of hydrosocial cycle. Our aim is to explain how "infrastructure" and "apparatus" forge and transform water-society interrelations, reshape them and modify their functioning. But also how the hydrosocial cycle, in return, sets out particular forms of infrastructure and apparatus. This paper firstly introduces the theoretical and epistemological debates linked to this special issue. And then it presents the thirteen papers gathered in this special issue, which, based on empirical studies, offer different uses of hydrosocial cycle approach to investigate water/society dialectical relations.

      Satyapal, S.; Secrest, Nathan J.; Rothberg, B.; O’Connor, J. A.; Ellison, Sara L.; Hickox, Ryan C.; Constantin, A.; Gliozzi, M.; Rosenberg, and J. L.; Univ Arizona, LBT Observ (IOP PUBLISHING LTD, 2016-08-08)
      There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3 sigma level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of L2-10 (keV) = (1.1 +/- 0.4) x 10(40) erg s(-1). Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of N-H > 10(24) cm(-2). The hard X-ray luminosity of the putative AGN corrected for absorption is L2-10 keV similar to 3 x 10(42) erg s(-1), which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of L-bol 6 x 10(43)-3 x 10(44) erg s(-1). and a lower mass limit for the black hole of M-BH similar or equal to 2 x 10(6) M-circle dot, based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of similar to 2.0 x 10(10) M-circle dot and an above solar metallicity (12 + logO/H = 9.11), typical of our WISE-selected bulgeless galaxy. sample. While collectively. these observations suggest the presence of an AGN, we caution that identifying obscured AGNs in the low-luminosity regime is challenging. and often requires multiwavelength observations. These observations suggest that low-luminosity AGNs can be heavily obscured and reside in optically quiescent galaxies, adding to the growing body of evidence that the fraction of bulgeless galaxies with accreting black holes may be significantly underestimated based on optical studies.
    • Observable predictions for massive-neutrino cosmologies with model-independent dark energy

      Diaz Rivero, Ana; Miranda, V.; Dvorkin, Cora; Univ Arizona, Steward Observ, Dept Astron (AMER PHYSICAL SOC, 2019-09-04)
      We investigate the bounds on the sum of neutrino masses in a cosmic-acceleration scenario where the equation of state w(z) of dark energy (DE) is constructed in a model-independent way, using a basis of principal components (PCs) that are allowed to cross the phantom barrier w(z)=−1. We find that the additional freedom provided to w(z) means the DE can undo changes in the background expansion induced by massive neutrinos at low redshifts. This has two significant consequences: (1) it leads to a substantial increase in the upper bound for the sum of the neutrino masses (Mν<0.33–0.55 eV at the 95% C.L. depending on the data sets and number of PCs included) compared to studies that choose a specific parametrization for w(z); and (2) it causes ∼1σ deviations from ΛCDM in the luminosity distance and the Hubble expansion rate at higher redshifts (z≳2), where the contribution of DE is subdominant and there is little constraining data. The second point consequently means that there are also observable deviations in the shear power spectrum and in the matter power spectrum at low redshift, since the clustering of matter throughout cosmic time depends on the expansion rate. This provides a compelling case to pursue high-z BAO and SN measurements as a way of disentangling the effects of neutrinos and dark energy. Finally, we find that the additional freedom given to the dark energy component has the effect of lowering S8 with respect to ΛCDM.
    • Observable Predictions from Perturber-coupled High-eccentricity Tidal Migration of Warm Jupiters

      Jackson, J.M.; Dawson, R.I.; Shannon, A.; Petrovich, C.; Steward Observatory, University of Arizona (American Astronomical Society, 2021)
      The origin of warm Jupiters (gas giant planets with periods between 10 and 200 days) is an open question in exoplanet formation and evolution. We investigate a particular migration theory in which a warm Jupiter is coupled to a perturbing companion planet that excites secular eccentricity oscillations in the warm Jupiter, leading to periodic close stellar passages that can tidally shrink and circularize its orbit. If such companions exist in warm Jupiter systems, they are likely to be massive and close-in, making them potentially detectable. We generate a set of warm Jupiter-perturber populations capable of engaging in high-eccentricity tidal migration and calculate the detectability of the perturbers through a variety of observational metrics. We show that a small percentage of these perturbers should be detectable in the Kepler light curves, but most should be detectable with precise radial velocity measurements over a 3 month baseline and Gaia astrometry. We find these results to be robust to the assumptions made for the perturber parameter distributions. If a high-precision radial velocity search for companions to warm Jupiters does not find evidence of a significant number of massive companions over a 3 month baseline, it will suggest that perturber-coupled high-eccentricity migration is not the predominant delivery method for warm Jupiters. © 2021. The American Astronomical Society. All rights reserved..
    • Observable shape of black hole photon rings

      Gralla, Samuel E.; Lupsasca, Alexandru; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2020-12-01)
      Motivated by the prospect of measuring a black hole photon ring, in previous work we explored the interferometric signature produced by a bright, narrow curve in the sky. interferometric observations of such a curve measure its "projected position function" r . (n) over cap, where r parametrizes the curve and (n) over cap denotes its unit normal vector. In this paper, we show by explicit construction that a curve can be fully reconstructed from its projected position, completing the argument that space interferometry can in principle determine the detailed photon ring shape. In practice, near-term observations may be limited to the visibility amplitude alone, which contains incomplete shape information: for convex curves, the amplitude only encodes the set of projected diameters (or "widths") of the shape. We explore the freedom in reconstructing a convex curve from its widths, giving insight into the shape information probed by technically plausible future astronomical measurements. Finally, we consider the Kerr "critical curve" in this framework and present some new results on its shape. We analytically show that the critical curve is an ellipse at small spin or inclination, while at extremal spin it becomes the convex hull of a Cartesian oval. We find a simple oval shape, the "phoval," which reproduces the critical curve with high fidelity over the whole parameter range.
    • Observation and confirmation of nine strong-lensing systems in Dark Energy Survey Year 1 data

      Nord, B; Buckley-Geer, E; Lin, H; Kuropatkin, N; Collett, T; Tucker, D L; Diehl, H T; Agnello, A; Amara, A; Abbott, T M C; et al. (OXFORD UNIV PRESS, 2020-01-28)
      We describe the observation and confirmation of nine new strong gravitational lenses discovered in Year 1 data from the Dark Energy Survey (DES). We created candidate lists based on (i) galaxy group and cluster samples, and (ii) photometrically selected galaxy samples. We selected 46 candidates through visual inspection and then used the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope to acquire a spectroscopic follow-up of 21 of these candidates. Through an analysis of these spectroscopic follow-up data, we confirmed nine new lensing systems and rejected two candidates, and the analysis was inconclusive on 10 candidates. For each of the confirmed systems, our report measured spectroscopic properties, estimated source image-lens separations, and estimated enclosed masses as well. The sources that we targeted have an i-band surface brightness range of i(SB) similar to 22-24 mag arcsec(-2) and a spectroscopic redshift range of z(spec) similar to 0.8-2.6. The lens galaxies have a photometric redshift range of z(lens) similar to 0.3-0.7. The lensing systems range in source image-lens separation from 2 to 9 arcsec and in enclosed mass from 10(12) to 10(13) M-circle dot.

      Nord, B.; Buckley-Geer, E.; Lin, H.; Diehl, H. T.; Helsby, J.; Kuropatkin, N.; Amara, A.; Collett, T.; Allam, S.; Caminha, G. B.; et al. (IOP PUBLISHING LTD, 2016-08-05)
      We report the observation and confirmation of the first group-and cluster-scale strong gravitational lensing systems found in Dark Energy Survey data. Through visual inspection of data from the Science Verification season, we identified 53 candidate systems. We then obtained spectroscopic follow-up of 21 candidates using the Gemini Multi-object Spectrograph at the Gemini South telescope and the Inamori-Magellan Areal Camera and Spectrograph at the Magellan/Baade telescope. With this follow-up, we confirmed six candidates as gravitational lenses: three of the systems are newly discovered, and the remaining three were previously known. Of the 21 observed candidates, the remaining 15 either were not detected in spectroscopic observations, were observed and did not exhibit continuum emission (or spectral features), or were ruled out as lensing systems. The confirmed sample consists of one group-scale and five galaxy-cluster-scale lenses. The lensed sources range in redshift z similar to 0.80-3.2 and in i-band surface brightness i(SB) similar to 23-25 mag arcsec(-2) (2 '' aperture). For each of the six systems, we estimate the Einstein radius theta(E) and the enclosed mass M-enc, which have ranges theta(E) similar to 5 ''-9 '' and M-enc similar to 8 x 10(12) to 6 x 10(13)M(circle dot), respectively.
    • Observation and Measurement of Forward Proton Scattering in Association with Lepton Pairs Produced via the Photon Fusion Mechanism at ATLAS

      ATLAS Collaboration; Department of Physics, University of Arizona (American Physical Society, 2020)
      The observation of forward proton scattering in association with lepton pairs (e+e-+p or μ+μ-+p) produced via photon fusion is presented. The scattered proton is detected by the ATLAS Forward Proton spectrometer, while the leptons are reconstructed by the central ATLAS detector. Proton-proton collision data recorded in 2017 at a center-of-mass energy of s=13 TeV are analyzed, corresponding to an integrated luminosity of 14.6 fb-1. A total of 57 (123) candidates in the ee+p (μμ+p) final state are selected, allowing the background-only hypothesis to be rejected with a significance exceeding 5 standard deviations in each channel. Proton-tagging techniques are introduced for cross-section measurements in the fiducial detector acceptance, corresponding to σee+p=11.0±2.6(stat)±1.2(syst)±0.3(lumi) and σμμ+p=7.2±1.6(stat)±0.9(syst)±0.2(lumi) fb in the dielectron and dimuon channel, respectively. © 2020 CERN.
    • Observation of Discrete Floquet Time Crystals in Periodically Driven Acoustic Bubbles

      Deymier, P.; Runge, K.; Department of Materials Science and Engineering, University of Arizona (MDPI, 2022)
      We show experimentally and theoretically that the translation dynamics of acoustic bubbles in an acoustic standing wave field exhibit all the attributes of a discrete time crystal, the dynamics of which is described by Mathieu’s equation. Individual bubbles and synchronized bubbles in a self-organized chain undergo emergent slow persistent oscillations. The period of the emergent oscillations is longer than that of the driving acoustic wave by three orders of magnitude, therefore, breaking the discrete time translation symmetry of the driver. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
    • Observation of Electroweak Production of a Same-Sign W Boson Pair in Association with Two Jets in pp Collisions root s=13 TeV with the ATLAS Detector

      Berlendis, S; Cheu, E; Delitzsch, C M; Johns, K A; Jones, S; Lampl, W; LeBlanc, M; Leone, R; Loch, P; Nayyar, R; et al. (AMER PHYSICAL SOC, 2019-10-15)
      This Letter presents the observation and measurement of electroweak production of a same-sign W boson pair in association with two jets using 36.1 fb(-1) of proton-proton collision data recorded at a center-of-mass energy root s = 13 TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69 +/- 7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial signal cross section is sigma(f)(id) = 2.89(-0.48)(+0.51)(stat)(-0.28)(+0.29)(syst) fb.
    • Observation of electroweak W(+/-)Z boson pair production in association with two jets in pp collisions at root s=13 TeV with the ATLAS detector

      Berlendis, S.; Cheu, E.; Delitzsch, C.M.; Johns, K.A.; Jones, S., I; Lampl, W.; LeBlanc, M.; Leone, R.; Loch, P.; Nayyar, R.; et al. (ELSEVIER SCIENCE BV, 2019-06-10)
      An observation of electroweak W(+/-)Z production in association with two jets in proton-proton collisions is presented. The data collected by the ATLAS detector at the Large Hadron Collider in 2015 and 2016 at a centre-of-mass energy of root s = 13 TeV are used, corresponding to an integrated luminosity of 36.1 fb(-1). Events containing three identified leptons, either electrons or muons, and two jets are selected. The electroweak production of W(+/-)Z bosons in association with two jets is measured with an observed significance of 5.3 standard deviations. A fiducial cross-section for electroweak production including interference effects and for a single leptonic decay mode is measured to be sigma(WZjj-EW) = 0.57(-0.13)(+0.14) (stat.) (+0.07)(-0.06) (syst.) fb. Total and differential fiducial cross-sections of the sum of W(+/-)Zjj electroweak and strong productions for several kinematic observables are also measured. (C) 2019 The Author(s). Published by Elsevier B.V.
    • Observation of elliptically polarized light from total internal reflection in bubbles

      Miller, Sawyer; Ding, Yitian; Jiang, Linan; Tu, Xingzhou; Pau, Stanley; Univ Arizona, James C Wyant Coll Opt Sci (NATURE PUBLISHING GROUP, 2020-05-26)
      Bubbles are ubiquitous in the natural environment, where different substances and phases of the same substance forms globules due to differences in pressure and surface tension. Total internal reflection occurs at the interface of a bubble, where light travels from the higher refractive index material outside a bubble to the lower index material inside a bubble at appropriate angles of incidence, which can lead to a phase shift in the reflected light. Linearly polarized skylight can be converted to elliptically polarized light with efficiency up to 53% by single scattering from the water-air interface. Total internal reflection from air bubble in water is one of the few sources of elliptical polarization in the natural world. Stationary and dynamic scenes of air bubbles in water in both indoor and outdoor settings are studied using an imaging polarimeter. Our results are important for studies in fluid dynamics, remote sensing, and polarimetry.
    • Observation of Gravitational Waves from Two Neutron Star-Black Hole Coalescences

      LIGO Scientific Collaboration; Virgo Collaboration; KAGRA Collaboration; University of Arizona (American Astronomical Society, 2021)
      We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star-black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO-Virgo detectors. The source of GW200105 has component masses, whereas the source of GW200115 has component masses and (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are and, respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of when assuming that GW200105 and GW200115 are representative of the NSBH population or under the assumption of a broader distribution of component masses. © 2021. The Author(s). Published by the American Astronomical Society.
    • Observation of Light-by-Light Scattering in Ultraperipheral Pb plus Pb Collisions with the ATLAS Detector

      Berlendis, S.; Cheu, E.; Delitzsch, C. M.; Johns, K. A.; Jones, S., I; Lampl, W.; LeBlanc, M.; Leone, R.; Loch, P.; Rutherfoord, J. P.; et al. (AMER PHYSICAL SOC, 2019-07-31)
      This Letter describes the observation of the light-by-light scattering process, gamma gamma -> gamma gamma, in Pb + Pb collisions at root S-NN = 5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb(-1), collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy E-T(gamma) > 3 GeV and pseudorapidity vertical bar eta(gamma)vertical bar < 2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12 +/- 3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78 +/- 13(stat) +/- 7(syst) +/- 3(lumi) nb.