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Recent Submissions

  • Risk and performance of bonds sponsored by private equity firms

    Cao, Xiaping; Chan, Konan; Kahle, Kathleen; Univ Arizona, Eller Coll Management (ELSEVIER SCIENCE BV, 2018-08)
    The bond market is an important source of financing for Private Equity (PE) sponsored transactions. Using the methodology suggested by Bessembinder et al. (2009), we find that PE-sponsored bonds under perform comparable benchmarks. This is especially true for bonds with credit ratings below investment grade and those issued in hot bond markets. Furthermore, bonds sponsored by more experienced PE groups (PEGs) underperform bonds associated with less experienced PE groups, while bonds backed by investment bank-affiliated PEGs underperform bonds sponsored by other PEGs. These findings highlight the risk and return relationship in the high-yield bond market related to leveraged buyouts (LBOs) and PEGs. (C) 2018 Elsevier B.V. All rights reserved.
  • Profiling caregivers: Hormonal variation underlying allomaternal care in wild red-bellied lemurs, Eulemur rubriventer

    Tecot, Stacey R.; Baden, Andrea L.; Univ Arizona, Sch Anthropol; Univ Arizona, Lab Evolutionary Endocrinol Primates (PERGAMON-ELSEVIER SCIENCE LTD, 2018-09-01)
    Neuroendocrine evidence suggests that paternal care is mediated by hormonal mechanisms, where hormonal changes in expectant and new fathers facilitate infant care. In species with obligate and extensive paternal care such as humans, androgen levels decline once males are paired and have offspring, and in direct response to offspring care. Facultative infant care is widespread in the Order Primates, but the underlying hormonal mechanisms are largely unknown. We found that wild, red-bellied lemurs living in family groups (two adults and their presumed offspring) varied in the amount of care they provided infants. The more fathers invested in helping infants (measured as a composite of carrying, holding, huddling, grooming, and playing), and specifically the more they huddled and groomed with infants, the higher their fecal androgen (fA) levels, contrary to expectations. Carrying was negatively related to fA levels. Helping by subadults and juveniles was not related to their own fA levels. Elevated fA levels during infant dependence have been observed in other vertebrate species, and are thought to reflect reinvestment in mating rather than investment in dependent offspring. However, red-bellied lemurs do not mate until after infants are weaned, and they have long-term pair-bonds, suggesting that elevated fA levels play a role in offspring care. These results support a growing body of research suggesting that elevated androgen levels do not inhibit protective infant care.
  • Search for Higgs boson decays into pairs of light (pseudo)scalar particles in the gamma gamma jj final state in pp collisions at root s=13 TeV with the ATLAS detector

    Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.; Abeloos, B.; Abidi, S.H.; AbouZeid, O.S.; Abraham, N.L.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Acharya, B.S.; Adachi, S.; Adamczyk, L.; Adelman, J.; Adersberger, M.; Adye, T.; Affolder, A.A.; Afik, Y.; Agheorghiesei, C.; Aguilar-Saavedra, J.A.; Ahmadov, F.; Aielli, G.; Akatsuka, S.; Åkesson, T.P.A.; Akilli, E.; Akimov, A.V.; Alberghi, G.L.; Albert, J.; Albicocco, P.; Alconada Verzini, M.J.; Alderweireldt, S.; Aleksa, M.; Aleksandrov, I.N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Ali, B.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S.P.; Allaire, C.; Allbrooke, B.M.M.; Allen, B.W.; Allport, P.P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alshehri, A.A.; Alstaty, M.I.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M.G.; Amadio, B.T.; Amaral Coutinho, Y.; Ambroz, L.; Amelung, C.; Amidei, D.; Amor Dos Santos, S.P.; Amoroso, S.; Anastopoulos, C.; Ancu, L.S.; Andari, N.; Andeen, T.; Anders, C.F.; Anders, J.K.; Anderson, K.J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Angerami, A.; Anisenkov, A.V.; Annovi, A.; Antel, C.; Antonelli, M.; Antonov, A.; Antrim, D.J.A.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J.P.; Araujo Ferraz, V.; Araujo Pereira, R.; Arce, A.T.H.; Ardell, R.E.; Arduh, F.A.; Arguin, J-F.; Argyropoulos, S.; Armbruster, A.J.; Armitage, L.J.; Arnaez, O.; Arnold, H.; Arratia, M.; Arslan, O.; Univ Arizona, Dept Phys (ELSEVIER SCIENCE BV, 2018-07-10)
    This Letter presents a search for exotic decays of the Higgs boson to a pair of new (pseudo) scalar particles, H -> aa, where the a particle has a mass in the range 20-60 GeV, and where one of the a bosons decays into a pair of photons and the other to a pair of gluons. The search is performed in event samples enhanced in vector-boson fusion Higgs boson production by requiring two jets with large invariant mass in addition to the Higgs boson candidate decay products. The analysis is based on the full dataset of pp collisions at root s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 36.7 fb(-1). The data are in agreement with the Standard Model predictions and an upper limit at the 95% confidence level is placed on the production cross section times the branching ratio for the decay H -> aa -> gamma gamma gg. This limit ranges from 3.1 pb to 9.0 pb depending on the mass of the a boson. (C) 2018 The Author. Published by Elsevier B.V.
  • Topologically Protected Helical States in Minimally Twisted Bilayer Graphene

    Huang, Shengqiang; Kim, Kyounghwan; Efimkin, Dmitry K.; Lovorn, Timothy; Taniguchi, Takashi; Watanabe, Kenji; MacDonald, Allan H.; Tutuc, Emanuel; LeRoy, Brian J.; Univ Arizona, Phys Dept (AMER PHYSICAL SOC, 2018-07-17)
    In minimally twisted bilayer graphene, a moire pattern consisting of AB and BA stacking regions separated by domain walls forms. These domain walls are predicted to support counterpropogating topologically protected helical (TPH) edge states when the AB and BA regions are gapped. We fabricate designer moire crystals with wavelengths longer than 50 nm and demonstrate the emergence of TPH states on the domain wall network by scanning tunneling spectroscopy measurements. We observe a double-line profile of the TPH states on the domain walls, only occurring when the AB and BA regions are gapped. Our results demonstrate a practical and flexible method for TPH state network construction.
  • Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data

    Gruen, D.; Friedrich, O.; Krause, E.; DeRose, J.; Cawthon, R.; Davis, C.; Elvin-Poole, J.; Rykoff, E. S.; Wechsler, R. H.; Alarcon, A.; Bernstein, G. M.; Blazek, J.; Chang, C.; Clampitt, J.; Crocce, M.; De Vicente, J.; Gatti, M.; Gill, M. S. S.; Hartley, W. G.; Hilbert, S.; Hoyle, B.; Jain, B.; Jarvis, M.; Lahav, O.; MacCrann, N.; McClintock, T.; Prat, J.; Rollins, R. P.; Ross, A. J.; Rozo, E.; Samuroff, S.; Sánchez, C.; Sheldon, E.; Troxel, M. A.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Drlica-Wagner, A.; Fernandez, E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Giannantonio, T.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jeltema, T.; Kuehn, K.; Kuropatkin, N.; Lima, M.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Menanteau, F.; Miquel, R.; Mohr, J. J.; Plazas, A. A.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; Weller, J.; Zhang, Y.; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2018-07-13)
    We derive cosmological constraints from the probability distribution function (PDF) of evolved large-scale matter density fluctuations. We do this by splitting lines of sight by density based on their count of tracer galaxies, and by measuring both gravitational shear around and counts-in-cells in overdense and underdense lines of sight, in Dark Energy Survey (DES) First Year and Sloan Digital Sky Survey (SDSS) data. Our analysis uses a perturbation theory model [O. Friedrich et al., Phys. Rev. D 98, 023508 (2018)] and is validated using N-body simulation realizations and log-normal mocks. It allows us to constrain cosmology, bias and stochasticity of galaxies with respect to matter density and, in addition, the skewness of the matter density field. From a Bayesian model comparison, we find that the data weakly prefer a connection of galaxies and matter that is stochastic beyond Poisson fluctuations on <= 20 arcmin angular smoothing scale. The two stochasticity models we fit yield DES constraints on the matter density Omega(m) = 0.26(-0.04)(+0.05) and Omega(m) = 0.28(-0.03)(+0.04) that are consistent with each other. These values also agree with the DES analysis of galaxy and shear two-point functions (3x2pt, DES Collaboration et al.) that only uses second moments of the PDF. Constraints on s 8 are model dependent (sigma(8) = 0.97(-0.06)(+0.07) and 0.80(-0.07)(+0.06) for the two stochasticity models), but consistent with each other and with the 3 x 2pt results if stochasticity is at the low end of the posterior range. As an additional test of gravity, counts and lensing in cells allow to compare the skewness S-3 of the matter density PDF to its Lambda CDM prediction. We find no evidence of excess skewness in any model or data set, with better than 25 per cent relative precision in the skewness estimate from DES alone.
  • Density split statistics: Joint model of counts and lensing in cells

    Friedrich, O.; Gruen, D.; DeRose, J.; Kirk, D.; Krause, E.; McClintock, T.; Rykoff, E. S.; Seitz, S.; Wechsler, R. H.; Bernstein, G. M.; Blazek, J.; Chang, C.; Hilbert, S.; Jain, B.; Kovacs, A.; Lahav, O.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; Davis, C.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Drlica-Wagner, A.; Eifler, T. F.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Kuehn, K.; Kuropatkin, N.; Lima, M.; March, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Mohr, J. J.; Nord, B.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Troxel, M. A.; Vikram, V.; Weller, J.; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2018-07-13)
    We present density split statistics, a framework that studies lensing and counts-in-cells as a function of foreground galaxy density, thereby providing a large-scale measurement of both 2-point and 3-point statistics. Our method extends our earlier work on trough lensing and is summarized as follows: given a foreground (low redshift) population of galaxies, we divide the sky into subareas of equal size but distinct galaxy density. We then measure lensing around uniformly spaced points separately in each of these subareas, as well as counts-in-cells statistics (CiC). The lensing signals trace the matter density contrast around regions of fixed galaxy density. Through the CiC measurements this can be related to the density profile around regions of fixed matter density. Together, these measurements constitute a powerful probe of cosmology, the skewness of the density field and the connection of galaxies and matter. In this paper we show how to model both the density split lensing signal and CiC from basic ingredients: a non-linear power spectrum, clustering hierarchy coefficients from perturbation theory and a parametric model for galaxy bias and shot-noise. Using N-body simulations, we demonstrate that this model is sufficiently accurate for a cosmological analysis on year 1 data from the Dark Energy Survey.
  • High-order encoding schemes for floodlight quantum key distribution

    Zhuang, Quntao; Zhang, Zheshen; Shapiro, Jeffrey H.; Univ Arizona, Dept Mat Sci & Engn (AMER PHYSICAL SOC, 2018-07-23)
    Floodlight quantum key distribution (FL-QKD) has realized a 1.3 Gbit/s secret-key rate (SKR) over a 10-dB-loss channel against a frequency-domain collective attack [Quantum Sci. Technol 3, 025007 (2018)]. It achieved this remarkable SKR by means of binary phase-shift keying (BPSK) of multiple optical modes. Moreover, it did so with available technology, and without space-division or wavelength-division multiplexing. In this paper we explore whether replacing FL-QKD's BPSK modulation with a high-order encoding can further increase that protocol's SKR. First, we show that going to K-ary phase-shift keying with K = 32 doublesfrom 2.0 to 4.5 Gbit/sthe theoretical prediction from [Phys. Rev. A 94, 012322 (2016)] for FL-QKD's BPSK SKR on a 50-km-long fiber link. Second, we show that 2d x 2d quadrature amplitude modulation does not offer any SKR improvement beyond what its d = 1 casewhich is equivalent to quadrature phase-shift keyingprovides.
  • Snapshot multi-wavelength interference microscope

    Tian, Xiaobo; Tu, Xingzhou; Zhang, Junchao; Spires, Oliver; Brock, Neal; Pau, Stanley; Liang, Rongguang; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2018-07-09)
    A snapshot multi-wavelength interference microscope is proposed for high-speed measurement of large vertical range discontinuous microstructures and surface roughness. A polarization CMOS camera with a linear micro-polarizer array and Bayer filter accomplishes snapshot multi-wavelength phase-shifting measurement. Four interferograms with pi/2 phase shift are captured at each wavelength for phase measurement, the 2 pi ambiguities are removed by using two or three wavelengths. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
  • Strehl ratio for optical systems with ultrafast illumination

    Gao, Weichuan; Milster, Tom; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2018-07-09)
    We study ultrafast laser pulse properties as they propagate through optical systems. A modified definition of Strehl ratio is used to quantify the chromatic and temporal behavior of ultrafast laser pulses at the optical focus. We propose this parameter as a figure of merit for the design and analysis of optical systems with ultrafast illumination. A simple method to obtain approximate numerical solutions is given with the help of ray tracing software. Effects of monochromatic aberrations and material dispersion up to the second order are discussed. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.
  • Optimal geometry for off-axis, freeform illumination design

    Gannon, Caleb; Univ Arizona, Coll Opt Sci (SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2018-06)
    A thorough investigation into the efficiency and performance of off-axis, freeform illumination systems has been conducted, and a method for arriving at the optimal tilt is established for both reflective and refractive designs. The optimal tilt for refractive designs is determined by minimizing the total light lost due to Fresnel reflections across the lens, while the optimal tilt for reflective designs ensures the source is not obstructing the reflected ray bundle. For uncoated lenses, utilizing the proposed tilt can improve efficiency by more than 150%. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
  • Fast and continuous recording of refreshable holographic stereograms

    Blanche, Pierre-Alexandre; Bigler, Colton; Ka, Jae-Won; Peyghambarian, Nasser; Univ Arizona, Coll Opt Sci (SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2018-06)
    We present a technique to record refreshable holographic stereograms continuously. We eliminated the translation stage that shifts the recording beams back and forth and replaced it with an uninterrupted transparent belt holding holographic lenses. The belt is driven along a perimeter, shifting the lens laterally in front of a photorefractive screen without reversing direction. The holographic lenses focus the object beam onto holographic pixels and are permanently recorded in a thin photopolymer. The photopolymer material is flexible enough for the lenses to follow the curvature of the belt when it goes around the tensioning rollers. The hogel data are uploaded sequentially onto a spatial light modulator to form the object beam. The rotation of the belt in one single direction allows for a continuous operation and a much faster recording speed than with a translation stage that needs to reverse direction at the end of its travel span. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
  • PD-1 Blockade with Cemiplimab in Advanced Cutaneous Squamous-Cell Carcinoma

    Migden, Michael R.; Rischin, Danny; Schmults, Chrysalyne D.; Guminski, Alexander; Hauschild, Axel; Lewis, Karl D.; Chung, Christine H.; Hernandez-Aya, Leonel; Lim, Annette M.; Chang, Anne Lynn S.; Rabinowits, Guilherme; Thai, Alesha A.; Dunn, Lara A.; Hughes, Brett G.M.; Khushalani, Nikhil I.; Modi, Badri; Schadendorf, Dirk; Gao, Bo; Seebach, Frank; Li, Siyu; Li, Jingjin; Mathias, Melissa; Booth, Jocelyn; Mohan, Kosalai; Stankevich, Elizabeth; Babiker, Hani M.; Brana, Irene; Gil-Martin, Marta; Homsi, Jade; Johnson, Melissa L.; Moreno, Victor; Niu, Jiaxin; Owonikoko, Taofeek K.; Papadopoulos, Kyriakos P.; Yancopoulos, George D.; Lowy, Israel; Fury, Matthew G.; Univ Arizona, Ctr Canc (MASSACHUSETTS MEDICAL SOC, 2018-07-26)
    BACKGROUND No systemic therapies have been approved for the treatment of advanced cutaneous squamous-cell carcinoma. This cancer may be responsive to immune therapy, because the mutation burden of the tumor is high and the disease risk is strongly associated with immunosuppression. In the dose-escalation portion of the phase 1 study of cemiplimab, a deep and durable response was observed in a patient with metastatic cutaneous squamous-cell carcinoma. METHODS We report the results of the phase 1 study of cemiplimab for expansion cohorts of patients with locally advanced or metastatic cutaneous squamous-cell carcinoma, as well as the results of the pivotal phase 2 study for a cohort of patients with metastatic disease (metastatic-disease cohort). In both studies, the patients received an intravenous dose of cemiplimab (3 mg per kilogram of body weight) every 2 weeks and were assessed for a response every 8 weeks. In the phase 2 study, the primary end point was the response rate, as assessed by independent central review. RESULTS In the expansion cohorts of the phase 1 study, a response to cemiplimab was observed in 13 of 26 patients (50%; 95% confidence interval [CI], 30 to 70). In the metastatic-disease cohort of the phase 2 study, a response was observed in 28 of 59 patients (47%; 95% CI, 34 to 61). The median follow-up was 7.9 months in the metastatic-disease cohort of the phase 2 study. Among the 28 patients who had a response, the duration of response exceeded 6 months in 57%, and 82% continued to have a response and to receive cemiplimab at the time of data cutoff. Adverse events that occurred in at least 15% of the patients in the metastatic-disease cohort of the phase 2 study were diarrhea, fatigue, nausea, constipation, and rash; 7% of the patients discontinued treatment because of an adverse event. CONCLUSIONS Among patients with advanced cutaneous squamous-cell carcinoma, cemiplimab induced a response in approximately half the patients and was associated with adverse events that usually occur with immune checkpoint inhibitors.
  • LoCuSS: pre-processing in galaxy groups falling into massive galaxy clusters at z = 0.2

    Bianconi, M; Smith, G P; Haines, C P; McGee, S L; Finoguenov, A; Egami, E; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2018-01)
    We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via theirX-ray emission in the infall regions of 23 massive (< M-200 > = 10(15) M-circle dot) clusters at 0.15 < z < 0.3. Highly complete spectroscopic coverage combined with 24 mu m imaging from Spitzer allows us to make a consistent and robust selection of cluster and group members including star-forming galaxies down to a stellar mass limit of M* = 2 x 10(10) M-circle dot. The fraction f(SF) of star-forming galaxies in infalling groups is lower and with a flatter trend with respect to clustercentric radius when compared to the rest of the cluster galaxy population. At R approximate to 1.3 r(200), the fraction of star-forming galaxies in infalling groups is half that in the cluster galaxy population. This is direct evidence that star-formation quenching is effective in galaxies already prior to them settling in the cluster potential, and that groups are favourable locations for this process.
  • A likely planet-induced gap in the disc around T Cha

    Hendler, Nathanial P; Pinilla, Paola; Pascucci, Ilaria; Pohl, Adriana; Mulders, Gijs; Henning, Thomas; Dong, Ruobing; Clarke, Cathie; Owen, James; Hollenbach, David; Univ Arizona, Lunar & Planetary Lab; Univ Arizona, Steward Observ, Dept Astron (OXFORD UNIV PRESS, 2018-03)
    We present high-resolution (0.11 x 0.06 arcsec(2)) 3mm ALMA observations of the highly inclined transition disc around the star T Cha. Our continuum image reveals multiple dust structures: an inner disc, a spatially resolved dust gap, and an outer ring. When fitting sky-brightness models to the real component of the 3mm visibilities, we infer that the inner emission is compact (<= 1 au in radius), the gap width is between 18 and 28 au, and the emission from the outer ring peaks at similar to 36 au. We compare our ALMA image with previously published 1.6 mu m VLT/SPHERE imagery. This comparison reveals that the location of the outer ring is wavelength dependent. More specifically, the peak emission of the 3mm ring is at a larger radial distance than that of the 1.6 mu m ring, suggesting that millimeter-sized grains in the outer disc are located farther away from the central star than micron-sized grains. We discuss different scenarios to explain our findings, including dead zones, star-driven photoevaporation, and planet-disc interactions. We find that the most likely origin of the dust gap is from an embedded planet, and estimate - for a single planet scenario - that TCha's gap is carved by a 1.2M(Jup) planet.
  • Search for pair production of up-type vector-like quarks and for four-top-quark events in final states with multiple b-jets with the ATLAS detector

    Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.; Abeloos, B.; Abidi, S. H.; AbouZeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Acharya, B. S.; Adachi, S.; Adamczyk, L.; Adelman, J.; Adersberger, M.; Adye, T.; Affolder, A. A.; Afik, Y.; Agheorghiesei, C.; Aguilar-Saavedra, J. A.; Ahmadov, F.; Aielli, G.; Akatsuka, S.; Åkesson, T. P. A.; Akilli, E.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albicocco, P.; Alconada Verzini, M. J.; Alderweireldt, S.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Ali, B.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allaire, C.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alshehri, A. A.; Alstaty, M. I.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amaral Coutinho, Y.; Ambroz, L.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amoroso, S.; Amrouche, C. S.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Angerami, A.; Anisenkov, A. V.; Annovi, A.; Antel, C.; Anthony, M. T.; Antonelli, M.; Antrim, D. J. A.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Araujo Ferraz, V.; Araujo Pereira, R.; Arce, A. T. H.; Ardell, R. E.; Arduh, F. A.; Arguin, J-F.; Argyropoulos, S.; Armbruster, A. J.; Armitage, L. J.; Arnaez, O.; Arnold, H.; Arratia, M.; Univ Arizona (SPRINGER, 2018-07-12)
    A search for pair production of up-type vector-like quarks (T) with a significant branching ratio into a top quark and either a Standard Model Higgs boson or a Z boson is presented. The same analysis is also used to search for four-top-quark production in several new physics scenarios. The search is based on a dataset of pp collisions at root s = 13TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb(-1). Data are analysed in the lepton+jets final state characterised by an isolated electron or muon with high transverse momentum large missing transverse momentum and multiple jets as well as the jets+E-T(miss) final state characterised by multiple jets and large missing transverse momentum. The search exploits the high multiplicity of jets identified as originating from b-quarks and the presence of boosted hadronically decaying top quarks and Higgs bosons reconstructed as large-radius jets characteristic of signal events. No significant excess above the Standard Model expectation is observed and 95% CL upper limits are set on the production cross sections for the different signal processes considered. These cross-section limits are used to derive lower limits on the mass of a vector-like T quark under several branching ratio hypotheses assuming contributions from T -> Wb Zt Ht decays. The 95% CL observed lower limits on the T quark mass range between 0.99TeV and 1.43TeV for all possible values of the branching ratios into the three decay modes considered significantly extending the reach beyond that of previous searches. Additionally upper limits on anomalous four-top-quark production are set in the context of an effective field theory model as well as in an universal extra dimensions model."
  • Search for exclusive Higgs and Z boson decays to ϕγ and ργ with the ATLAS detector

    Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.; Abeloos, B.; Abidi, S. H.; AbouZeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adachi, S.; Adamczyk, L.; Adelman, J.; Adersberger, M.; Adye, T.; Affolder, A. A.; Afik, Y.; Agatonovic-Jovin, T.; Agheorghiesei, C.; Aguilar-Saavedra, J. A.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akatsuka, S.; Akerstedt, H.; Åkesson, T. P. A.; Akilli, E.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albicocco, P.; Alconada Verzini, M. J.; Alderweireldt, S. C.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Ali, B.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alshehri, A. A.; Alstaty, M. I.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amoroso, S.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Angerami, A.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antel, C.; Antonelli, M.; Antonov, A.; Antrim, D. J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Araujo Ferraz, V.; Arce, A. T. H.; Ardell, R. E.; Arduh, F. A.; Arguin, J-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Armitage, L. J.; Univ Arizona (SPRINGER, 2018-07-19)
    A search for the exclusive decays of the Higgs and Z bosons to a phi or rho meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of up to 35.6 fb(-1) collected at root s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95% confidence level were obtained on the branching fractions of the Higgs boson decays to phi gamma and rho gamma of 4.8 x 10(-4) and 8.8 x 10(-4), respectively. The corresponding 95% confidence level upper limits for the Z boson decays are 0.9 x 10(-6) and 25 x 10(-6) for phi gamma and rho gamma, respectively.
  • Radar Sounding of Open Basin Lakes on Mars

    Shoemaker, E. S.; Baker, D. M. H.; Carter, L. M.; Univ Arizona, Lunar & Planetary Lab (AMER GEOPHYSICAL UNION, 2018-06)
    Orbital observations of the surface of Mars indicate that ancient basins were once host to lakes that may have been depocenters of sedimentary materials, including hydrated minerals like phyllosilicates. Later volcanic and sedimentary resurfacing may have developed a stratigraphy within the basins detectable through radar sounding data from the Shallow Radar instrument. Our radar survey of 61 open basin lakes (OBLs) revealed only one plausible reflector in a single basin east of Hellas Planitia. We investigated possible factors contributing to lack of radar detections in the other basins through detailed analysis of radargrams and subsurface characteristics of OBLs. As possible hosts to previous habitable environments, OBLs on Mars are important sites for future robotic and human missions. A full understanding of the factors influencing the radar signal, as addressed here, is important for more fully characterizing the subsurface structure and geology at these locations. Plain Language Summary Mars was once host to ancient lakes that can currently be observed as a topographic depression in the surface with channels where water is thought to have once flowed called an open basin lake. This flowing water transported sediments into the lake which was later covered by further sedimentary or volcanic deposits. The interface between layers of material in the subsurface can be detected from orbit using the Shallow Radar instrument. Our survey of 61 open basin lakes revealed only one detectable interface in a single basin lake. We investigate possible factors that could contribute to the lack of identified interfaces through detailed analyses of available radar images and surface characteristics of the open basin lakes. We develop a method to characterize the degree of noise (clutter) in the radar images created by large surface features (>100m) up to 25km away from the position of the ground track of the spacecraft. However, this alone cannot explain the lack of detected interfaces. A rough subsurface or interface may be more likely. Further modeling will be necessary to characterize the radar characteristics of these basins as many are landing site candidates for future missions searching for formerly habitable environments.
  • Episodes of Aqueous Flooding and Effusive Volcanism Associated With Hrad Vallis, Mars

    Hamilton, Christopher W.; Mouginis-Mark, Peter J.; Sori, Michael M.; Scheidt, Stephen P.; Bramson, Ali M.; Univ Arizona, Lunar & Planetary Lab (AMER GEOPHYSICAL UNION, 2018-06)
    Hrad Vallis is an Amazonian-age outflow channel located in the northwestern part of the Elysium Volcanic Province of Mars. The formation of Hrad Vallis may have been associated with catastrophic aqueous floods and volcanism, which makes determining its emplacement history important for constraining the planet's hydrological and thermal evolution during the Amazonian Period. Through geological mapping, geomorphologic analysis, and numerical simulations we assess whether Hrad Vallis formed in association with mudflows (i.e., lahars), effusive volcanism, or a combination of both processes. Among the three youngest flows in the region, the lower and upper flow units are inferred to be the products of catastrophic aqueous floods, whereas the middle unit is interpreted to be phoehoe-like lava flow formed through the process of inflation over the course of decades. The latter flow unit is similar to terrestrial lava-rise plateaus, but its emplacement may have involved interactions with surficial ice deposits, which affected the flow path and resulted in a range of lava-water interactions. We conclude that Hrad Vallis had a complex history involving episodes of both aqueous flooding and effusive volcanism and that the interactions between lava and ice in these regions may have generated ephemeral hydrothermal systems with potential astrobiological significance. Plain Language Summary Major outflow channels on Mars may have been carved by either catastrophic aqueous floods or turbulent lava flows. Addressing the ambiguous origin of these channels is therefore important for constraining the hydrological and volcanic history of the planet. This study focuses on Hrad Vallis, which is a geologically recent (Amazonian-age) outflow channel located within the Elysium Volcanic Province, through a combination of mapping and modeling. We find evidence for both aqueous flooding and effusive volcanism associated with this channel, indicating a complex hydrologic and geologic history. However, lava flows in this region are interpreted to be the products of phoehoe-like lava flow emplacement, similar to terrestrial lava flows on Earth in New Mexico and Hawaii, and not highly turbulent flows as previously suggested. The identification of similar to 50m thick phoehoe-like lava flows near Hrad Vallis implies a gradual formation process over the course of decades, and heat from these lava flows may have interacted with ground ice to produce meltwater and steam. Lava-water interactions on Mars are important because they could generate habitable environments for microbial organisms that have adapted for survival within hydrothermal systems.
  • MAVEN/IUVS Stellar Occultation Measurements of Mars Atmospheric Structure and Composition

    Gröller, H.; Montmessin, F.; Yelle, R. V.; Lefèvre, F.; Forget, F.; Schneider, N. M.; Koskinen, T. T.; Deighan, J.; Jain, S. K.; Univ Arizona, Lunar & Planetary Lab (AMER GEOPHYSICAL UNION, 2018-06)
    The Imaging UltraViolet Spectrograph (IUVS) instrument of the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has acquired data on Mars for more than one Martian year. During this time, beginning with March 2015, hundreds of stellar occultations have been observed, in 12 dedicated occultation campaigns, executed on average every 2 to 3months. The occultations cover the latitudes from 80 degrees S to 75 degrees N and the full range longitude and local times with relatively sparse sampling. From these measurements we retrieve CO2, O-2, and O-3 number densities as well as temperature profiles in the altitude range from 20 to 160km, covering 8 orders of magnitude in pressure from approximate to 2x10(1) to approximate to 4 x 10(-7)Pa. These data constrain the composition and thermal structure of the atmosphere. The O-2 mixing ratios retrieved during this study show a high variability from 1.5 x 10(-3) to 6 x 10(-3); however, the mean value seems to be constant with solar longitude. We detect ozone between 20 and 60km. In many profiles there is a well-defined peak between 30 and 40km with a maximum density of 1-2x10(9)cm(-3). Examination of the vertical temperature profiles reveals substantial disagreement with models, with observed temperatures both warmer and colder than predicted. Examination of the altitude profiles of density perturbations and their variation with longitude shows structured atmospheric perturbations at altitudes above 100km that are likely nonmigrating tides. These perturbations are dominated by zonal wave numbers 2 and 3 with amplitudes greater than 45%.
  • Multiple spectral channels in branchiopods. II. Role in light-dependent behavior and natural light environments

    Lessios, Nicolas; Rutowski, Ronald L.; Cohen, Jonathan H.; Univ Arizona, Dept Neurosci (COMPANY BIOLOGISTS LTD, 2018-05)
    Light is a primary environmental factor used by aquatic invertebrates for depth selection behavior. Many branchiopod crustaceans live in ephemeral aquatic habitats. All branchiopod crustaceans studied to date express four or more visual opsins in their compound eyes. We asked whether two branchiopods, Triops longicaudatus and Streptocephalus mackini, use multiple spectral channels to regulate their position in the water column. At the lowest intensities that elicited photonegative behavior, both species had broad spectral bandwidths, suggesting they use multiple spectral photoreceptor classes. Male S. mackini were more likely to maintain a vertical position 8.0-12.0 cm below the surface than females, independently of whether females were present. Male photopositive behavior at low intensity was restricted to a narrow bandwidth centered at 532 nm, suggesting a single photoreceptor class is used to maintain position above females. We compared ephemeral pools from two regions in Arizona and found that diffuse light attenuation coefficients were two orders of magnitude greater than the most heavily attenuating coastal waters. At less than 1 m of depth, pools were often dimmer than terrestrial habitats under starlight. Soil particle size distribution in each region affected spectral light environments, and behavioral responses of field-caught shrimp were adapted to the spectral properties of their region. The results suggest that branchiopods predominantly use luminance vision summed from multiple spectral photoreceptor classes for depth selection in dim, spectrally variable environments. The neuroanatomical basis for summation is described in a companion paper.

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