Now showing items 21-40 of 91083

    • Snowpack‐ and Soil Water Content‐Related Hydrologic Indices and Their Association With Radial Growth of Conifers in the Sierra Nevada, California

      Shamir, Eylon; Meko, Dave; Touchan, Ramzi; Lepley, Kai S.; Campbell, Rochelle; Kaliff, Rebecca N.; Georgakakos, Konstantine P.; Univ Arizona, Lab Tree Ring Res (AMER GEOPHYSICAL UNION, 2020-12-18)
      The utility of a high-resolution snow-hydrologic model to derive climatological indices that describe the variability in radial growth of four conifer species in two Sierra Nevada sites is presented herein. Nine annual indices associated with radial growth were developed to represent the winter dormancy, characteristics of the snowpack and soil water content, and the duration of the seasons. Site chronologies of earlywood (EW) and latewood (LW) ring widths were developed for mountain hemlock (Tsuga mertensiana), red fir (Abies magnifica), white fir (Abies concolor), and ponderosa pine (Pinus ponderosa) at two sites on leeward and windward slopes. The signal strength for annual climatological indices derived from model output was tested with correlation and regression, in combination with principal components analysis. Results show significant snow-related climate signal in the tree-ring data, with substantial differences between species and between EW and LW. Dependence on previous year's snow and soil moisture (a lagged response) were found for EW of hemlock and red fir. The primary EW-LW signal contrast for those species is a shift toward dependence on current-year moisture conditions for LW, especially for red fir. Lagged climate response was less evident for white fir and ponderosa pine. Regression of tree-ring series on principal components of climatological indices showed a stronger average signal in EW (R-2 = 0.48) than in LW (R-2 = 0.35). Differences in tree-ring hydrologic signal at the two sites are attributed to microclimate and contrasts in snow regime. Results attest to the hydrologic model usefulness for investigating temporal relationships between tree rings and local climate.
    • Dietary Modification and Breast Cancer Mortality: Long-Term Follow-Up of the Women's Health Initiative Randomized Trial

      Chlebowski, Rowan T; Aragaki, Aaron K; Anderson, Garnet L; Pan, Kathy; Neuhouser, Marian L; Manson, JoAnn E; Thomson, Cynthia A; Mossavar-Rahmani, Yasmin; Lane, Dorothy S; Johnson, Karen C; et al. (AMER SOC CLINICAL ONCOLOGY, 2020-02-07)
      During 8.5 years of dietary intervention, breast cancer incidence and deaths as a result of breast cancer were nonsignificantly lower in the intervention group, while deaths after breast cancer were statistically significantly lower both during intervention and through a 16.1-year (median) follow-up. Now, after a long-term, cumulative 19.6-year (median) follow-up, the significant reduction in deaths after breast cancer persists (359 [0.12%] v 652 [0.14%] deaths; hazard ratio [HR], 0.85; 95% CI, 0.74 to 0.96; P = .01), and a statistically significant reduction in deaths as a result of breast cancer (breast cancer followed by death attributed to the breast cancer) emerged (132 [0.037%, annualized risk] v 251 [0.047%] deaths, respectively; HR, 0.79; 95% CI, 0.64 to 0.97; P = .02).
    • Effect of bromhexine in hospitalized patients with COVID-19

      Tolouian, Ramin; Mulla, Zuber D; Jamaati, Hamidreza; Babamahmoodi, Abdolreza; Marjani, Majid; Eskandari, Raha; Dastan, Farzaneh; Renal Section, Southern Arizona VA Health Care System, University of Arizona (BMJ Publishing Group, 2021-03-15)
      Background: Bromhexine is a potent inhibitor of transmembrane serine protease 2 and appears to have an antiviral effect in controlling influenza and parainfluenza infection; however, its efficacy in COVID-19 is controversial. Methods: A group of hospitalized patients with confirmed COVID-19 pneumonia were randomized using 1:1 allocation to either standard treatment lopinavir/ritonavir and interferon beta-1a or bromhexine 8 mg four times a day in addition to standard therapy. The primary outcome was clinical improvement within 28 days, and the secondary outcome measures were time to hospital discharge, all-cause mortality, duration of mechanical ventilation, the temporal trend in 2019-nCoV reverse transcription-polymerase chain reaction positivity and the frequency of adverse drug events within 28 days from the start of medication. Results: A total of 111 patients were enrolled in this randomized clinical trial and data from 100 patients (48 patients in the treatment arm and 52 patients in the control arm) were analyzed. There was no significant difference in the primary outcome of this study, which was clinical improvement. There was no significant difference in the average time to hospital discharge between the two arms. There were also no differences observed in the mean intensive care unit stay, frequency of intermittent mandatory ventilation, duration of supplemental oxygenation or risk of death by day 28 noted between the two arms. Conclusion: Bromhexine is not an effective treatment for hospitalized patients with COVID-19. The potential prevention benefits of bromhexine in asymptomatic postexposure or with mild infection managed in the community remain to be determined.
    • Optomechanical lasers for inertial sensing

      Wisniewski, Hayden; Richardson, Logan; Hines, Adam; Laurain, Alexandre; Guzmán, Felipe; Univ Arizona, James C Wyant Coll Opt Sci (OPTICAL SOC AMER, 2020-08-12)
      We have developed an inertially sensitive optomechanical laser by combining a vertical-external-cavity surface-emitting laser (VECSEL) with a monolithic fused silica resonator. By placing the external cavity mirror of the VECSEL onto the optomechanical resonator test mass, we create a sensor where external accelerations are directly transcribed onto the lasing frequency. We developed a proof-of-principle laboratory prototype and observe test mass oscillations at the resonance frequency of the sensor through the VECSEL lasing frequency, 4.18 +/- 0.03 Hz. In addition, we set up an ancillary heterodyne interferometer to track the motion of the mechanical oscillator's test mass, observing a resonance of 4.194 +/- 0.004 Hz. The interferometer measurements validate the VECSEL results, confirming the feasibility of using optomechanical lasers for inertial sensing. (C) 2020 Optical Society of America
    • A low-cost computational approach to analyze spiking activity in cockroach sensory neurons

      Torres, David J; Romero, Andres; Colgan, Wes; Ricoy, Ulises M; Department of Neuroscience, The University of Arizona (American Physiological Society, 2021-03-04)
      Undergraduates use a spike sorting routine developed in Octave to analyze the spiking activity generated from mechanical stimulation of spines of cockroach legs with the inexpensive SpikerBox amplifier and the free software Audacity. Students learn the procedures involved in handling the cockroaches and recording extracellular action potentials (spikes) with the SpikerBox apparatus as well as the importance of spike sorting for analysis in neuroscience. The spike sorting process requires students to choose the spike threshold and spike selection criteria and interact with the clustering process that forms the groups of similar spikes. Once the spike groups are identified, interspike intervals and neuron firing frequencies can be calculated and analyzed. A classic neurophysiology lab exercise is thus adapted to be interdisciplinary for underrepresented students in a small rural college. © 2021 the American Physiological Society. All Rights Reserved
    • Pulmonary infection secondary to Blastobotrys raffinosifermentans in a cystic fibrosis patient: Review of the literature

      Al-Obaidi, Mohanad; Badali, Hamid; Cañete-Gibas, Connie; Patterson, Hoja P; Wiederhold, Nathan P; University of Arizona (Wiley Blackwell, 2021-02-08)
      Background: The genus Blastobotrys consists of at least 20 species. Disease in humans has been reported with B adeninivorans, B raffinosifermentans, B proliferans and B serpentis, mostly in immunocompromised patients and those with cystic fibrosis. Objective: We report a lung infection secondary to B raffinosifermentans in a cystic fibrosis patient successfully treated with isavuconazole and review the literature of invasive infections caused this genus. We also evaluated clinical isolates in our laboratory for species identification and antifungal susceptibility. Methods: Phylogenetic analysis was performed on a collection of 22 Blastobotrys isolates in our reference laboratory, and antifungal susceptibility patterns were determined for nine clinically available antifungals against 19 of these isolates. Results: By phylogenetic analysis, 21 of the 22 isolates in our collection were identified as B raffinosifermentans and only 1 as B adeninivorans. Most were cultured from the respiratory tract, although others were recovered from other sources, including CSF and blood. Isavuconazole, caspofungin and micafungin demonstrated the most potent in vitro activity, followed by amphotericin B. In contrast, fluconazole demonstrated poor activity. The patient in this case responded to isavuconazole treatment for breakthrough infection due to B raffinosifermentans that was cultured from pleural fluid while on posaconazole prophylaxis post–bilateral lung transplantation for cystic fibrosis. Conclusions: Blastobotrys species are rare causes of infections in humans and primarily occur in immunocompromised hosts. In our collection, the majority of isolates were identified as B raffinosifermentans. To our knowledge, this is the first report of successful treatment of such an infection with isavuconazole. © 2021 Wiley-VCH GmbH
    • Use of Crotalidae equine immune F(ab’)2 antivenom for treatment of an Agkistrodon envenomation

      Wilson, B. Z.; Larsen, J.; Smelski, G.; Dudley, S.; Shirazi, F. M.; Arizona Poison and Drug Information Center, University of Arizona (Taylor and Francis Ltd., 2021-03-11)
      Introduction: Anavip (F(ab’)2AV) is a lyophilized F(ab’)2 immunoglobulin fragment derived from horses immunized with venom from Bothrops asper and Crotalus durissus. It was approved by the FDA in 2015 for treatment of North American rattlesnake envenomation but not for Agkistrodon envenomation. Published data regarding the efficacy and safety of Anavip in treating Agkistrodon envenomations is limited. We present a case of a patient treated with Anavip after confirmed Agkistrodon laticinctus envenomation. Case details: A 77 year-old man was bitten on his fifth finger by a captive A. laticinctus. He was taken to a local emergency department where he received a 10 vial initial dose of F(ab’)2AV for pain and swelling and was transferred. At the receiving facility, his pain had improved and his swelling had not progressed. Over the next 30 h, his platelets declined to 132,000/mm3 and he received an additional 4 vials of F(ab’)2AV. The remainder of his course was unremarkable with complete recovery by 3 months. Discussion: This case provides an additional published datapoint on the use of this F(ab’)2AV in the treatment of envenomation by Agkistrodon. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
    • Integration of metabolomics and transcriptomics reveals convergent pathways driving radiation-induced salivary gland dysfunction

      Meeks, Lauren; De Oliveira Pessoa, Diogo; Martinez, Jessica A; Limesand, Kirsten H; Padi, Megha; Department of Nutritional Sciences, University of Arizona; Bioinformatics Shared Resource, Arizona Cancer Center, University of Arizona; University of Arizona Cancer Center; Department of Molecular and Cellular Biology, University of Arizona (American Physiological Society, 2021-03-15)
      Radiation therapy for head and neck cancer causes damage to the surrounding salivary glands, resulting in salivary gland hypofunction and xerostomia. Current treatments do not provide lasting restoration of salivary gland function following radiation; therefore, a new mechanistic understanding of the radiation-induced damage response is necessary for identifying therapeutic targets. The purpose of the present study was to investigate the metabolic phenotype of radiation-induced damage in parotid salivary glands by integrating transcriptomic and metabolomic data. Integrated data were then analyzed to identify significant gene-metabolite interactions. Mice received a single 5 Gy dose of targeted head and neck radiation. Parotid tissue samples were collected 5 days following treatment for RNA sequencing and metabolomics analysis. Altered metabolites and transcripts significantly converged on a specific region in the metabolic reaction network. Both integrative pathway enrichment using rank-based statistics and network analysis highlighted significantly coordinated changes in glutathione metabolism, energy metabolism (TCA cycle and thermogenesis), peroxisomal lipid metabolism, and bile acid production with radiation. Integrated changes observed in energy metabolism suggest that radiation induces a mitochondrial dysfunction phenotype. These findings validated previous pathways involved in the radiation-damage response, such as altered energy metabolism, and identified robust signatures in salivary glands, such as reduced glutathione metabolism, that may be driving salivary gland dysfunction.
    • Neighborhood Context and Juvenile Recidivism: A Spatial Analysis of Organizations and Reoffending Risk

      Thompson-Dyck, Kendra; Univesity of Arizona (SAGE Publications Inc., 2021-03-14)
      Leveraging point-level spatial data from the Phoenix area, we consider the role of nearby organizations as contextual factors that amplify or reduce reoffending risk among juvenile offenders after court completion. Using survival models, we examine whether residential proximity to seven types of organizations impacts risk of recidivism, net of neighborhood disadvantage and offender characteristics. Aggregate neighborhood disadvantage was not associated with reoffending risk and organizational findings were mixed. Low-level offenders with more total organizations nearby had a higher risk of new property offenses, while the risk of drug and violent reoffending nearly doubled for diversion youth residing near police facilities or detention centers. Individual demographics and prior offense histories remained the strongest, most consistent predictors of juvenile recidivism.
    • Facilitated Communication, Neurodiversity, and Human Rights

      Simmons, William Paul; Boynton, Janyce; Landman, Todd; University of Arizona (Johns Hopkins University Press, 2021-02-28)
      Facilitated Communication (FC) has rightly been labeled a pseudoscience as there are no controlled studies showing its validity as a form of communication for people with severe autism or other disabilities. In controlled studies, it has been the facilitator and not the person with disabilities that is generating the communication. Spurious communications have led to numerous cases of sexual assault and false accusations of misconduct. Nev-ertheless, FC remains widely practiced and touted even by supposed experts. We argue that this controversy has important human rights implications, especially for activists attempting to amplify marginalized people’s voices by speaking for them, and raises critical questions about epistemological issues in human rights work. © 2021 by Johns Hopkins University Press.
    • AMS 14C Dating of the Mayan Codex of Mexico Revisited

      Solís, Corina; Martínez Carrillo, Miguel Á; Rodríguez-Ceja, María; Chávez, Efraín; Christen, J Andrés; Jull, A J Timothy; Department of Geosciences, University of Arizona; University of Arizona AMS Laboratory (Cambridge University Press (CUP), 2020-09-01)
      The Mayan Codex of Mexico (MCM), the only Mayan codex found in the 20th century, was unveiled in 1971 during the Ancient Maya Calligraphy exhibition at Club Grolier. The codex comprises 10 pages of bark paper in accordion format, coated with a layer of plaster on both sides. It illustrates the synodic cycles of Venus, with its four phases. Since its discovery, the MCM has been subject to controversy and discussions about its authenticity. In 2016, a group of specialists led by Baltazar Brito chief of the National Library of Anthropology and History, carried out an exhaustive study of the codex with the purpose of determining its temporality and authenticity. In this work, the pre-Columbian authenticity of the codex is verified by the radiocarbon (14C) technique using AMS. Two cleaning procedures were contrasted: the standard acid-base-acid (ABA) protocol and a second one with Soxhlet plus ABA. Results obtained when samples were prepared following ABA protocol only, placed the age of the bark paper between 991 and 1147 cal AD. The second cleaning method with Soxhlet plus ABA, resulted in younger ages, between 1159 and 1261 cal AD. However, we consider that when Sohxlet is used as part of the cleaning protocol, organic contaminants are reduced to a minimum, and 14C dates are more reliable. These results indicate that the vegetal support of the MCM belongs to Postclassical Mayan period and place it as the oldest known manuscript of America found to date.
    • Methane, Monsoons, and Modulation of Millennial‐Scale Climate

      Thirumalai, Kaustubh; Clemens, Steven C.; Partin, Judson W.; Univ Arizona, Dept Geosci (AMER GEOPHYSICAL UNION, 2020-04-23)
      Earth's orbital geometry exerts a profound influence on climate by regulating changes in incoming solar radiation. Superimposed on orbitally paced climate change, Pleistocene records reveal substantial millennial-scale variability characterized by abrupt changes and rapid swings. However, the extent to which orbital forcing modulates the amplitude and timing of these millennial variations is unclear. Here we isolate the magnitude of millennial-scale variability (MMV) in two well-dated records, both linked to precession cycles (19,000- and 23,000-year periodicity): composite Chinese speleothem delta O-18, commonly interpreted as a proxy for Asian monsoon intensity, and atmospheric methane. At the millennial timescale (1,000-10,000 years), we find a fundamental decoupling wherein precession directly modulates the MMV of methane but not that of speleothem delta O-18, which is shown to be strikingly similar to the MMV of Antarctic ice core delta H-2. One explanation is that the MMV of methane responds to changes in midlatitude to high-latitude insolation, whereas speleothem delta O-18 is modulated by internal climate feedbacks.
    • Relative Timing of Nightside and Dayside Plasmapause Motion: Two Events in June 2001

      Goldstein, J.; Sandel, B. R.; Univ Arizona, Lunar & Planetary Lab (AMER GEOPHYSICAL UNION, 2019-12-22)
      We examine the relative timing of dayside and nightside plasmapause motion following southward interplanetary magnetic field turnings on 2 and 9 June 2001. For both events the delay between the dayside and nightside plasmapause response is less than the temporal resolution of Imager for Magnetopause-to-Aurora Global Exploration extreme ultraviolet observations (10 min). Our result thus establishes a possible upper limit (<= 10 min) on the day-to-night onset delay. From analysis of the extreme ultraviolet-observed plasmapause motion we find on 2 June the time-averaged plasmapause E field was (in mV/m) 0.61 near noon magnetic local time, 0.35 near midnight magnetic local time, and 0.44 overall. The normalized plasmapause speed data (both dayside and nightside) are fitted to the curve (0.09 +/- 0.05)L-3, consistent with a spatially uniform and time-constant dawn-dusk penetration E field that is 9% of the solar wind field. On 9 June the time-averaged E field values (mV/m) were 0.24 (dayside), 0.28 (nightside), and 0.26 (overall); the plasmapause motion was consistent with a penetration E field 10% of the solar wind field. Plasmasphere erosion is a fundamental element of the dynamic magnetospheric response to solar wind driving. This study yields an important observational constraint on the day-to-night timing of the plasmapause response. The result also has implications for the two main models for the cause of erosion (convection and interchange).
    • Greenland Ice Sheet Contribution to 21st Century Sea Level Rise as Simulated by the Coupled CESM2.1‐CISM2.1

      Muntjewerf, Laura; Petrini, Michele; Vizcaino, Miren; Ernani da Silva, Carolina; Sellevold, Raymond; Scherrenberg, Meike D. W.; Thayer‐Calder, Katherine; Bradley, Sarah L.; Lenaerts, Jan T. M.; Lipscomb, William H.; et al. (AMER GEOPHYSICAL UNION, 2020-04-09)
      The Greenland Ice Sheet (GrIS) mass balance is examined with an Earth system/ice sheet model that interactively couples the GrIS to the broader Earth system. The simulation runs from 1850 to 2100, with historical and SSP5-8.5 forcing. By the mid-21st century, the cumulative GrIS contribution to global mean sea level rise (SLR) is 23 mm. During the second half of the 21st century, the surface mass balance becomes negative in all drainage basins, with an additional SLR contribution of 86 mm. The annual mean GrIS mass loss in the last two decades is 2.7-mm sea level equivalent (SLE) year(-1). The increased SLR contribution from the surface mass balance (3.1 mm SLE year(-1)) is partly offset by reduced ice discharge from thinning and retreat of outlet glaciers. The southern GrIS drainage basins contribute 73% of the mass loss in mid-century but 55% by 2100, as surface runoff increases in the northern basins.
    • Blinding multiprobe cosmological experiments

      Muir, J; Bernstein, G M; Huterer, D; Elsner, F; Krause, E; Roodman, A; Allam, S; Annis, J; Avila, S; Bechtol, K; et al. (OXFORD UNIV PRESS, 2020-04-15)
      The goal of blinding is to hide an experiment's critical results - here the inferred cosmological parameters - until all decisions affecting its analysis have been finalized. This is especially important in the current era of precision cosmology, when the results of any new experiment are closely scrutinized for consistency or tension with previous results. In analyses that combine multiple observational probes, like the combination of galaxy clustering and weak lensing in the Dark Energy Survey (DES), it is challenging to blind the results while retaining the ability to check for (in)consistency between different parts of the data. We propose a simple new blinding transformation, which works by modifying the summary statistics that are input to parameter estimation, such as two-point correlation functions. The transformation shifts the measured statistics to new values that are consistent with (blindly) shifted cosmological parameters while preserving internal (in)consistency. We apply the blinding transformation to simulated data for the projected DES Year 3 galaxy clustering and weak lensing analysis, demonstrating that practical blinding is achieved without significant perturbation of internal-consistency checks, as measured here by degradation of the chi(2) between the data and best-fitting model. Our blinding method's performance is expected to improve as experiments evolve to higher precision and accuracy.
    • RELICS: spectroscopy of gravitationally lensed z ≃ 2 reionization-era analogues and implications for C iii] detections at z > 6

      Mainali, Ramesh; Stark, Daniel P; Tang, Mengtao; Chevallard, Jacopo; Charlot, Stéphane; Sharon, Keren; Coe, Dan; Salmon, Brett; Bradley, Larry D; Johnson, Traci L; et al. (OXFORD UNIV PRESS, 2020-03-20)
      Recent observations have revealed the presence of strong C III] emission (EWC III] > 20 angstrom) in z > 6 galaxies, the origin of which remains unclear. In an effort to understand the nature of these line emitters, we have initiated a survey targeting C III] emission in gravitationally lensed reionization-era analogues identified in Hubble Space Telescope imaging of clusters itom the Reionization Lensing Cluster Survey. Here, we report initial results on four galaxies selected to have low stellar masses (2-8 x 10(7) M-circle dot) and J(125)-band flux excesses indicative of intense [O III] H beta emission (EW[O III] (+)(H beta) = 500-2000 angstrom), similar to what has been observed at z > 6. We detect C III] emission in three of the four sources, with the C III] EW reaching values seen in the reionization era (EWC III] 17-22 angstrom) in the two sources with the strongest optical line emission (EW[O III]+H beta 2000 angstrom). We have obtained a Magellan/FIRE (Folded-port InfraRed Echellette) near-infrared spectrum of the strongest C III] emitter in our sample, revealing gas that is both metal poor and highly ionized. Using photoionization models, we are able to simultaneously reproduce the intense C III] and optical line emission for extremely young (2-3 Myr) and metal-poor (0.06-0.08 Z(circle dot)) stellar populations, as would be expected after a substantial upturn in the star formation rate of a low-mass galaxy. The sources in this survey are among the first for which C III] has been used as the primary means of redshift confirmation. We suggest that it should be possible to extend this approach to z > 6 with current facilities, using C III] to measure redshifts of objects with IRAC excesses indicating EW[O III]+H beta 2000 angstrom, providing a method of spectroscopic confirmation independent of Ly alpha.
    • Isotopologues of dense gas tracers in nearby infrared bright galaxies

      Li, Fei; Wang, Junzhi; Fang, Min; Li, Shanghuo; Zhang, Zhi-Yu; Gao, Yu; Kong, Minzhi; Univ Arizona, Dept Astron (OXFORD UNIV PRESS, 2020-03-13)
      We present 1 and 3 mm observations of the C-13- and N-15-bearing isotopologues of dense gas tracers towards eight nearby infrared-bright galaxies. With the Institut de Radioastronomie Millimetrique 30-m telescope, we observed the J = 1-0 transitions of (HCN)-C-13, (HCN)-N-15, (HCO+)-C-13 , (HNC)-C-13, and (HNC)-N-15 towards M 82, NGC 3079, IC 694, Mrk 231, and NGC 6240. The J = 3-2 transition of (HCN)-C-13 was obtained in M 82, NGC 3079, NGC 3504, NGC 4418, NGC 6240, and NGC 6946, using the 10-m Submillimeter Telescope (SMT). We report the first detections of (HNC)-C-13 J = 1-0 and (HCN)-C-13 J = 3-2 in M 82, and (HCN)-C-13 J = 3-2 in NGC 6240 and NGC 3079. We find different line profiles between the J = 1-0 and 3-2 transitions of (HCN)-C-13 in both M 82 and NGC 3079. The optical depths of HCN show significant variations among the sample, indicating that dense gas masses estimated from the line luminosities of HCN J = 1-0 and 3-2 should be treated with caution for individual galaxies. Optical depth of HCN J = 3-2 is found to be higher than that of HCN J = 1-0 in M 82, NGC 3079, NGC 4418, and NGC 6240, which indicates that ground state transitions of dense gas tracers might better trace the star-forming gas than the high-J transitions. Based on the (HCN)-C-13/(HCN)-N-15 line ratios, with the double-isotopic method, low N-14/N-15 abundance ratios of 120 and 140 are found in NGC 3079 and Mrk 231, respectively.
    • The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

      Lemon, C; Auger, M W; McMahon, R; Anguita, T; Apostolovski, Y; Chen, G C-F; Fassnacht, C D; Melo, A D; Motta, V; Shajib, A; et al. (OXFORD UNIV PRESS, 2020-03-09)
      We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345 -2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053 -2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near In fraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar + star pairs from DES data using parametric multiband modelling, and compare variability in each system's components. By measuring the reduced chi(2) associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.
    • Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio

      Verscharen, Daniel; Parashar, Tulasi N; Gary, S Peter; Klein, Kristopher G; Univ Arizona, Lunar & Planetary Lab; Univ Arizona, Dept Planetary Sci (OXFORD UNIV PRESS, 2020-04-13)
      The magnetization vertical bar Omega(e)vertical bar/omega(e) is an important parameter in plasma astrophysics, where Omega(e) and omega(e) are the electron gyro-frequency and electron plasma frequency, respectively. It depends only on the mass ratio m(i)/m(e) and the light-to-Alfven speed ratio c/v(Ai), where in, (m(e)) is the ion (electron) mass, c is the speed of light, and v(Ai) is the ion Alfven speed. Non-linear numerical plasma models such as particle-in-cell simulations must often assume unrealistic values for mike and for c/v(Ai). Because linear theory yields exact results for parametric scalings of wave properties at small amplitudes, we use linear theory to investigate the dispersion relations of Alfven/ion-cyclotron and fast-magnetosonic/whistler waves as prime examples for collective plasma behaviour depending on m(i)/m(e) and c/v(Ai). We analyse their dependence on m(i)/m(e) and c/v(Ai) in quasi-parallel and quasi-perpendicular directions of propagation with respect to the background magnetic field for a plasma with beta(j) similar to 1, where beta(j) is the ratio of the thermal to magnetic pressure for species j. Although their dispersion relations are largely independent of c/v(Ai) for c/v(Ai) greater than or similar to 10, the mass ratio mime has a strong effect at scales smaller than the ion inertial length. Moreover, we study the impact of relativistic electron effects on the dispersion relations. Based on our results, we recommend aiming for a more realistic value of m(i)/m(e) than for a more realistic value of c/v(Ai) in non-relativistic plasma simulations if such a choice is necessary, although relativistic and sub-Debye-length effects may require an additional adjustment of c/v(Ai).
    • Linear and Nonlinear Ultrasonic Techniques for Monitoring Stress-Induced Damages in Concrete

      Castellano, Anna; Fraddosio, Aguinaldo; Piccioni, Mario Daniele; Kundu, Tribikram; Department of Materials Science and Engineering, University of Arizona; Department of Civil and Architectural Engineering and Mechanics, University of Arizona; Department of Aerospace and Mechanical Engineering, University of Arizona (ASME International, 2021-03-24)
      When stress in concrete exceeds certain threshold value, microcracks are nucleated, these microcracks can propagate and coalesce forming macrocracks, resulting in the gradual decay of the mechanical properties of concrete and eventual failure of the concrete structures. For safety concerns, one needs to develop suitable nondestructive testing methods capable of detecting past overloads of concrete structures during its service life. In this work, the stress-induced damage in concrete is monitored using ultrasonic techniques, exploiting the coupling between the stress level experienced by concrete and its wave propagation parameters. Cyclic compression tests with increasing maximum load level have been performed on specimens made of concrete with coarse-grained (CG) aggregates. Experimental results have been analyzed by two different ultrasonic methods—the linear and the nonlinear ultrasonic techniques. In linear ultrasonic technique, the stress level experienced by the specimens is related to the variations in signal amplitude and velocity of ultrasonic waves. In nonlinear ultrasonic method, the sideband peak count (SPC) technique is used for revealing the stress-induced damage corresponding to each load step. In comparison to linear ultrasonic parameters, the nonlinear ultrasonic parameter SPC-I appears to be more sensitive to the variations of the internal material structures during both loading and unloading phases. Moreover, the SPC technique has shown to be capable of identifying both the initial damage due to the evolution and nucleation of microcracks at the microscopic scale, and the subsequent damages induced by high overload, resulting in an irreversible degradation of the mechanical properties.