Now showing items 10487-10506 of 11151

    • Truth and Genre in Pindar

      Park, Arum; University of Arizona (Cambridge University Press, 2013-05)
      By convention epinician poetry claims to be both obligatory and truthful, yet in the intersection of obligation and truth lies a seeming paradox: the poet presents his poetry as commissioned by a patron but also claims to be unbiased enough to convey the truth. In Slater's interpretation Pindar reconciles this paradox by casting his relationship to the patron as one of guest-friendship: when he declares himself a guest-friend of the victor, he agrees to the obligation ‘a) not to be envious of his xenos and b) to speak well of him. The argumentation is: Xenia excludes envy, I am a xenos, therefore I am not envious and consequently praise honestly’. Slater observes that envy may foster bias against the patron, but the problem of pro-patron bias remains: does the poet's friendship with and obligation to his patron produce praise at the expense of truth?
    • Truth-aware Optimal Decision-making Framework with Driver Preferences for V2V Communications

      Sun, Mingshun; Li, Ming; Gerdes, Ryan; Univ Arizona, Dept ECE (IEEE, 2018-08-13)
      In Vehicle-to-Vehicle (V2V) communications, malicious actors may spread false information to undermine the safety and efficiency of the vehicular traffic stream. Thus, vehicles must determine how to respond to the contents of messages which maybe false even though they are authenticated in the sense that receivers can verify contents were not tampered with and originated from a verifiable transmitter. Existing solutions to find appropriate actions are inadequate since they separately address trust and decision, require the honest majority (more honest ones than malicious), and do not incorporate driver preferences in the decision-making process. In this work, we propose a novel trust-aware decision-making framework without requiring an honest majority. It securely determines the likelihood of reported road events despite the presence of false data, and consequently provides the optimal decision for the vehicles. The basic idea of our framework is to leverage the implied effect of the road event to verify the consistency between each vehicle's reported data and actual behavior, and determine the data trustworthiness and event belief by integrating the Bayes' rule and Dempster Shafer Theory. The resulting belief serves as inputs to a utility maximization framework focusing on both safety and efficiency. This framework considers the two basic necessities of the Intelligent Transportation System and also incorporates drivers' preferences to decide the optimal action. Simulation results show the robustness of our framework under the multiple-vehicle attack, and different balances between safety and efficiency can be achieved via selecting appropriate human preference factors based on the driver's risk-taking willingness.
    • Try-It-On: Preparing family nurse practitioners to use holistic integrative interventions to reduce opioid prescriptions in chronic pain management

      Gregg, S Renee; Brown, Angela; Pasvogel, Alice; Univ Arizona, Coll Nursing (LIPPINCOTT WILLIAMS & WILKINS, 2020-01)
      In the United States, more than 130 people die each day from an opioid overdose. Nonopioid chronic pain management options are necessary in primary care. This educational innovation describes a new curriculum to teach future family nurse practitioner (FNP) prescribers holistic integrative interventions to decrease overprescribing of opioids for chronic pain management. The Modeling and Role Modeling theory and Kirkpatrick Evaluation Model guided the development and implementation of the curriculum innovation using a Try-It-On teaching-learning strategy, which focuses on immersion experience. The focus was to teach students to communicate effectively with patients in an effort to increase patient awareness of the pathophysiology of pain, risks of opioid use, and holistic integrative pain management options. Students learned to manage chronic pain within a holistic focus through immersion within integrative modalities, such as yoga, meditation, mindfulness, and guided imagery. Pre and post participation evaluations documented students' increased comfort level managing patients with chronic pain. Students reported they were much more likely to prescribe holistic integrative modalities after completing the Try-It-On learning modules. Holistic integrative interventions are a viable treatment option and/or adjunct treatment for chronic pain management. In conclusion, using the Try-It-On, teaching-learning strategy provided FNP students with the tools needed to prescribe nonopioid holistic integrative interventions to manage chronic pain.
    • TSPEC4: Near-IR spectroscopy for the SOAR telescope

      Herter, T.; Henderson, C.; Bonati, M.; Wilson, J.; Allers, K.; David, N.; Elias, J.; James, D.; Piraces, J.; Points, S.; et al. (SPIE, 2020)
      We describe the design and implementation of a fourth version of the TripleSpec near-infrared spectrograph (TSpec4). This version of the instrument was designed for and first implemented on the 4-m Blanco telescope on Cerro Tololo, and subsequently converted for use on the 4-m Southern Astrophysical Research (SOAR) Telescope on Cerro Pachon. Details of the changed opto-mechanical design and mounting arrangements are discussed. An updated data pipeline provides reduced spectra from the instrument. We describe the required modifications and the performance of both implementations of TSpec4. The move from the Blanco to SOAR required changing from operation at a classical Cassegrain f/8 focus to operation at a Nasmyth f/16 focus. The SOAR mount also employs a rotator and required accommodation to a significantly different back-focal distance inside the instrument. These changes were implemented by modifying the instrument fore-optics which feeds light onto the slit at f/10.6. The spectrograph and slit viewer optics are unchanged. A dichroic reflects infrared light toward the instrument while passing visible light to a SOAR facility guider; this removes the shortest wavelengths from the spectra and in turn required modification of the data reduction pipeline. As the telescopes have similar apertures, the performance of the instrument is similar on both, though on SOAR image quality is somewhat better and details of the instrument's optical properties differ also. Flexure performance differs as well due to the different instrument locations. © 2020 SPIE
    • Tsuji-Trost Cyclization of Disulfonamides: Synthesis of 12-Membered, 11-Membered, and Pyridine-Fused Macrocyclic Triamines

      Ali, Rameez; Anugu, Sreenivasa; Chawla, Reena; Demillo, Violeta G; Goulinet-Mateo, Florian; Gyawali, Sagar; Hamal, Sunil; Jones, Dylan E; Lamprecht, Katrin; Le, Truc; et al. (AMER CHEMICAL SOC, 2019-01-31)
      Macrocyclic triamine disulfonamides can be synthesized by double Tsuji-Trost N-allylation reaction of open-chain disulfonamides with 2-alkylidene-1,3-propanediyl bis(carbonates). The previously used Atkins-Richman macrocyclization method generally gives lower yields and requires more tedious purification of the product. Solvent, palladium source, ligand, and concentration have all been varied to optimize the yields of two key 12-membered ring bioactive compounds, CADA and VGD020. The new approach tolerates a wide range of functional groups and gives highest yields for symmetrical compounds in which the acidities of the two sulfonamide groups are matched, although the yields of unsymmetrical compounds are still generally good. The method has also been extended to the synthesis of 11-membered rings, pyridine-fused macrocycles, and products bearing an ester or aryl substituent on the exocyclic double bond.
    • Tsunami waves extensively resurfaced the shorelines of an early Martian ocean

      Rodriguez, J. Alexis P.; Fairén, Alberto G.; Tanaka, Kenneth L.; Zarroca, Mario; Linares, Rogelio; Platz, Thomas; Komatsu, Goro; Miyamoto, Hideaki; Kargel, Jeffrey S.; Yan, Jianguo; et al. (NATURE PUBLISHING GROUP, 2016-05-19)
      It has been proposed that similar to 3.4 billion years ago an ocean fed by enormous catastrophic floods covered most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in the circum-Chryse and northwestern Arabia Terra regions of the northern plains, in combination with numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide impacts, resulting in craters similar to 30 km in diameter and occurring perhaps a few million years apart. The tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes, which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces. The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement took place following a transition into a colder global climatic regime that occurred after the older tsunami event. We conclude that, on early Mars, tsunamis played a major role in generating and resurfacing coastal terrains.
    • Tuberculosis Treatment Completion in a United States/Mexico Binational Context

      Valencia, Celina I.; Ernst, Kacey; Rosales, Cecilia Ballesteros; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Dept Commun Environm & Policy; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Dept Epidemiol & Biostatist; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Div Publ Hlth Practice & Translat Res (FRONTIERS MEDIA SA, 2017-05-24)
      Background: Tuberculosis (TB) remains a salient public health issue along the U.S./Mexico border. This study seeks to identify the social and structural factors, which are associated with TB disease burden in the binational geographic region. Identification of barriers of treatment completion provides the necessary framework for developing evidence-based interventions that are culturally relevant and context specific for the U.S./Mexico border region. Methods: Retrospective study of data extracted from medical charts (n = 439) from Yuma County Health Department (YCHD) (n = 160) and Centro de Salud San Luis Rio Colorado (n = 279). Patients currently accessing TB treatment at either facility were excluded from the study. Chi-square, unadjusted odds ratios, and logistic regression were utilized to identify characteristics associated with successful TB treatment in this population. Findings: The study population was predominantly male (n = 327). Females were more likely to complete TB treatment (OR = 3.71). The absence of drug use and/or the absence of an HIV positive diagnosis were found to be predictors of TB treatment completion across both clinical sites. Forty-four percent (43.59%) (n = 85) TB patients treated at CDS San Luis did not complete treatment versus 40.35% (n = 49) of TB patients who did not complete treatment at YCHD. Moving from the area or being deported was the highest category (20.78%) for incomplete TB treatment in the population (n = 64) across both clinical sites.
    • Tumor biopsy and patient enrollment in clinical trials for advanced hepatocellular carcinoma

      Rimassa, Lorenza; Reig, Maria; Abbadessa, Giovanni; Peck-Radosavljevic, Markus; Harris, William; Zagonel, Vittorina; Pastorelli, Davide; Rota Caremoli, Elena; Porta, Camillo; Damjanov, Nevena; et al. (BAISHIDENG PUBLISHING GROUP INC, 2017)
      Tumor biopsies may help to reliably distinguish hepatocellular carcinoma (HCC) from other tumors, mostly cholangiocarcinoma as well as to identify the patient populations who most benefit from target-driven HCC treatments, in order to improve the success rate of experimental therapies. Clarifying tumor biology may also lead to identify biomarkers with prognostic role and/or enabling to predict response or resistance to therapies. Recently, clinical trials have more efficiently included biomarker endpoints and increasingly collected tumor tissue from enrolled patients. Due to their frail status and sometimes fast-progressing disease, the performance status of patients with HCC progressing on first-line therapy can deteriorate quickly, preventing their enrollment in clinical trials. However, the challenge of identifying the proper patient at the proper time can be overcome by periodic inter-department meetings involving the key specialists taking care of HCC patients, and solid networks between research centers and referring institutions. An early planned biopsy would also facilitate timely inclusion of patients in biology-driven clinical trials. Ultimately, institution of multidisciplinary teams can optimize treatment choice, biopsy timing, and quick enrollment of patients in clinical trials, before their performance status deteriorates.
    • Tumor suppressor ING4 inhibits estrogen receptor activity in breast cancer cells

      Keenen, Madeline; Kim, Suwon; Univ Arizona, Coll Med, Dept Basic Med Sci (DOVE MEDICAL PRESS LTD, 2016-11)
      Resistance to antiestrogen therapy remains a significant problem in breast cancer. Low expression of inhibitor of growth 4 (ING4) in primary tumors has been correlated with increased rates of recurrence in estrogen receptor-positive (ER+) breast cancer patients, suggesting a role for ING4 in ER signaling. This study provides evidence that ING4 inhibits ER activity. ING4 overexpression increased the sensitivity of T47D and MCF7 ER+ breast cancer cells to hormone deprivation. ING4 attenuated maximal estrogen-dependent cell growth without affecting the dose-response of estrogen. These results indicated that ING4 functions as a noncompetitive inhibitor of estrogen signaling and may inhibit estrogen-independent ER activity. Supportive of this, treatment with fulvestrant but not tamoxifen rendered T47D cells sensitive to hormone deprivation as did ING4 overexpression. ING4 did not affect nuclear ER alpha protein expression, but repressed selective ER-target gene transcription. Taken together, these results demonstrated that ING4 inhibited estrogen-independent ER activity, suggesting that ING4-low breast tumors recur faster due to estrogen-independent ER activity that renders tamoxifen less effective. This study puts forth fulvestrant as a proposed therapy choice for patients with ING4-low ER+ breast tumors.
    • The tumor suppressor phosphatase and tensin homolog protein (PTEN) is negatively regulated by NF-κb p50 homodimers and involves histone 3 methylation/deacetylation in UROtsa cells chronically exposed to monomethylarsonous acid

      Oliva-González, C.; Uresti-Rivera, E.E.; Galicia-Cruz, O.G.; Jasso-Robles, F.I.; Gandolfi, A.J.; Escudero-Lourdes, C.; Univ Arizona, Dept Pharmacol & Toxicol (ELSEVIER IRELAND LTD, 2017-10-05)
      UROtsa cells have been accepted as a model to study carcinogenicity mechanisms of arsenic-associated human bladder cancer. In vitro continuous exposure to monomethylarsonous acid (MMA(III)), leads UROtsa cells to commit to malignant transformation. In this process, NF-kappa beta-associated inflammatory response seems to play an important role since this transcription factor activates some minutes after cells are exposed in vitro to MMA(III) and keeps activated during the cellular malignant transformation. It is known that a slight decrease in the protein phosphatase and tensin homologue (PTEN) gene expression is enough for some cells to become malignantly transformed. Interestingly, this tumor suppressor has been proven to be negatively regulated by NF-kappa beta through binding to its gene promoter. Based on these observations we propose that NF-kappa beta may be involved in arsenic associated carcinogenesis through the negative regulation of PTEN gene expression. Changes in PTEN expression and the binding of p50 NF-kappa beta subunit to PTEN promoter were evaluated in UROtsa cells exposed for 4, 12, 20, or 24 wk to 50 nM MMA(III). Results showed that MMA(III) induced a significant decrease in PTEN expression around 20 wk exposure to MMA(III), which correlated with increased binding of p50 subunit to the PTEN promoter. Consistent with these results, ChIP assays also showed a significant decrease in H3 acetylation (H3ac) but an increase in the repression marks H3k9me3 and H327me3 in PTEN promoter when compared with not treated cells. These results suggest that the activation of NF-kappa beta by MMA(III) may participate in UROtsa cells malignant transformation through the negative regulation of PTEN expression involving p50 homodimers-mediated chromatin remodeling around the PTEN promoter.
    • Tunable high-order frequency mixing for XUV transient absorption and photoelectron spectroscopies

      Harkema, Nathan; Plunkett, Alexander; Sandhu, Arvinder; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Phys (OPTICAL SOC AMER, 2019-10-11)
      We generate tunable extreme ultraviolet emission through high-order frequency mixing between a strong near-infrared field and a weak shortwave-infrared pulse whose wavelength can be adjusted. In this two-color driving scheme, new harmonics appear in between the single-color harmonics at energies which are linear combinations of photons from the two pulses. We demonstrate the utility of tunable two-color harmonics by employing them for XUV transient absorption spectroscopy and time-resolved photoelectron spectroscopy. We show that the two-color harmonics can be used to address the dynamics associated with excited states in Helium and Oxygen which are inaccessible using single-color harmonics. Specifically, we show the ability to switch between excitation of 3p and 4p states in Helium, control of transitions to the light induced states, observe new four-wave-mixing emissions, and selectively address different principal and vibrational quantum numbers associated with Oxygen Rydberg states. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • Tunable metasurfaces with nematic liquid crystals

      Yilmaz, Nazmi; Giden, Ibrahim Halil; Bagci, Fehim Taha; Ozdemir, Aytekin; Kurt, Hamza; Takashima, Yuzuru; Ozer, Ahmet; Univ Arizona, Coll Opt Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2018)
      Intensive researches in the area of metasurfaces have provided a new insight to obtain flat and compact optical systems. In this letter, we numerically show that, highly efficient tunable beam steering effect in transmission mode is achieved at wavelength lambda = 550 nm using nematic liquid crystals (LCs) infiltrated into double sided metasurfaces. Using the electro-optical feature of LCs, the phase profile of the metasurfaces is controlled and thus, the transmitted beam is deflected within the range from -15 degrees to 15 degrees steering angles. Transparent dielectric materials are used in the designed structure that provides highly efficient beam-steering; the corresponding transmission efficiency is above 83% in the visible spectrum, which is another superiority of the proposed hybrid tunable structure over present plasmonic/metamaterial approaches. The designed metasurface still preserves its beam deflection property covering the visible spectrum and hence, such hybrid structure can be implemented for broadband electro-optically controllable beam steering applications.
    • Tunable terahertz hyperbolic metamaterial slabs and super-resolving hyperlenses

      Zhang, Hui; Jiao, Zhiyong; Mcleod, Euan; Univ Arizona, Wyant Coll Opt Sci; Univ Arizona, BI05 Inst
      Terahertz (THz) optics offer the potential to image through objects that are opaque for visible wavelengths and provide unique spectroscopic signatures for a variety of materials and quantum processes. However, the resolution of THz images suffers from the long wavelength of THz light compared to visible. Hyperbolic metamaterials provide a possible solution through the creation of super-resolving lenses and offer greater flexibility in effective refractive index than can be provided by natural materials. Most hyperbolic metamaterials function in a narrow bandwidth due to their resonant nature. In search of a broadband material, we simulate a temperature-tunable hyperbolic metamaterial composed of a multilayer stack of alternating layers of high-density polyethylene(HDPE) and indium antimonide (InSb). At a single temperature, negative effective medium permittivity is found over a small bandwidth of 0.09 THz, but by tuning over a 40 degrees C temperature range the bandwidth is increased dramatically to 1.0 THz. Furthermore, we compute the transmission and negative refraction through the multilayer stack and simulate the imaging properties of curved hyperlens stacks using slits as test objects, achieving resolutions as small as 20 mu m at 130 mu m wavelength, far below the half-wavelength diffraction limit. (C) 2020 Optical Society of America
    • Tuning the Exospace Weather Radio for Stellar Coronal Mass Ejections

      Alvarado-Gómez, Julián D.; Drake, Jeremy J.; Fraschetti, Federico; Garraffo, Cecilia; Cohen, Ofer; Vocks, Christian; Poppenhäger, Katja; Moschou, Sofia P.; Yadav, Rakesh K.; Manchester, Ward B. IV; et al. (IOP PUBLISHING LTD, 2020-05-22)
      Coronal mass ejections (CMEs) on stars other than the Sun have proven very difficult to detect. One promising pathway lies in the detection of type II radio bursts. Their appearance and distinctive properties are associated with the development of an outward propagating CME-driven shock. However, dedicated radio searches have not been able to identify these transient features in other stars. Large Alfven speeds and the magnetic suppression of CMEs in active stars have been proposed to render stellar eruptions "radio-quiet." Employing 3D magnetohydrodynamic simulations, we study the distribution of the coronal Alfven speed, focusing on two cases representative of a young Sun-like star and a mid-activity M-dwarf (Proxima Centauri). These results are compared with a standard solar simulation and used to characterize the shock-prone regions in the stellar corona and wind. Furthermore, using a flux-rope eruption model, we drive realistic CME events within our M-dwarf simulation. We consider eruptions with different energies to probe the regimes of weak and partial CME magnetic confinement. While these CMEs are able to generate shocks in the corona, those are pushed much farther out compared to their solar counterparts. This drastically reduces the resulting type II radio burst frequencies down to the ionospheric cutoff, which impedes their detection with ground-based instrumentation.
    • Tuning the interfacial spin-orbit coupling with ferroelectricity

      Fang, Mei; Wang, Yanmei; Wang, Hui; Hou, Yusheng; Vetter, Eric; Kou, Yunfang; Yang, Wenting; Yin, Lifeng; Xiao, Zhu; Li, Zhou; et al. (NATURE PUBLISHING GROUP, 2020-05-26)
      Detection and manipulation of spin current lie in the core of spintronics. Here we report an active control of a net spin Hall angle, θSHE(net), in Pt at an interface with a ferroelectric material PZT (PbZr0.2Ti0.8O3), using its ferroelectric polarization. The spin Hall angle in the ultra-thin Pt layer is measured using the inverse spin Hall effect with a pulsed tunneling current from a ferromagnetic La0.67Sr0.33MnO3 electrode. The effect of the ferroelectric polarization on θSHE(net) is enhanced when the thickness of the Pt layer is reduced. When the Pt layer is thinner than 6 nm, switching the ferroelectric polarization even changes the sign of θSHE(net). This is attributed to the reversed polarity of the spin Hall angle in the 1st-layer Pt at the PZT/Pt interface when the ferroelectric polarization is inverted, as supported by the first-principles calculations. These findings suggest a route for designing future energy efficient spin-orbitronic devices using ferroelectric control.
    • Turbulence Characteristics of Switchback and Nonswitchback Intervals Observed by Parker Solar Probe

      Bourouaine, S.; Perez, J.C.; Klein, K.G.; Chen, C.H.K.; Martinović, M.; Bale, S.D.; Kasper, J.C.; Raouafi, N.E.; Lunar and Planetary Laboratory, University of Arizona (IOP Publishing Ltd, 2020)
      We use Parker Solar Probe (PSP) in situ measurements to analyze the characteristics of solar wind turbulence during the first solar encounter covering radial distances between 35.7R o˙ and 41.7R o˙. In our analysis we isolate so-called switchback (SB) intervals (folded magnetic field lines) from nonswitchback (NSB) intervals, which mainly follow the Parker spiral field. Using a technique based on conditioned correlation functions, we estimate the power spectra of Elsasser, magnetic, and bulk velocity fields separately in the SB and NSB intervals. In comparing the turbulent energy spectra of the two types of intervals, we find the following characteristics: (1) The decorrelation length of the backward-propagating Elsasser field z - is larger in the NSB intervals than the one in the SB intervals; (2) the magnetic power spectrum in SB intervals is steeper, with spectral index close to-5/3, than in NSB intervals, which have a spectral index close to-3/2; (3) both SB and NSB turbulence are imbalanced with NSB having the largest cross-helicity, (4) the residual energy is larger in the SB intervals than in NSB, and (5) the analyzed fluctuations are dominated by Alfvénic fluctuations that are propagating in the sunward (antisunward) direction for the SB (NSB) turbulence. These observed features provide further evidence that the switchbacks observed by PSP are associated with folded magnetic field lines giving insight into their turbulence nature. © 2020. The Author(s). Published by the American Astronomical Society..
    • Turbulence in the Local Interstellar Medium and the IBEX Ribbon

      Zirnstein, E. J.; Giacalone, J.; Kumar, R.; McComas, D. J.; Dayeh, M. A.; Heerikhuisen, J.; Univ Arizona, Dept Planetary Sci (IOP PUBLISHING LTD, 2020-01-03)
      The effects of turbulence in the very local interstellar medium (VLISM) have been proposed by Giacalone & Jokipii to be important in determining the structure of the Interstellar Boundary Explorer (IBEX) ribbon via particle trapping by magnetic mirroring. We further explore this effect by simulating the motion of charged particles in a turbulent magnetic field superposed on a large-scale mean field, which we consider to be either spatially uniform or a draped field derived from a three-dimensional magnetohydrodynamic simulation. We find that the ribbon is not double-peaked, in contrast to Giacalone & Jokipii. However, the magnetic mirror force still plays an important role in trapping particles. Furthermore, the ribbon is considerably thicker if the large-scale mean field is draped around the heliosphere. Voyager 1 observations in the VLISM show a turbulent field component that is stronger than previously thought, which we test in our simulation. We find that the inclusion of turbulent fluctuations at scales greater than or similar to 100 au and power consistent with Voyager 1 observations produces a ribbon whose large-scale structure is inconsistent with IBEX observations. However, restricting fluctuations to IBEX observations. Different realizations of turbulence produce different small-scale features (less than or similar to 10 degrees) in the ribbon, but its large-scale structure is robust if the maximum fluctuation size is less than or similar to 50 au. This suggests that the magnetic field structure at scales less than or similar to 50 au is determined by the heliosphere-VLISM interaction and cannot entirely be represented by pristine interstellar turbulence.
    • Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations

      Adhikari, L.; Zank, G. P.; Zhao, L.-L.; Kasper, J. C.; Korreck, K. E.; Stevens, M.; Case, A. W.; Whittlesey, P.; Larson, D.; Livi, R.; et al. (IOP PUBLISHING LTD, 2020-02-03)
      The Parker Solar Probe (PSP) achieved its first orbit perihelion on 2018 November 6, reaching a heliocentric distance of about 0.165 au (35.55 R-circle dot). Here, we study the evolution of fully developed turbulence associated with the slow solar wind along the PSP trajectory between 35.55 R-circle dot and 131.64 R-circle dot in the outbound direction, comparing observations to a theoretical turbulence transport model. Several turbulent quantities, such as the fluctuating kinetic energy and the corresponding correlation length, the variance of density fluctuations, and the solar wind proton temperature are determined from the PSP Solar Wind Electrons Alphas and Protons (SWEAP) plasma data along its trajectory between 35.55 R-circle dot and 131.64 R-circle dot. The evolution of the PSP derived turbulent quantities are compared to the numerical solutions of the nearly incompressible magnetohydrodynamic (NI MHD) turbulence transport model recently developed by Zank et al. We find reasonable agreement between the theoretical and observed results. On the basis of these comparisons, we derive other theoretical turbulent quantities, such as the energy in forward and backward propagating modes, the total turbulent energy, the normalized residual energy and cross-helicity, the fluctuating magnetic energy, and the correlation lengths corresponding to forward and backward propagating modes, the residual energy, and the fluctuating magnetic energy.
    • Turbulent Gas in Lensed Planck-selected Starbursts at z ∼ 1-3.5

      Harrington, K.C.; Weiss, A.; Yun, M.S.; Magnelli, B.; Sharon, C.E.; Leung, T.K.D.; Vishwas, A.; Wang, Q.D.; Frayer, D.T.; Jiménez-Andrade, E.F.; et al. (IOP Publishing Ltd, 2021)
      Dusty star-forming galaxies at high redshift (1 < z < 3) represent the most intense star-forming regions in the universe. Key aspects to these processes are the gas heating and cooling mechanisms, and although it is well known that these galaxies are gas-rich, little is known about the gas excitation conditions. Only a few detailed radiative transfer studies have been carried out owing to a lack of multiple line detections per galaxy. Here we examine these processes in a sample of 24 strongly lensed star-forming galaxies identified by the Planck satellite (LPs) at z ∼ 1.1-3.5. We analyze 162 CO rotational transitions (ranging from J up = 1 to 12) and 37 atomic carbon fine-structure lines ([C i]) in order to characterize the physical conditions of the gas in the sample of LPs. We simultaneously fit the CO and [C i] lines and the dust continuum emission, using two different non-LTE, radiative transfer models. The first model represents a two-component gas density, while the second assumes a turbulence-driven lognormal gas density distribution. These LPs are among the most gas-rich, IR-luminous galaxies ever observed (μL L IR(8-1000 μm) ∼ 1013-14.6 L⊙; «μLMISM» = (2.7 ± 1.2) × 1012 Mo˙ with μL ∼ 10-30 the average lens magnification factor). Our results suggest that the turbulent interstellar medium present in the LPs can be well characterized by a high turbulent velocity dispersion («ΔVturb» ∼ 100 km s-1) and ratios of gas kinetic temperature to dust temperature «T kin/T d» ∼ 2.5, sustained on scales larger than a few kiloparsecs. We speculate that the average surface density of the molecular gas mass and IR luminosity, Σ ∼ 103-4 M o˙ pc-2 and Σ ∼ 1011-12 L o˙ kpc-2, arise from both stellar mechanical feedback and a steady momentum injection from the accretion of intergalactic gas. © 2021. The American Astronomical Society. All rights reserved.
    • Turbulent mixing induced by Richtmyer-Meshkov instability

      Krivets, V. V.; Ferguson, K. J.; Jacobs, J. W.; Univ Arizona, Dept Aerosp & Mech Engn (AMER INST PHYSICS, 2017)
      Richtmyer-Meshkov instability is studied in shock tube experiments with an Atwood number of 0.7. The interface is formed in a vertical shock tube using opposed gas flows, and three-dimensional random initial interface perturbations are generated by the vertical oscillation of gas column producing Faraday waves. Planar Laser Mie scattering is used for flow visualization and for measurements of the mixing process. Experimental image sequences are recorded at 6 kHz frequency and processed to obtain the time dependent variation of the integral mixing layer width. Measurements of the mixing layer width are compared with Mikaelian's [1] model in order to extract the growth exponent. where a fairly wide range of values is found varying from theta approximate to 0.2 to 0.6.