Now showing items 1-20 of 7865

    • Disturbance Ecology in the Anthropocene

      Newman, Erica A.; Univ Arizona, Dept Ecol & Evolut Biol (FRONTIERS MEDIA SA, 2019-05-10)
      With the accumulating evidence of changing disturbance regimes becoming increasingly obvious, there is potential for disturbance ecology to become the most valuable lens through which climate-related disturbance events are interpreted. In this paper, I revisit some of the central themes of disturbance ecology and argue that the knowledge established in the field of disturbance ecology continues to be relevant to ecosystem management, even with rapid changes to disturbance regimes and changing disturbance types in local ecosystems. Disturbance ecology has been tremendously successful over the past several decades at elucidating the interactions between disturbances, biodiversity, and ecosystems, and this knowledge can be leveraged in different contexts. Primarily, management in changing and uncertain conditions should be focused primarily on the long-term persistence of that native biodiversity that has evolved within the local disturbance regime and is likely to go extinct with rapid changes to disturbance intensity, frequency, and type. Where possible, conserving aspects of natural disturbance regimes will be vital to preserving functioning ecosystems and to that native biodiversity that requires disturbance for its continued existence, though these situations may become more limited over time. Finally, scientists must actively propose management policies that incorporate knowledge of disturbance ecology. Successful policies regarding changing disturbance regimes for biodiversity will not merely be reactive, and will recognize that for natural ecosystems as for human society, not all desired outcomes are simultaneously possible.
    • Credibility of Convection-Permitting Modeling to Improve Seasonal Precipitation Forecasting in the Southwestern United States

      Pal, Sujan; Chang, Hsin-I; Castro, Christopher L.; Dominguez, Francina; Univ Arizona, Dept Hydrol & Atmospher Sci (FRONTIERS MEDIA SA, 2019-03-05)
      Sub-seasonal to seasonal (S2S) forecasts are critical for planning and management decisions in multiple sectors. This study shows results from dynamical downscaling using a regional climate model at a convection-permitting scale driven by boundary conditions from the global reanalysis of the Climate Forecast System Model (CFSR). Convection-permitting modeling (CPM) enhances the representation of regional climate by better resolving the regional forcings and processes, associated with topography and land cover, in response to variability in the large-scale atmospheric circulation. We performed dynamically downscaled simulations with the Weather Research and Forecasting (WRF) model over the Upper and Lower Colorado basin at 12 km and 3 km grid spacing from 2000 to 2010 to investigate the potential of dynamical downscaling to improved the modeled representation of precipitation the Southwestern United States. Employing a convection-permitting nested domain of 3 km resolution significantly reduces the bias in mean (similar to 2 mm/day) and extreme (similar to 4 mm/day) summer precipitation when compared to coarser domain of 12 km resolution and coarse resolution CFSR products. The convection-permitting modeling product also better represents eastward propagation of organized convection due to mesoscale convective systems at a subdaily scale, which largely account for extreme summer rainfall during the North American monsoon. In the cool season both coarse and high-resolution simulations perform well with limited bias of similar to 1 mm/day for the mean and similar to 2 mm/day for the extreme precipitation. Significant correlation was found (similar to 0.85 for summer and similar to 0.65 for winter) for both coarse and high-resolution model with observed regionally and seasonally averaged precipitation. Our findings suggest that the use of CPM is necessary in a dynamical modeling system for S2S prediction in this region, especially during the warm season when precipitation is mostly convectively driven.
    • Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production

      Wilson, Rachel M.; Neumann, Rebecca B.; Crossen, Kelsey B.; Raab, Nicole M.; Hodgkins, Suzanne B.; Saleska, Scott R.; Bolduc, Ben; Woodcroft, Ben J.; Tyson, Gene W.; Chanton, Jeffrey P.; et al. (FRONTIERS MEDIA SA, 2019-03-29)
      The mechanisms, pathways, and rates of CO2 and CH4 production are central to understanding carbon cycling and greenhouse gas flux in wetlands. Thawing permafrost regions are of particular interest because they are disproportionally affected by climate warming and store large reservoirs of organic C that may be readily converted to CO2 and CH4 upon thaw. This conversion is accomplished by a community of microorganisms interacting in complex ways to transform large organic compounds into fatty acids and ultimately CO2 and CH4. While the central role of microbes in this process is well-known, geochemical rate models rarely integrate microbiological information. Herein, we expanded the geochemical rate model of Neumann et al., (2016, Biogeochemistry 127: 57-87) to incorporate a Bayesian probability analysis and applied the result to quantifying rates of CO2, CH4, and acetate production in closed-system incubations of peat collected from three habitats along a permafrost thaw gradient. The goals of this analysis were twofold. First, we integrated microbial community analyses with geochemical rate modeling by using microbial data to inform the best model choice among equally mathematically feasible model variants. Second, based on model results, we described changes in organic carbon transformation among habitats to understand the changing pathways of greenhouse gas production along the permafrost thaw gradient. We found that acetoclasty, hydrogenotrophy, CO2 production, and homoacetogenesis were the important reactions in this system, with little evidence for anaerobic CH4 oxidation. There was a distinct transition in the reactions across the thaw gradient. The collapsed palsa stage presents an initial disequilibrium where the abrupt (physically and temporally) change in elevation introduces freshly fixed carbon into anoxic conditions then fermentation products build up over time as the system transitions through the acid phase and electron acceptors are depleted. In the bog, fermentation slows, while methanogenesis increases. In the fully thawed fen, most of the terminal electron acceptors are depleted and the system becomes increasingly methanogenic. This suggests that as permafrost regions thaw and dry palsas transition into wet fens, CH4 emissions will rise, increasing the warming potential of these systems and accelerating climate warming feedbacks.
    • Bayesian Markov-Chain Monte Carlo Inversion of Low-Temperature Thermochronology Around Two 8 − 10 m Wide Columbia River Flood Basalt Dikes

      Karlstrom, Leif; Murray, Kendra E.; Reiners, Peter W.; Univ Arizona, Dept Geosci (FRONTIERS MEDIA SA, 2019-04-30)
      Flood basalt volcanism involves large volumes of magma emplaced into the crust and surface environment on geologically short timescales. The mechanics of flood basalt emplacement, including dynamics of the crustal magma transport system and the tempo of individual eruptions, are not well-constrained. Here we study two exhumed dikes from the Columbia River Flood Basalt province in northeast Oregon, USA, using apatite and zircon (U-Th)/He thermochronology to constrain dike emplacement histories. Sample transects perpendicular to the dike margins document transient heating of granitic host rocks. We model heating as due to dike emplacement, considering a thermal model with distinct melt-fraction temperature relationships for basaltic magma and granitic wallrock, and a parameterization of unsteady flow within the dike. We model partial resetting of thermochronometers by considering He diffusion in spherical grains as a response to dike heating. A Bayesian Markov-Chain Monte Carlo framework is used to jointly invert for six parameters related to dike emplacement and grain-scale He diffusion. We find that the two dikes, despite similar dimensions on an outcrop scale, exhibit different spatial patterns of thermochronometer partial resetting away from the dike. These patterns predict distinct emplacement histories. We extend previousmodeling of a presumed feeder dike atMaxwell Lake in theWallowaMountains of northeastern Oregon, finding posterior probability distribution functions (PDFs) that predict steady heating from sustained magma flow over 1-6 years and elevated farfield host rock temperatures. This suggests regional-scale heating in the vicinity of Maxwell Lake, which might arise from nearby intrusions. The other dike, within the Cornucopia subswarm, is predicted to have a 1-4 year thermally active lifespan with an unsteady heating rate suggestive of lowmagma flow rate compared to Maxwell Lake, in a cool near-surface thermal environment. In both cases, misfit of near-dike partial resetting of thermochronometers by models suggests either heat transfer via fluid advection in host rocks or pulsed magma flow in the dikes. Our results highlight the diversity of dike emplacement histories within the Columbia River Flood Basalt province and the power of Bayesian inversion methods for quantifying parameter trade-offs and uncertainty in thermal models.
    • The CAT Vehicle Testbed: A Simulator with Hardware in the Loop for Autonomous Vehicle Applications

      Bhadani, Rahul Kumar; Sprinkle, Jonathan; Bunting, Matthew; Univ Arizona, Dept Elect & Comp Engn (OPEN PUBL ASSOC, 2018-04-12)
      This paper presents the CAT Vehicle (Cognitive and Autonomous Test Vehicle) Testbed: a research testbed comprised of a distributed simulation-based autonomous vehicle, with straightforward transition to hardware in the loop testing and execution, to support research in autonomous driving technology. The evolution of autonomous driving technology from active safety features and advanced driving assistance systems to full sensor-guided autonomous driving requires testing of every possible scenario. However, researchers who want to demonstrate new results on a physical platform face difficult challenges, if they do not have access to a robotic platform in their own labs. Thus, there is a need for a research testbed where simulation-based results can be rapidly validated through hardware in the loop simulation, in order to test the software on board the physical platform. The CAT Vehicle Testbed offers such a testbed that can mimic dynamics of a real vehicle in simulation and then seamlessly transition to reproduction of use cases with hardware. The simulator utilizes the Robot Operating System (ROS) with a physics-based vehicle model, including simulated sensors and actuators with configurable parameters. The testbed allows multi-vehicle simulation to support vehicle to vehicle interaction. Our testbed also facilitates logging and capturing of the data in the real time that can be played back to examine particular scenarios or use cases, and for regression testing. As part of the demonstration of feasibility, we present a brief description of the CAT Vehicle Challenge, in which student researchers from all over the globe were able to reproduce their simulation results with fewer than 2 days of interfacing with the physical platform.
    • Resolution of Ring Tourniquet with a High-speed Dental Drill in a Remote Pacific Island Clinic

      Rahimian, Rombod; Lippi, Matthew; Rusaqoli, Joseph; Perez, Lidia M; Univ Arizona, Coll Med (CUREUS INC, 2019-04-16)
      Ring tourniquet syndrome is a strangulation injury, usually at the proximal finger or toe, caused by a rigid circular metal object. The resulting ischemia can lead to necrosis, permanent nerve and/or tissue damage, and amputation of the digit. There are numerous non-cutting methods for removing the ring; however, edema, fractures, or arthrosis of the site can occasionally make these techniques difficult or impossible. While ring cutters, manual or electric, are the first choice for resolving ring tourniquet caused by metal jewelry, these tools are not readily available everywhere. Resolution of ring tourniquet with high-speed rotary tools has been previously described as a tertiary method. Here we describe the use of a high-speed dental tool as a primary ring cutting method for the resolution of ring tourniquet in a patient with significant edema in a low-resource setting.
    • Core Cosmology Library: Precision Cosmological Predictions for LSST

      Chisari, Nora Elisa; Alonso, David; Krause, Elisabeth; Leonard, C. Danielle; Bull, Philip; Neveu, Jérémy; Villarreal, Antonio; Singh, Sukhdeep; McClintock, Thomas; Ellison, John; et al. (IOP PUBLISHING LTD, 2019-05-01)
      The Core Cosmology Library (CCL) provides routines to compute basic cosmological observables to a high degree of accuracy, which have been verified with an extensive suite of validation tests. Predictions are provided for many cosmological quantities, including distances, angular power spectra, correlation functions, halo bias, and the halo mass function through state-of-the-art modeling prescriptions available in the literature. Fiducial specifications for the expected galaxy distributions for the Large Synoptic Survey Telescope (LSST) are also included, together with the capability of computing redshift distributions for a user-defined photometric redshift model. A rigorous validation procedure, based on comparisons between CCL and independent software packages, allows us to establish a well-defined numerical accuracy for each predicted quantity. As a result, predictions for correlation functions of galaxy clustering, galaxy-galaxy lensing, and cosmic shear are demonstrated to be within a fraction of the expected statistical uncertainty of the observables for the models and in the range of scales of interest to LSST. CCL is an open source software package written in C, with a Python interface and publicly available at. https://github.com/LSSTDESC/CCL.
    • Line Ratios Reveal N2H+ Emission Originates above the Midplane in TW Hydrae

      Schwarz, Kamber R.; Teague, Richard; Bergin, Edwin A.; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2019-05-03)
      Line ratios for different transitions of the same molecule have long been used as a probe of gas temperature. Here we use ALMA observations of the N2H+ J= 1-0 and J = 4-3 lines in the protoplanetary disk around TW Hya to derive the temperature at which these lines emit. We find an averaged temperature of 39 K with a 1 sigma uncertainty of 2 K for the radial range 0.'' 8-2 '', which is significantly warmer than the expected midplane temperature beyond 0 ''.5 in this disk. We conclude that the N2H+ emission in TW Hya is not emitting from near the midplane, but rather from higher in the disk, in a region likely bounded by processes such as photodissociation or chemical reprocessing of CO and N-2 rather than freeze-out.
    • Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns

      Cui, J.; Cao, Y.-T.; Wu, X.-S.; Xu, S.-S.; Yelle, R. V.; Stone, S.; Vigren, E.; Edberg, N. J. T.; Shen, C.-L.; He, F.; et al. (IOP PUBLISHING LTD, 2019-05-03)
      Combining the Mars Atmosphere and Volatile Evolution (MAVEN) measurements of atmospheric neutral and ion densities, electron temperature, and energetic electron intensity, we perform the first quantitative evaluation of local ionization balance in the nightside Martian upper atmosphere, a condition with the electron impact ionization (EI) of CO2 exactly balanced by the dissociative recombination (DR) of ambient ions. The data accumulated during two MAVEN Deep Dip (DD) campaigns are included: DD6 on the deep nightside with a periapsis solar zenith angle (SZA) of 165 degrees, and DD3 close to the dawn terminator with a periapsis SZA of 110 degrees. With the electron temperatures at low altitudes corrected for an instrumental effect pertaining to the MAVEN Langmuir Probe and Waves, a statistical agreement between the EI and DR rates is suggested by the data below 140 km during DD6 and below 180 km during DD3, implying that electron precipitation is responsible for the nightside Martian ionosphere under these circumstances and extra sources are not required. In contrast, a substantial enhancement in EI over DR is observed at higher altitudes during both campaigns, which we interpret as a signature of plasma escape down the tail.
    • Fate of the Runner in Hit-and-run Collisions

      Emsenhuber, Alexandre; Asphaug, Erik; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2019-04-19)
      In similar-sized planetary collisions, a significant part of the impactor often misses the target and continues downrange. We follow the dynamical evolution of. "runners" from giant impacts to determine their ultimate fate. Surprisingly, runners reimpact their target planets only about half of the time for realistic collisional and dynamical scenarios. Otherwise, they remain in orbit for tens of millions of years (the limit of our N-body calculations) and longer, or they sometimes collide with a different planet than the first one. When the runner does return to collide again with the same target planet, its impact velocity is mainly constrained by the outcome of the prior collision. Impact angle and orientation, however, are unconstrained by the prior collision.
    • Kinematics of the Broad-line Region of 3C 273 from a 10 yr Reverberation Mapping Campaign

      Zhang, Zhi-Xiang; Du, Pu; Smith, Paul S.; Zhao, Yulin; Hu, Chen; Xiao, Ming; Li, Yan-Rong; Huang, Ying-Ke; Wang, Kai; Bai, Jin-Ming; et al. (IOP PUBLISHING LTD, 2019-05-01)
      Despite many decades of study, the kinematics of the broad-line region of 3C 273 are still poorly understood. We report a new, high signal-to-noise, reverberation mapping campaign carried out from 2008 November to 2018 March that allows the determination of time lags between emission lines and the variable continuum with high precision. The time lag of variations in H beta relative to those of the 5100 angstrom continuum is 146.8(-1)(2.1)(+8.3) days in the rest frame, which agrees very well with the Paschen-alpha region measured by the GRAVITY at The Very Large Telescope Interferometer. The time lag of the H gamma emission line is found to be nearly the same as that for H beta. The lag of the Fe II emission is 322.0(-57)(.9)(+55.5) days, longer by a factor of similar to 2 than that of the Balmer lines. The velocity-resolved lag measurements of the H beta line show a complex structure that can be possibly explained by a rotation-dominated disk with some inflowing radial velocity in the H beta-emitting region. Taking the virial factor of f(BLR) = 1.3, we derive a BH mass of M. = 4.1(-0.4)(+0.3) x 10(8) M-circle dot and an accretion rate of 9.3 L-Edd C-2 from the H beta line. The decomposition of its Hubble Space Telescope images yields a host stellar mass of M-* = 10(11.)(3 +/- 0.7) M-circle dot, and a ratio of M./M-* approximate to 2.0 x 10(-3) in agreement with the Magorrian relation. In the near future, it is expected to compare the geometrically thick BLR discovered by the GRAVITY in 3C 273 with its spatially resolved torus in order to understand the potential connection between the BLR and the torus.
    • The Influence of Host Star Spectral Type on Ultra-hot Jupiter Atmospheres

      Lothringer, Joshua D.; Barman, Travis; Univ Arizona, Lunar & Planetary Lab (IOP PUBLISHING LTD, 2019-05-06)
      Ultra-hot Jupiters are the most highly irradiated gas giant planets, with equilibrium temperatures from 2000 to over 4000 K. Ultra-hot Jupiters are amenable to characterization due to their high temperatures, inflated radii, and short periods, but their atmospheres are atypical for planets in that the photosphere possesses large concentrations of atoms and ions relative to molecules. Here we evaluate how the atmospheres of these planets respond to irradiation by stars of different spectral type. We find that ultra-hot Jupiters exhibit temperature inversions that are sensitive to the spectral type of the host star. The slope and temperature range across the inversion both increase as the host star effective temperature increases due to enhanced absorption at short wavelengths and low pressures. The steep temperature inversions in ultra-hot Jupiters around hot stars result in increased thermal dissociation and ionization compared to similar planets around cooler stars. The resulting increase in H- opacity leads to a transit spectrum that has muted absorption features. The emission spectrum, however, exhibits a large contrast in brightness temperature, a signature that will be detectable with both secondary eclipse observations and high-dispersion spectroscopy. We also find that the departures from local thermodynamic equilibrium in the stellar atmosphere can affect the degree of heating caused by atomic metals in the planet's upper atmosphere. Additionally, we further quantify the significance of heating by different opacity sources in ultra-hot Jupiter atmospheres.
    • Fluorine Abundances in the Globular Cluster M4

      Guerço, Rafael; Cunha, Katia; Smith, Verne V.; Pereira, Claudio B.; Abia, Carlos; Lambert, David L.; de Laverny, Patrick; Recio-Blanco, Alejandra; Jönsson, Henrik; Univ Arizona (IOP PUBLISHING LTD, 2019-05-01)
      We present chemical abundances for the elements carbon, sodium, and fluorine in 15 red giants of the globular cluster M4, as well as six red giants of the globular cluster w Centauri. The chemical abundances were calculated in LTE via spectral synthesis. The spectra analyzed are high-resolution spectra obtained in the near-infrared region around 2.3 mu m with the Phoenix spectrograph on the 8.1 m Gemini South Telescope, the IGRINS spectrograph on the McDonald Observatory 2.7 m Telescope, and the CRIRES spectrograph on the ESO 8.2 m Very Large Telescope. The results indicate a significant reduction in the fluorine abundances when compared to previous values from the literature for M4 and w Centauri, due to a downward revision in the excitation potentials of the HF (1-0) R9 line used in the analysis. The fluorine abundances obtained for the M4 red giants are found to be anticorrelated with those of Na, following the typical pattern of abundance variations seen in globular clusters between distinct stellar populations. In M4, as the Na abundance increases by similar to+0.4 dex, the F abundance decreases by similar to-0.2 dex. A comparison with abundance predictions from two sets of stellar evolution models finds that the models predict somewhat less F depletion (similar to-0.1 dex) for the same increase of +0.4 dex in Na.
    • Star Formation and ISM Properties in the Host Galaxies of Three Far-infrared Luminous Quasars at z ∼ 6

      Shao, Yali; Wang, Ran; Carilli, Chris L.; Wagg, Jeff; Walter, Fabian; Li, Jianan; Fan, Xiaohui; Jiang, Linhua; Riechers, Dominik A.; Bertoldi, Frank; et al. (IOP PUBLISHING LTD, 2019-05-08)
      We present Karl G. Jansky Very Large Array observations of the CO (2-1) line emission toward three far-infrared luminous quasars at z similar to 6: SDSS J231038.88+ 185519.7 and SDSS J012958.51-003539.7 with similar to 0.'' 6 resolution and SDSS J205406.42-000514.8 with similar to 2.'' 1 resolution. All three sources are detected in the CO (2-1) line emission-one source is marginally resolved, and the other two appear as point sources. Measurements of the CO (2-1) line emission allow us to calculate the molecular gas mass even without a CO excitation model. The inferred molecular gas masses are (0.8-4.3) x 10(10) M-circle dot. The widths and redshifts derived from the CO (2-1) line are consistent with previous CO (6-5) and [C II] measurements. We also report continuum measurements using Herschel for SDSS J231038.88+ 185519.7 and SDSS J012958.51-003539.7, and for SDSS J231038.88 + 185519.7 data obtained at similar to 140 and similar to 300 GHz using the Atacama Large Millimeter/submillimeter Array. In the case of SDSS J231038.88+ 185519.7, we present a detailed analysis of the spectral energy distribution and derive the dust temperature (similar to 40 K), the dust mass (similar to 10(9) M-circle dot), the far-infrared luminosity (8-1000 mu m; similar to 10(13) L-circle dot), and the star formation rate (2400-2700 M-circle dot yr(-1)). Finally, an analysis of the photodissociation regions associated with the three high-redshift quasars indicates that the interstellar medium in these sources has similar properties to local starburst galaxies.
    • Extreme Debris Disk Variability: Exploring the Diverse Outcomes of Large Asteroid Impacts During the Era of Terrestrial Planet Formation

      Su, Kate Y. L.; Jackson, Alan P.; Gáspár, András; Rieke, George H.; Dong, Ruobing; Olofsson, Johan; Kennedy, G. M.; Leinhardt, Zoë M.; Malhotra, Renu; Hammer, Michael; et al. (IOP PUBLISHING LTD, 2019-04-30)
      The most dramatic phases of terrestrial planet formation are thought to be oligarchic and chaotic growth, on timescales of up to 100-200 Myr, when violent impacts occur between large planetesimals of sizes up to protoplanets. Such events are marked by the production of large amounts of debris, as has been observed in some exceptionally bright and young debris disks (termed extreme debris disks). Here we report five years of Spitzer measurements of such systems around two young solar-type stars: ID8 and P1121. The short-term (weekly to monthly) and long-term (yearly) disk variability is consistent with the aftermaths of large impacts involving large asteroid-sized bodies. We demonstrate that an impact-produced clump of optically thick dust, under the influence of the dynamical and viewing geometry effects, can produce short-term modulation in the disk light curves. The long-term disk flux variation is related to the collisional evolution within the impact-produced fragments once released into a circumstellar orbit. The time-variable behavior observed in the P1121 system is consistent with a hypervelocity impact prior to 2012 that produced vapor condensates as the dominant impact product. Two distinct short-term modulations in the ID8 system suggest two violent impacts at different times and locations. Its long-term variation is consistent with the collisional evolution of two different populations of impact-produced debris dominated by either vapor condensates or escaping boulders. The bright, variable emission from the dust produced in large impacts from extreme debris disks provides a unique opportunity to study violent events during the era of terrestrial planet formation.
    • Mechanisms of cannabinoid CB2 receptor-mediated reduction of dopamine neuronal excitability in mouse ventral tegmental area

      Ma, Zegang; Gao, Fenfei; Larsen, Brett; Gao, Ming; Luo, Zhihua; Chen, Dejie; Ma, Xiaokuang; Qiu, Shenfeng; Zhou, Yu; Xie, Junxia; et al. (ELSEVIER SCIENCE BV, 2019-01-03)
      Background: We have recently reported that activation of cannabinoid type 2 receptors (CB(2)Rs) reduces dopamine (DA) neuron excitability in mouse ventral tegmental area (VTA). Here, we elucidate the underlying mechanisms. Methods: Patch-clamp recordings were performed in mouse VTA slices and dissociated single VTA DA neurons. Findings: Using cell-attached recording in VTA slices, bath-application of CB2R agonists (JWH133 or five other CB2R agonists) significantly reduced VTA DA neuron action potential (AP) firing rate. Under the patch-clamp whole-cell recordingmodel, JWH133 (10 mu M) mildly reduced the frequency ofminiature excitatory postsynaptic currents (mEPSCs) but not miniature inhibitory postsynaptic currents (mIPSCs). JWH133 also did not alter evoked EPSCs or IPSCs. In freshly dissociated VTA DA neurons, JWH133 reduced AP firing rate, delayed AP initiation and enhanced AP after-hyperpolarization. In voltage-clamp recordings, JWH133 (1 mu M) enhanced M-type K+ currents and this effect was absent in CB -/-mice and abolished by co-administration of a selective CB2R antagonist (10 mu M, AM630). CB2R-mediated inhibition in VTA DA neuron firing can be mimicked by M-current opener (10 mu M retigabine) and blocked by M-current blocker (30 mu M XE991). In addition, enhancement of neuronal cAMP by forskolin (10 mu M) reduced M-current and increased DA neuron firing rate. Finally, pharmacological block of synaptic transmission by NBQX (10 mu M), D-APV (50 mu M) and picrotoxin (100 mu M) in VTA slices failed to prevent CB2R-mediated inhibition, while intracellular infusion of guanosine 5'-O-2-thiodiphosphate (600 mu M, GDP-beta-S) through recording electrode to block postsynaptic G-protein function prevented JWH133-induced reduction in AP firing. Interpretation: Our results suggest that CB2Rs modulate VTA DA neuron excitability mainly through an intrinsic mechanism, including a CB2R-mediated reduction of intracellular cAMP, and in turn enhancement of M-type K+ currents.
    • Cystic Fibrosis Transmembrane Conductance Regulator Genotype, Not Circulating Catecholamines, Influences Cardiovascular Function in Patients with Cystic Fibrosis

      Bisch, Alexander L; Wheatley, Courtney M; Baker, Sarah E; Peitzman, Elizabeth R; Van Iterson, Erik H; Laguna, Theresa A; Morgan, Wayne J; Snyder, Eric M; Univ Arizona, Arizona Resp Ctr (SAGE PUBLICATIONS LTD, 2019-03-29)
      BACKGROUND: Cystic fibrosis (CF) is a genetic disease affecting multiple organ systems of the body and is characterized by mutation in the gEne coding for the cystic fibrosis transmembrane conductance regulator (CFTR). Previous work has shown that a single dose of a beta-agonist increases cardiac output (Q) and stroke volume (SV) and decreases systemic vascular resistance (SVR) in healthy subjects. This effect is attenuated in patients with CF; however, the mechanism is unknown. Potential explanations for this decreased cardiovascular response to a beta-agonist in CF include inherent cardiovascular deficits secondary to the CFTR mutation, receptor desensitization from prolonged beta-agonist use as part of clinical care, or inhibited drug delivery to the bloodstream due to mucus buildup in the lungs. This study sought to determine the effects of endogenous epinephrine (EPI) and norepinephrine (NE) on cardiovascular function in CF and to evaluate the relationship between cardiovascular function and CFTR F508del mutation. METHODS: A total of 19 patients with CF and 31 healthy control subjects completed an assessment of Q (C2H2 rebreathing), SV (calculated from Q and heart rate [HR]), Q and SV indexed to body surface area (BSA. Ql. and SVI. respectively). SVR (through assessment of Q and mean arterial blood pressure [MAP]). and HR (from 12-lead electrocardiogram [ECG]) at rest along with plasma measures of EPI and NE. We compared subjects by variables of cardiovascular function relative to EPI and NE, and also based on genetic variants of the F508del mutation (homozygous deletion for F508del. heterozygous deletion for F508del, or no deletion of F508del). RESULTS: Cystic fibrosis patients demonstrated significantly lower BSA (CF = 1.71 +/- 0.05 m(2) vs healthy = 1.84 +/- 0.04 m(2), P = .03) and SVI (CF = 30.6 +/- 2.5 mL/beat/m(2) vs healthy = 39.9 +/- 2.5 mL/beat/m(2) , P = .02) when compared with healthy subjects. Cystic fibrosis patients also demonstrated lower Q (CF = 4.58 +/- 0.36 L/min vs healthy = 5.71 +/- 0.32 L/min, P = .03) and SV (CF = 54 +/- 5.5 mL/beat vs healthy = 73.3 +/- 4.5 mL/beat. P = .01), and a higher HR (CF = 93.2 +/- 3.9 bpm vs healthy = 80.5 +/- 2.7 bpm, P < .01) and SVR (CF = 2082 +/- 156 dynes(*)s/cm(-5) vs healthy = 1616 +/- 74 dynes*s/cm(-5), P= .01) compared with healthy subjects. Furthermore. CF patients demonstrated a lower SV (P < .01) corrected for NE when compared with healthy subjects. No significant differences were seen in HR or Q relative to NE. or SVR relative to EPI. Differences were seen in SV(F-(2,F-14) = 7.982, P < .01) and SV index (F-(2(,14)) = 2.913, P = .08) when patients with CF were stratified according to F508del mutation (number of deletions). CONCLUSIONS: Individuals with CF have lower cardiac and peripheral hemodynamic function parameters at rest. Furthermore, these results suggest that impairment in cardiovascular function is likely the result of F508del CFTR genotype, rather than receptor desensitization or inhibited drug delivery.
    • The Effect of Genetically Guided Mathematical Prediction and the Blood Pressure Response to Pharmacotherapy in Hypertension Patients

      Kelley, Eli F; Olson, Thomas P; Curry, Timothy B; Sprissler, Ryan; Snyder, Eric M; Univ Arizona, Dept Genet, Genom Core (SAGE PUBLICATIONS LTD, 2019-05-03)
      PURPOSE: The purpose of this study was to determine the effectiveness of a simple algorithm to mathematically predict a patients' response to blood pressure (BP) therapy using functional genes in the 3 major organ systems involved in hypertension. METHODS: Eighty-six patients with controlled hypertension completed 1 study visit consisting of a buccal swab collection. measurement of office BP, and a medical chart review for BP history. Genes in the analysis included 14 functional alleles in 11 genes. These genotypes were mathematically summed per organ system to determine whether a patient would likely respond to target therapy. RESULTS: Patients recommended to and taking a diuretic had significantly higher rates of control (<120/<80) than patients recommended but not taking this drug class (0.2 +/- 0.1 and 0.03 +/- 0.03, respectively). Furthermore. there was a difference between patients genetically recommended and taking an angiotensin receptor blocker (ARB) vs patients recommended but not taking an ARB for the lowest diastolic blood pressure (DBP) and mean arterial pressure (MAP) recorded in the past 2 years (DBP = 66.2 +/- 2.9 and 75.3 +/- 1.7, MAP = 82.3 +/- 2.8 and 89.3 +/- 1.5, respectively). In addition, there was a nonsignificant trend for greater reductions in Delta SBP, Delta DBP, and Delta MAP in patients on recommended drug class for beta-blockers. diuretics. and angiotensin II receptor blockers vs patients not on these classes. CONCLUSION: The present study suggests that simple mathematical weighting of functional genotypes known to control BP may be ineffective in predicting control. This study demonstrates the need for a more complex. weighted. multigene algorithm to more accurately predict BP therapy response.
    • The Intraseasonal and Interannual Variability of Arctic Temperature and Specific Humidity Inversions

      Yu, Lejiang; Yang, Qinghua; Zhou, Mingyu; Zeng, Xubin; Lenschow, Donald H.; Wang, Xianqiao; Han, Bo; Univ Arizona, Dept Atmospher Sci (MDPI, 2019-04-22)
      Temperature and humidity inversions are common in the Arctic's lower troposphere, and are a crucial component of the Arctic's climate system. In this study, we quantify the intraseasonal oscillation of Arctic temperature and specific humidity inversions and investigate its interannual variability using data from the Surface Heat Balance of the Arctic (SHEBA) experiment from October 1997 to September 1998 and the European Centre for Medium-Range Forecasts (ECMWF) Reanalysis (ERA)-interim for the 1979-2017 period. In January 1998, there were two noticeable elevated inversions and one surface inversion. The transitions between elevated and surface-based inversions were associated with the intraseasonal variability of the temperature and humidity differences between 850 and 950 hPa. The self-organizing map (SOM) technique is utilized to obtain the main modes of surface and elevated temperature and humidity inversions on intraseasonal time scales. Low (high) pressure and more (less) cloud cover are related to elevated (surface) temperature and humidity inversions. The frequency of strong (weak) elevated inversions over the eastern hemisphere has decreased (increased) in the past three decades. The wintertime Arctic Oscillation (AO) and Arctic Dipole (AD) during their positive phases have a significant effect on the occurrence of surface and elevated inversions for two Nodes only.
    • Ultra-diffuse Galaxies at Ultraviolet Wavelengths

      Singh, Pranjal Rajendra; Zaritsky, Dennis; Donnerstein, Richard; Spekkens, Kristine; Univ Arizona, Steward Observ (IOP PUBLISHING LTD, 2019-05-06)
      We measure near-ultraviolet (NUV) aperture magnitudes from Galaxy Evolution Explorer images for 258 ultra-diffuse galaxy (UDG) candidates drawn from the initial Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey of similar to 300 square degrees surrounding, and including, the Coma galaxy cluster. For the vast majority, 242 of them, we present flux upper limits due either to a lack of significant flux in the aperture or confusion with other objects projected within the aperture. These limits often place interesting constraints on the UDG candidates, indicating that they are non-star-forming or quiescent. In particular, we identify field, quiescent UDG candidates, which are a challenge for formation models and are, therefore, compelling prospects for spectroscopic follow-up and distance determinations. We present far-ultraviolet (FUV) and NUV magnitudes for 16 detected UDG candidates and compare those galaxies to the local population of galaxies on color-magnitude and specific star formation rate diagrams. The NUV-detected UDG candidates form mostly an extension toward lower stellar masses of the star-forming galaxy sequence, and none of these lie within regions of high local galaxy density. UDG candidates span a range of properties, although almost all are consistent with being quiescent, low surface brightness galaxies, regardless of environment.