16 research outputs found

    The symptomatic empty sella

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    Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two coexisting arid-zone coniferous trees?

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    Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation-tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller interconduit pits to reduce vulnerability to embolism but more phloem tissue and larger phloem conduits compared with plants that avoid desiccation. These anatomical differences could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses, we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of 2 coniferous species: one-seed juniper (Juniperus monosperma) and pinon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size

    First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

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    © 2019. The American Astronomical Society.. When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ±3 μas, which is circular and encompasses a central depression in brightness with a flux ratio ≈10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M =(6.5 ±0.7) ×10 9 M o . Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible

    Pru p 7 sensitization is a predominant cause of severe, cypress pollen‐associated peach allergy

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    International audienceBACKGROUND:Peach is a common elicitor of food allergic reactions. Peach-induced immediate reactions may occur as benign pollen-food syndromes, usually due to birch pollen-related PR-10 cross-reactivity in temperate climates, and as potentially severe primary food allergies, predominantly related to nsLTP Pru p 3 in Mediterranean regions. The newly described peach allergen Pru p 7 has gained recent attention as a potential peach allergy severity marker. Sensitization to Pru p 7 and its allergenic homologues of the gibberellin-regulated protein family occurs in areas with high Cupressaceae tree pollen exposure.OBJECTIVE:We sought to investigate the distribution, clinical characteristics and molecular associations of Pru p 7 sensitization among subjects with suspected peach allergy in different regions of France.METHODS:Subjects with suspected peach allergy (n = 316) were included. Diagnostic work-up was performed according to current guidelines, including open food challenge when required. IgE antibody measurements and competition experiments were performed using the ImmunoCAP assay platform.RESULTS:Sensitization to Pru p 7 was present in 171 (54%) of all subjects in the study and in 123 of 198 (62%) diagnosed as peach allergic, more than half of whom were sensitized to no other peach allergen. Frequency and magnitude of Pru p 7 sensitization were associated with the presence of peach allergy, the clinical severity of peach-induced allergic reactions and the level of cypress pollen exposure. Cypress pollen extract completely outcompeted IgE binding to Pru p 7. Pru p 7 was extremely potent in basophil activation tests.CONCLUSION AND CLINICAL RELEVANCE:A subtype of Cupressaceae pollinosis, characterized by Pru p 7 sensitization, can be an underlying cause of severe peach allergy

    Approaching the knee with direct measurements

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    45sireservedThe Cosmic Ray Energetics And Mass (CREAM) experiment was designed and constructed to push spectral measurements of individual cosmic-ray nuclei from H to Fe to energies approaching the “knee” in a series of balloon flights. A cumulative exposure of 70 days was achieved during two circumpolar flights in Antarctica in 2005 and 2006. Direct measurements at the top of the atmosphere allow event-by-event determination of the incident cosmic-ray particle charge and energy. The objective is to investigate whether and how the knee structure is related to the mechanisms of particle acceleration, propagation, and confinement. The recovered payload is being refurbished for its third flight, which is scheduled for launch in December 2007. The combination of sophisticated particle detectors and long duration balloon flight capabilities now promise high quality measurements over an energy range that was not previously accessible.mixedSeo, E.S.; Ahn, H.S.; Allison, P.; Bagliesi, M.G.; Barbier, L.; Barrau, A.; Bazer-Bachi, R.; Beatty, J. J.; Bigongiari, G.; Boyle, P.; Brandt, T.T.; Bunerd, M.; Childers, J.T.; Conklin, N.B.; Coutu, S.; Derome, L.; Duvernois, M.A; Ganel, O.; Han, J.H.; Jeon, J.A.; Kim, K. C.; Lee, M. H.; Lutz, L.; Malinin, A.; Mangin-Brinet, M.; Marrocchesi, P.S.; Maestro, P.; Menchaca-Rocha, A.; Minnick, S.; Mognet, S.I.; Nam, S. W.; Nutter, S.; Park, I. H.; Park, N. H.; Putze, A.; Sallaz-Damaz, Y.; Sina, R.; Swordy, S.; Wakely, S.; Walpole, P.; Wu, J.; Yang, J.; Yoon, Y.S.; Zei, R.; Zinn, S.Y.Seo, E. S.; Ahn, H. S.; Allison, P.; Bagliesi, MARIA GRAZIA; Barbier, L.; Barrau, A.; Bazer Bachi, R.; Beatty, J. J.; Bigongiari, Gabriele; Boyle, P.; Brandt, T. T.; Bunerd, M.; Childers, J. T.; Conklin, N. B.; Coutu, S.; Derome, L.; Duvernois, M. A; Ganel, O.; Han, J. H.; Jeon, J. A.; Kim, K. C.; Lee, M. H.; Lutz, L.; Malinin, A.; Mangin Brinet, M.; Marrocchesi, PIER SIMONE; Maestro, Paolo; Menchaca Rocha, A.; Minnick, S.; Mognet, S. I.; Nam, S. W.; Nutter, S.; Park, I. H.; Park, N. H.; Putze, A.; Sallaz Damaz, Y.; Sina, R.; Swordy, S.; Wakely, S.; Walpole, P.; Wu, J.; Yang, J.; Yoon, Y. S.; Zei, Riccardo; Zinn, S. Y
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