2,371 research outputs found

    Synthetic synchrotron emission maps from MHD models for the jet of M87

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    We present self-consistent global, steady-state MHD models and synthetic optically thin synchrotron emission maps for the jet of M87. The model consist of two distinct zones: an inner relativistic outflow, which we identify with the observed jet, and an outer cold disk-wind. While the former does not self-collimate efficiently due to its high effective inertia, the latter fulfills all the conditions for efficient collimation by the magneto-centrifugal mechanism. Given the right balance between the effective inertia of the inner flow and the collimation efficiency of the outer disk wind, the relativistic flow is magnetically confined into a well collimated beam and matches the measurements of the opening angle of M87 over several orders of magnitude in spatial extent. The synthetic synchrotron maps reproduce the morphological structure of the jet of M87, i.e. center-bright profiles near the core and limb-bright profiles away from the core. At the same time, they also show a local increase of brightness at some distance along the axis associated to a recollimation shock in the MHD model. Its location coincides with the position of the optical knot HST-1. In addition our best fitting model is consistent with a number of observational constraints such as the magnetic field in the knot HST-1, and the jet-to-counterjet brightness ratio.Comment: 9 pages, 9 figures, accepted by Ap

    Strong HI Lyman-α\alpha variations from the 11 Gyr-old host star Kepler-444: a planetary origin ?

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    Kepler-444 provides a unique opportunity to probe the atmospheric composition and evolution of a compact system of exoplanets smaller than the Earth. Five planets transit this bright K star at close orbital distances, but they are too small for their putative lower atmosphere to be probed at optical/infrared wavelengths. We used the Space Telescope Imaging Spectrograph instrument onboard the Hubble Space Telescope to search for the signature of the planet's upper atmospheres at six independent epochs in the Ly-α\alpha line. We detect significant flux variations during the transits of both Kepler-444e and f (~20%), and also at a time when none of the known planets was transiting (~40%). Variability in the transition region and corona of the host star might be the source of these variations. Yet, their amplitude over short time scales (~2-3 hours) is surprisingly strong for this old (11.2+-1.0Gyr) and apparently quiet main-sequence star. Alternatively, we show that the in-transits variations could be explained by absorption from neutral hydrogen exospheres trailing the two outer planets (Kepler-444e and f). They would have to contain substantial amounts of water to replenish such hydrogen exospheres, which would reveal them as the first confirmed ocean-planets. The out-of-transit variations, however, would require the presence of a yet-undetected Kepler-444g at larger orbital distance, casting doubt on the planetary origin scenario. Using HARPS-N observations in the sodium doublet, we derived the properties of two Interstellar Medium clouds along the line-of-sight toward Kepler-444. This allowed us to reconstruct the stellar Ly-α\alpha line profile and to estimate the XUV irradiation from the star, which would still allow for a moderate mass loss from the outer planets after 11.2Gyr. Follow-up of the system at XUV wavelengths will be required to assess this tantalizing possibility.Comment: Accepted for publication in A&A Name of the system added to the title in most recent versio

    Cosmological perturbations and short distance physics from Noncommutative Geometry

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    We investigate the possible effects on the evolution of perturbations in the inflationary epoch due to short distance physics. We introduce a suitable non local action for the inflaton field, suggested by Noncommutative Geometry, and obtained by adopting a generalized star product on a Friedmann-Robertson-Walker background. In particular, we study how the presence of a length scale where spacetime becomes noncommutative affects the gaussianity and isotropy properties of fluctuations, and the corresponding effects on the Cosmic Microwave Background spectrum.Comment: Published version, 16 page

    Gambaran Pengetahuan, Sikap dan Tindakan Pencarian Pengobatan pada Mahasiswa Fakultas Kedokteran UKI Angkatan 2012

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    Pencarian pengobatan merupakan suatu usaha yang dilakukan individu bila terkena masalah kesehatan untuk memperoleh kesembuhan atau terlepas dari masalah kesehatan tersebut. Pencarian pengobatan dapat berbeda pada masing-masing individu. Penelitian ini bertujuan untuk mengetahui pencarian pengobatan pada mahasiswa Fakultas Kedokteran UKI Angkatan 2012 dan ditinjau dari sisi pengetahuan, sikap dan tindakan dalam pencarian pengobatan. Penelitian ini menggunakan kuisioner yang diberikan kepada 158 responden untuk menggali informasi. Berdasarkan hasil penelitian, pengetahuan responden mengenai pelayanan kesehatan dan pengobatan untuk mendukung pencarian pengobatan dalam penelitian ini baik. Sebagian besar responden penelitian ini mempertimbangkan jarak dan harga ketika memilih pelayanan kesehatan (79,1%). Sebagian besar responden beranggapan bahwa pengobatan dapat dilakukan sendiri (67,7%) dengan obat yang dibeli di apotik dan berdasarkan pengetahuan sendiri. Hampir seluruh responden segera mencari pengobatan (58,2%) ketika merasa terdapat masalah pada kesehatan dan berusaha mengobati diri sendiri terlebih dahulu dengan obat yang telah disimpan atau membeli obat di apotik/warung. Hampir seluruh responden akan pergi mencari pengobatan di rumah sakit (74,1%) dibandingkan ke pengobatan tradisional dan/atau alternatif (28,5%). Kesimpulan dari penelitian ini adalah mahasiswa Fakultas Kedokteran UKI Angkatan 2012 memiliki pengetahuan yang baik untuk mendukung pencarian pengobatan serta sikap dan tindakan yang cenderung mengobati diri sendiri atau mencari pengobatan ke rumah sakit. Kata kunci : perilaku, pengobatan, pencarian pengobatan Health seeking behaviour is an attempt by individuals to obtain a cure when exposed to health problems. Health seeking behaviour can be different for each individual. This research aims to determine the health seeking behaviour in students of the Faculty of Medicine Christian University of Indonesia batch 2012 observed from their knowledge, attitude and action. This research used a questionnaire given to 158 respondents to seek information. Based on the results of the research, the respondents have good knowledge about health care services and medications to support their health seeking behaviour. Most of the respondents consider the distance and price when choosing a health care service (79.1%). Most respondents believe that the treatment can be done alone (67.7%) with drugs purchased at pharmacies and can be based on their own knowledge. Almost all respondents immediately seek treatment (58.2%) when they feel that they have a health problem and tried to treat themselves first with a drug they keep at home or drugs bought at pharmacies/stalls. Almost all respondents chose to seek treatment in hospitals (74,1%) instead of traditional and/or alternative treatment centers (28.5%). The conclusion of this research is that the students of the Faculty of Medicine Christian University of Indonesia batch 2012 has good knowledge to support their search for treatment and also can be seen through their tendency to treat themselves or seek treatment to the hospital. Key word : behaviour, medication, health seeking behavio

    Experimental and theoretical investigation of ThGeO4 at high pressure

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    We report here the combined results of angle-dispersive x-ray diffraction experiments performed on ThGeO4 up to 40 GPa and total-energy density-functional theory calculations. Zircon-type ThGeO4 is found to undergo a pressure-driven phase transition at 11 GPa to the tetragonal scheelite structure. A second phase transition to a monoclinic M-fergusonite type is found beyond 26 GPa. The same transition has been observed in samples that crystallize in the scheelite phase at ambient pressure. No additional phase transition or evidence of decomposition of ThGeO4 has been detected up to 40 GPa. The unit-cell parameters of the monoclinic high-pressure phase are a=4.98(2) Å, b=11.08(4) Å, c=4.87(2) Å, and β=90.1(1), Z=4 at 28.8 GPa. The scheelite-fergusonite transition is reversible and the zircon-scheelite transition nonreversible. From the experiments and the calculations, the room-temperature equation of state for the different phases is also obtained. The anisotropic compressibility of the studied crystal is discussed in terms of the differential compressibility of the Th-O and Ge-O bond

    Thyroid-Associated Orbitopathy and Biomarkers: Where We Are and What We Can Hope for the Future.

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    Thyroid-associated orbitopathy (TAO) is the most common autoimmune disease of the orbit. It occurs more often in patients presenting with hyperthyroidism, characteristic of Graves' disease, but may be associated with hypothyroidism or euthyroidism. The diagnosis of TAO is based on clinical orbital features, radiological criteria, and the potential association with thyroid disease. To date, there is no specific marker of the orbital disease, making the early diagnosis difficult, especially if the orbital involvement precedes the thyroid dysfunction. The goal of this review is to present the disease and combine the available data in the literature concerning investigation of TAO biomarkers. Despite the progress done in the understanding of TAO disease, some important pieces are still missing. Typically, for the future, major efforts have to be done in the discovery of new biomarkers, validation of the suspected candidates on multicenter cohorts with standardized methodologies, and establishment of their clinical performances on the specific clinical application fields in order to improve not only the management of the TAO patients but also the therapeutic options and follow-up

    The long egress of GJ~436b's giant exosphere

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    The M dwarf GJ 436 hosts a transiting warm Neptune known to experience atmospheric escape. Previous observations revealed the presence of a giant hydrogen exosphere transiting the star for more than 5 h, and absorbing up to 56% of the flux in the blue wing of the stellar Lyman-{\alpha} line of neutral hydrogen (H i Ly{\alpha}). The unexpected size of this comet-like exosphere prevented observing the full transit of its tail. In this Letter, we present new Ly{\alpha} observations of GJ 436 obtained with the Space Telescope Imaging Spectrograph (STIS) instrument onboard the Hubble Space Telescope. The stability of the Ly{\alpha} line over six years allowed us to combine these new observations with archival data sets, substantially expanding the coverage of the exospheric transit. Hydrogen atoms in the tail of the exospheric cloud keep occulting the star for 10-25 h after the transit of the planet, remarkably confirming a previous prediction based on 3D numerical simulations with the EVaporating Exoplanet code (EVE). This result strengthens the interpretation that the exosphere of GJ 436b is shaped by both radiative braking and charge exchanges with the stellar wind. We further report flux decreases of 15 +/- 2% and 47 +/- 10% in the red wing of the Ly{\alpha} line and in the line of ionised silicon (Si iii). Despite some temporal variability possibly linked with stellar activity, these two signals occur during the exospheric transit and could be of planetary origin. Follow-up observations will be required to assess the possibility that the redshifted Ly{\alpha} and Si iii absorption signatures arise from interactions between the exospheric flow and the magnetic field of the star.Comment: 10 pages, 7 figures, published in A&

    Translation Invariance, Commutation Relations and Ultraviolet/Infrared Mixing

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    We show that the Ultraviolet/Infrared mixing of noncommutative field theories with the Gronewold-Moyal product, whereby some (but not all) ultraviolet divergences become infrared, is a generic feature of translationally invariant associative products. We find, with an explicit calculation that the phase appearing in the nonplanar diagrams is the one given by the commutator of the coordinates, the semiclassical Poisson structure of the non commutative spacetime. We do this with an explicit calculation for represented generic products.Comment: 24 pages, 1 figur

    Anomalies in noncommutative gauge theories, Seiberg-Witten transformation and Ramond-Ramond couplings

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    We propose an exact expression for the unintegrated form of the star gauge invariant axial anomaly in an arbitrary even dimensional gauge theory. The proposal is based on the inverse Seiberg-Witten map and identities related to it, obtained earlier by comparing Ramond-Ramond couplings in different decsriptions. The integrated anomalies are expressed in terms of a simplified version of the Elliott formula involving the noncommutative Chern character. These anomalies, under the Seiberg-Witten transformation, reduce to the ordinary axial anomalies. Compatibility with existing results of anomalies in noncommutative theories is established.Comment: 16 pages. LaTe

    High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS

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    We report the detection of far-infrared (FIR) CO rotational emission from nearby active galactic nuclei (AGN) and starburst galaxies, as well as several merging systems and Ultra-Luminous Infrared Galaxies (ULIRGs). Using Herschel-PACS, we have detected transitions in the Jupp_{upp} = 14 - 20 range (λ\lambda \sim 130 - 185 μ\mum, ν\nu \sim 1612 - 2300 GHz) with upper limits on (and in two cases, detections of) CO line fluxes up to Jupp_{upp} = 30. The PACS CO data obtained here provide the first well-sampled FIR extragalactic CO SLEDs for this range, and will be an essential reference for future high redshift studies. We find a large range in the overall SLED shape, even amongst galaxies of similar type, demonstrating the uncertainties in relying solely on high-J CO diagnostics to characterize the excitation source of a galaxy. Combining our data with low-J line intensities taken from the literature, we present a CO ratio-ratio diagram and discuss its potential diagnostic value in distinguishing excitation sources and physical properties of the molecular gas. The position of a galaxy on such a diagram is less a signature of its excitation mechanism, than an indicator of the presence (or absence) of warm, dense molecular gas. We then quantitatively analyze the CO emission from a subset of the detected sources with Large Velocity Gradient (LVG) radiative transfer models to fit the CO SLEDs. Using both single-component and two-component LVG models to fit the kinetic temperature, velocity gradient, number density and column density of the gas, we derive the molecular gas mass and the corresponding CO-to-H2_2 conversion factor, αCO\alpha_{CO}, for each respective source. For the ULIRGs we find α\alpha values in the canonical range 0.4 - 5 M_\odot/(K kms1^{-1}pc2^2), while for the other objects, α\alpha varies between 0.2 and 14.} Finally, we compare our best-fit LVG model ..Comment: 39 pages, 3 figures; Accepted to Ap
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