2,371 research outputs found
Synthetic synchrotron emission maps from MHD models for the jet of M87
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- variations from the 11 Gyr-old host star Kepler-444: a planetary origin ?
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- 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- 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
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
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
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.
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
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
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
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
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 J = 14 - 20 range
( 130 - 185 m, 1612 - 2300 GHz) with upper limits
on (and in two cases, detections of) CO line fluxes up to J = 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-H conversion factor, , for each
respective source. For the ULIRGs we find values in the canonical
range 0.4 - 5 M/(K kmspc), while for the other objects,
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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