336 research outputs found

    Advanced Microwave Precipitation Radiometer (AMPR) for remote observation of precipitation

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    The design, development, and tests of the Advanced Microwave Precipitation Radiometer (AMPR) operating in the 10 to 85 GHz range specifically for precipitation retrieval and mesoscale storm system studies from a high altitude aircraft platform (i.e., ER-2) are described. The primary goals of AMPR are the exploitation of the scattering signal of precipitation at frequencies near 10, 19, 37, and 85 GHz together to unambiguously retrieve precipitation and storm structure and intensity information in support of proposed and planned space sensors in geostationary and low earth orbit, as well as storm-related field experiments. The development of AMPR will have an important impact on the interpretation of microwave radiances for rain retrievals over both land and ocean for the following reasons: (1) A scanning instrument, such as AMPR, will allow the unambiguous detection and analysis of features in two dimensional space, allowing an improved interpretation of signals in terms of cloud features, and microphysical and radiative processes; (2) AMPR will offer more accurate comparisons with ground-based radar data by feature matching since the navigation of the ER-2 platform can be expected to drift 3 to 4 km per hour of flight time; and (3) AMPR will allow underflights of the SSM/I satellite instrument with enough spatial coverage at the same frequencies to make meaningful comparisons of the data for precipitation studies

    An original interferometric study of NGC 1068 with VISIR BURST mode images

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    We present 12.8 microns images of the core of NGC 1068 obtained with the BURST mode of the VLT/VISIR. We trace structures under the diffraction limit of one UT and we investigate the link between dust in the vicinity of the central engine of NGC 1068, recently resolved by interferometry with MIDI, and more extended structures. This step is mandatory for a multi-scale understanding of the sources of mid-infrared emission in AGNs. A speckle processing of VISIR BURST mode images was performed to extract very low spatial-frequency visibilities, first considering the full field of VISIR BURST mode images and then limiting it to the mask used for the acquisition of MIDI data. Extracted visibilities are reproduced with a multi-component model. We identify two major sources of emission: one compact < 85 mas, associated with the dusty torus, and an elliptical one, (< 140) mas x 1187 mas at P.A.=-4 degrees from N to E. This is consistent with previous deconvolution processes. The combination with MIDI data reveals the close environment of the dusty torus to contribute to about 83 percent of the MIR flux seen by MIDI. This strong contribution has to be considered in modeling long baseline interferometric data. It must be related to the NS elongated component which is thought to originate from individually unresolved dusty clouds and is located inside the ionization cone. Low temperatures of the dusty torus are not challenged, emphasizing the scenarios of clumpy torus.Comment: 10 pages, 7 figures, accepted for publication in A&

    Birth and death processes with absorption

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    Spectral measures and transition probabilities of birth and death processes with λ0=μ0=0 are obtained as limite when λ0→0+ of the corresponding quantities. In particular the case of finite population is discussed in full detail. Pure birth and death processes are used to derive an inequality for Dirichlet polynomials

    A Multi-Wavelength Infrared Study of NGC 891

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    We present a multi-wavlength infrared study of the nearby, edge-on, spiral galaxy NGC 891. We have examined 20 independent, spatially resolved IR images of this galaxy, 14 of which are newly reduced and/or previously unpublished images. These images span a wavelength regime from 1.2 microns in which the emission is dominated by cool stars, through the MIR, in which emission is dominated by PAHs, to 850 microns, in which emission is dominated by cold dust in thermal equilibrium with the radiation field. The changing morphology of the galaxy with wavelength illustrates the changing dominant components. We detect extra-planar dust emission in this galaxy, consistent with previously published results, but now show that PAH emission is also in the halo, to a vertical distance of z >= 2.5 kpc. We compare the vertical extents of various components and find that the PAHs (from 7.7 and 8 micron data) and warm dust (24 microns) extend to smaller z heights than the cool dust (450 microns). For six locations in the galaxy for which the S/N was sufficient, we present SEDs of the IR emission, including two in the halo - the first time a halo SED in an external galaxy has been presented. We have modeled these SEDs and find that the PAH fraction is similar to Galactic values (within a factor of two), with the lowest value at the galaxy's center, consistent with independent results of other galaxies. In the halo environment, the fraction of dust exposed to a colder radiation field, is of order unity, consistent with an environment in which there is no star formation. The source of excitation is likely from photons escaping from the disk.Comment: 24 pages, 17 figures, 7 tables, accepted for publication in MNRA

    The effects of star formation on the low-metallicity ISM: NGC4214 mapped with Herschel/PACS spectroscopy

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    We present Herschel/PACS spectroscopic maps of the dwarf galaxy NC4214 observed in 6 far infrared fine-structure lines: [C II] 158mu, [O III] 88mu, [O I] 63mu, [O I] 146mu, [N II] 122mu, and [N II] 205mu. The maps are sampled to the full telescope spatial resolution and reveal unprecedented detail on ~ 150 pc size scales. We detect [C II] emission over the whole mapped area, [O III] being the most luminous FIR line. The ratio of [O III]/[C II] peaks at about 2 toward the sites of massive star formation, higher than ratios seen in dusty starburst galaxies. The [C II]/CO ratios are 20 000 to 70 000 toward the 2 massive clusters, which are at least an order of magnitude larger than spiral or dusty starbursts, and cannot be reconciled with single-slab PDR models. Toward the 2 massive star-forming regions, we find that L[CII] is 0.5 to 0.8% of the LTIR . All of the lines together contribute up to 2% of LTIR . These extreme findings are a consequence of the lower metallicity and young, massive-star formation commonly found in dwarf galaxies. These conditions promote large-scale photodissociation into the molecular reservoir, which is evident in the FIR line ratios. This illustrates the necessity to move to multiphase models applicable to star-forming clusters or galaxies as a whole.Comment: Accepted for publication in the A&A Herschel Special Issu

    Sustainable approaches for drug repurposing in rare diseases: recommendations from the IRDiRC Task Force

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    Drug repurposing represents a real opportunity to address unmet needs and improve the lives of rare disease patients. It is often presented as a faster, safer and cheaper path for bringing drugs into new indications. However, several economic, regulatory and scientific barriers can impede the successful repurposing of drugs for rare diseases. The International Rare Diseases Research Consortium (IRDiRC) set up the Task Force on Sustainable Models in Drug Repurposing with the objective of identifying key factors for achieving sustainable repurposing approaches in rare diseases. In order to help inform expert opinion, the Task Force investigated six cases of medicinal products repurposed into new rare indications and four cases of ongoing development programs. A questionnaire addressing the major steps of the repurposing approach was developed by the Task Force and sent to contact points of the organizations. In addition, interviews were conducted with the relevant organization representatives to conduct a deeper dive into the sustainability of the repurposing approach for each of the selected cases. Based on the collective experience of the members of the Task Force and the output from the questionnaires/interviews, we have identified ten key factors that should be considered by those embarking on repurposing projects. These factors include the identification of unmet patient needs and partnership with patients, collection of evidence concerning disease prevalence, patient numbers, drug pharmacology and disease etiology, drug industrial property status, off-label or compounding use, data from past clinical studies and needs for extended non-clinical and clinical studies. The development of a collaborative funding framework and early discussion with regulators and payers are additional factors to implement early in the development of sustainable drug repurposing projects

    ALMA Resolves 30 Doradus: Sub-parsec Molecular Cloud Structure Near the Closest Super-Star Cluster

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    We present ALMA observations of 30 Doradus -- the highest resolution view of molecular gas in an extragalactic star formation region to date (~0.4pc x 0.6pc). The 30Dor-10 cloud north of R136 was mapped in 12CO 2-1, 13CO 2-1, C18O 2-1, 1.3mm continuum, the H30alpha recombination line, and two H2CO 3-2 transitions. Most 12CO emission is associated with small filaments and clumps (<1pc, ~1000 Msun at the current resolution). Some clumps are associated with protostars, including "pillars of creation" photoablated by intense radiation from R136. Emission from molecular clouds is often analyzed by decomposition into approximately beam-sized clumps. Such clumps in 30 Doradus follow similar trends in size, linewidth, and surface density to Milky Way clumps. The 30 Doradus clumps have somewhat larger linewidths for a given size than predicted by Larson's scaling relation, consistent with pressure confinement. They extend to higher surface density at a given size and linewidth compared to clouds studied at 10pc resolution. These trends are also true of clumps in Galactic infrared-dark clouds; higher resolution observations of both environments are required. Consistency of clump masses calculated from dust continuum, CO, and the virial theorem reveals that the CO abundance in 30 Doradus clumps is not significantly different from the LMC mean, but the dust abundance may be reduced by ~2. There are no strong trends in clump properties with distance from R136; dense clumps are not strongly affected by the external radiation field, but there is a modest trend towards lower dense clump filling fraction deeper in the cloud.Comment: accepted to Ap

    Spectral characteristics of water megamaser galaxies II: ESO 103-G035, TXS 2226-184, and IC 1481

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    Long-slit optical emission-line spectra of the H2O megamaser galaxies ESO 103-G03, TXS 2226-184, and IC 1481 are evaluated in order to look for characteristics typical for water-megamaser galaxies. We present rotation curves, line ratios, electron densities, temperatures, and Hbeta luminosities. The successful line-profile decompositions rest on d-Lorentzians with an additional parameter d to adjust the wings, rather than Gaussians or Lorentzians as basic functions. No significant velocity gradient is found along the major axis in the innermost 2 kpc of TXS 2226-184. IC 1481 reveals a spectrum suggestive of a vigorous starburst in the central kiloparsec 10^8 years ago. None of the three galaxies shows any hints for outflows nor special features which could give clues to the presence of H2O megamaser emission. The galaxies are of normal Seyfert-2 (ESO 103-G035) or LINER (TXS 2226-184, IC 1481) type.Comment: 12 pages, 14 figures, accepted for publication in A&A, corrected typo

    The small dispersion of the mid IR -- hard X-ray correlation in AGN

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    Context: We investigate mid-infrared and X-ray properties of the dusty torus in unification scenarios for active galactic nuclei. Aims: We use the relation between mid IR and hard X-ray luminosities to constrain AGN unification scenarios. Methods: With VISIR at the VLT, we have obtained the currently highest angular resolution (0".35 FWHM) narrow-band mid infrared images of the nuclei of 8 nearby Seyfert galaxies. Combining these observations with X-ray data from the literature we study the correlation between their mid IR and hard X-ray luminosities. Results: We find that the rest frame 12.3 mircon (L_MIR) and 2-10 keV (L_X) luminosities are correlated at a highly significant level. The best fit power-law to our data is log L_MIR \propto (1.60 \pm 0.22) log L_X, showing a much smaller dispersion than earlier studies. Conclusions: The similarity in the og L_MIR / log L_X ratio between Sy1s and Sy2s even using high angular resolution MIR data implies that the similarity is intrinsic to AGN and not caused by contamination from extra-nuclear emission. This supports clumpy torus models. The exponent of the correlation constrains the inner geometry of the torus.Comment: 5 pages, 3 figures, accepted for publication in Astronomy & Astrophysic

    Bianchi type II,III and V diagonal Einstein metrics re-visited

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    We present, for both minkowskian and euclidean signatures, short derivations of the diagonal Einstein metrics for Bianchi type II, III and V. For the first two cases we show the integrability of the geodesic flow while for the third case a somewhat unusual bifurcation phenomenon takes place: for minkowskian signature elliptic functions are essential in the metric while for euclidean signature only elementary functions appear
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