900 research outputs found

    First ALMA maps of HCO, an important precursor of complex organic molecules, towards IRAS 16293-2422

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    The formyl radical HCO has been proposed as the basic precursor of many complex organic molecules such as methanol (CH3_3OH) or glycolaldehyde (CH2_2OHCHO). Using ALMA, we have mapped, for the first time at high angular resolution (\sim1^{\prime\prime}, \sim140 au), HCO towards the Solar-type protostellar binary IRAS 16293-2422, where numerous complex organic molecules have been previously detected. We also detected several lines of the chemically related species H2_2CO, CH3_3OH and CH2_2OHCHO. The observations revealed compact HCO emission arising from the two protostars. The line profiles also show redshifted absorption produced by foreground material of the circumbinary envelope that is infalling towards the protostars. Additionally, IRAM 30m single-dish data revealed a more extended HCO component arising from the common circumbinary envelope. The comparison between the observed molecular abundances and our chemical model suggests that whereas the extended HCO from the envelope can be formed via gas-phase reactions during the cold collapse of the natal core, the HCO in the hot corinos surrounding the protostars is predominantly formed by the hydrogenation of CO on the surface of dust grains and subsequent thermal desorption during the protostellar phase. The derived abundance of HCO in the dust grains is high enough to produce efficiently more complex species such as H2_2CO, CH3_3OH, and CH2_2OHCHO by surface chemistry. We found that the main formation route of CH2_2OHCHO is the reaction between HCO and CH2_2OH.Comment: Accepted in Monthly Notices of the Royal Astronomical Society; 19 pages, 12 figures, 7 table

    Universal amplitude ratios of two-dimensional percolation from field theory

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    We complete the determination of the universal amplitude ratios of two-dimensional percolation within the two-kink approximation of the form factor approach. For the cluster size ratio, which has for a long time been elusive both theoretically and numerically, we obtain the value 160.2, in good agreement with the lattice estimate 162.5 +/- 2 of Jensen and Ziff.Comment: 8 page

    A Single-centre, Before-After Study of the Short- and Long-term Efficacy of Narivent® in the Treatment of Nasal Congestion

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    Objective:Nasal congestion is a common symptom in allergic and nonallergic rhinitis, rhinosinusitis and nasal polyposis. The present study evaluated the clinical effectiveness of Narivent®, an osmo..

    Economic aspects in the management of diabetes in Italy

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    Background: Diabetes mellitus (DM) is a chronic- degenerative disease associated with a high risk of chronic complications and comorbidities. The aim of this study is to estimate the average annual cost incurred by the Italian National Health Service (NHS) for the treatment of DM stratified by patients’ comorbidities. Moreover, the model estimates the economic impact of implementing good clinical practice for the management of patients with DM. Methods: Data were extrapolated from administrative database of the Marche Region and specific inclusion and exclusion criteria were developed from a clinical board in order to estimate patients with DM only, DM+1, DM+2, DM+3 and DM+4 comorbidities (cardiovascular disease, neuropathy, nephropathy and retinopathy). Regional data were considered a good proxy for implementing a previously developed cost-of- illness (COI) model from Italian NHS perspective already published. A scenario analysis was considered to estimate the economic impact of good clinical practice implementation in the treatment of DM and its comorbidities in Italy. Results: The model estimated an average number of patients with DM per year in the Marche region of 85.909 (5.5% of population) from 2008 to 2011. The mean costs per patients with DM only, DM+1, DM+2, DM+3 and DM+4 comorbidities were €341, €1,335, €2,287, €5,231 and €7,085 respectively. From the Italian NHS perspective, the total economic burden of DM in Italy amounted to €8.1. billion/year (22% for drugs, 74% for hospitalization and 4% for visits). Scenario analysis demonstrates that the implementation of good clinical practice could save over €700 million per year. Conclusions: This model is the first study that considers real world data and COI model to estimate the economic burden of DM and its comorbidities from the Italian NHS perspective. Integrated management of the patients with DM could be a good driver for the reduction of the costs of this disease in Italy

    Multiple plasmon resonances in naturally-occurring multiwall nanotubes: infrared spectra of chrysotile asbestos

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    Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of Mg3Si2O5(OH)4Mg_3 Si_2 O_5 (OH)_4. We show by experiment and theory that the infrared spectrum of chrysotile presents multiple plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.Comment: 4 pages, 5 figures. Revtex4 compuscript. Misprint in Eq.(6) correcte

    Deuteration around the ultracompact HII region Mon R2

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    The massive star-forming region Mon R2 hosts the closest ultra-compact HII region that can be spatially resolved with current single-dish telescopes. We used the IRAM-30m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2), in order to studying the chemistry of deuterated molecules toward Mon R2. We found a rich chemistry of deuterated species at both positions, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and isotopologs. Our high spectral resolution observations allowed us to resolve three velocity components: the component at 10 km/s is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12 km/s is found toward the IF position and seems related to the molecular gas; finally, a component at 8.5 km/s is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of all the species, and determined the deuterium fractions (Dfrac). The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+ which have values 10 times lower. The values found in Mon R2 are well explained with pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the [H13CN]/[HN13C] ratio is very high (~11) for the 10 km/s component, which also agree with our model predictions for an age of ~0.01-0.1 Myr. The deuterium chemistry is a good tool for studying star-forming regions. The low-mass star-forming regions seem well characterized with Dfrac(N2H+) or Dfrac(HCO+), but it is required a complete chemical modeling to date massive star-forming regions, because the higher gas temperature together with the rapid evolution of massive protostars.Comment: 14 pages of manuscript, 17 pages of apendix, 7 figures in the main text, accepted for publication in A&

    Spatial distribution of small hydrocarbons in the neighborhood of the Ultra Compact HII region Monoceros R2

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    We study the chemistry of small hydrocarbons in the photon-dominated regions (PDRs) associated with the ultra-compact HII region Mon R2. Our goal is to determine the variations of the abundance of small hydrocarbons in a high-UV irradiated PDR and investigate their chemistry. We present an observational study of CH, CCH and c-C3_3H2_2 in Mon R2 combining data obtained with the IRAM 30m telescope and Herschel. We determine the column densities of these species, and compare their spatial distributions with that of polycyclic aromatic hydrocarbon (PAH). We compare the observational results with different chemical models to explore the relative importance of gas-phase, grain-surface and time-dependent chemistry in these environments. The emission of the small hydrocarbons show different patterns. The CCH emission is extended while CH and c-C3_3H2_2 are concentrated towards the more illuminated layers of the PDR. The ratio of the column densities of c-C3_3H2_2 and CCH shows spatial variations up to a factor of a few, increasing from N(cCN(c-C_3HH_2)/N(CCH)0.004)/N(CCH)\approx0.004 in the envelope to a maximum of 0.0150.029\sim0.015-0.029 towards the 8μ\mum emission peak. Comparing these results with other galactic PDRs, we find that the abundance of CCH is quite constant over a wide range of G0_0, whereas the abundance of c-C3_3H2_2 is higher in low-UV PDRs. In Mon R2, the gas-phase steady-state chemistry can account relatively well for the abundances of CH and CCH in the most exposed layers of the PDR, but falls short by a factor of 10 to reproduce c-C3_3H2_2. In the molecular envelope, time-dependent effects and grain surface chemistry play a dominant role in determining the hydrocarbons abundances. Our study shows that CCH and c-C3_3H2_2 present a complex chemistry in which UV photons, grain-surface chemistry and time dependent effects contribute to determine their abundances.Comment: 18 pages, 11 figures, 7 tables. Proposed for acceptance in A&A. Abstract abridge

    Comparison between direct measurements and indirect estimations of hydraulic conductivity for slope deposits of the North-Western Tuscany, Italy

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    Hydraulic conductivity (K) is a relevant engineering geology property of deposits that cover the geological bedrock (Slope Deposits – SD). This parameter is useful for many applications fields such as: simulations of both infiltration and runoff processes, hillslope stability numerical analysis, hydrological studies, soil science and environmental problems. A wide range of methods are available in the literature in order to estimate K. Anyhow, they can be divided into direct measurement (field and laboratory test) and indirect estimations (eg. correlation from grain size, pedotransfer functions). However, many factors (eg. SD grain size, bulk density, organic matter, etc.) can affect the K value hence the determination of K within SD is often a challenge. Moreover, the value of K generally shows an high spatial variability requiring a large number of direct measurements to obtain robust spatial estimations. Indirect methods may be used alternatively or in pair with direct methods. However, relations between K and other soil physical properties are generally suitable only for specific type of soils, therefore, the application of those relations are constrained. In this work a wide (about 200) set of field measurements were performed in North-Western Tuscany in order to assess the variability of K in the vadose zone for SD characterized by different grain size composition. Measurements were carried out by means of both constant and falling head permeameters, as well as double ring infiltrometer. In the test sites engineering geology properties of SD such as bulk density and depth have been collected, moreover, samples have been collected for laboratory analysis. A statistical analysis of the K value has been performed for SD characterized by different grain size distribution and geological bedrock. Moreover, a comparison between the field methods have been also performed. Finally, a comparison between measured and estimated values of K has been done in order to assess the reliability of different equations to predict K. The results show that the K value varies across: different geological settings, the SD profile and the geographic neighborhood of the test site. Moreover, the results highlight that the indirect methods used in this work have to be used carefully in our study area

    Class I methanol masers in low-mass star formation regions

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    Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, rotational diagram analysis showed that the latter source is also a maser. The main properties of the newly detected masers are similar to those of Class I methanol masers in regions of massive star formation. The former masers are likely to be an extension of the latter maser population toward low luminosities of both the masers and the corresponding YSOs.Comment: 5 pages, 1 figure, Proc. IAU Symp. 287 "Cosmic Masers: from OH to H0". LSR velocities of the HH25 masers, which are presented in Table 1, are correcte

    Ion diffusion modelling of Fricke-agarose dosemeter gels

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    In Fricke-agarose gels, an accurate determination of the spatial dose distribution is hindered by the diffusion of ferric ions. In this work, a model was developed to describe the diffusion process within gel samples of finite length and, thus, permit the reconstruction of the initial spatial distribution of the ferric ions. The temporal evolution of the ion concentration as a function of the initial concentration is derived by solving Fick's second law of diffusion in two dimensions with boundary reflections. The model was applied to magnetic resonance imaging data acquired at high spatial resolution (0.3 mm) and was found to describe accurately the observed diffusion effect
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