611 research outputs found

    Railroads and the Marketplace

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    Internationalisation of SMEs:a micro-economic approach

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    Internationalisation can be crucial to the long-term success of small- to mediumsized businesses, especially since they are expected to show international growth at an early stage. Our research explores whether firms using an opportunistic portfolio approach are more successful in their efforts to internationalise than are firms using the stage and network approaches. Our research may be characterized as a multi-company longitudinal clinical case study using triangulation to analyse data. The sample consists of six Nordic business-to-business, high-technology firms with sales of €100,000 to €10 million. Four of the six firms had significant revenue from the food industry, petrochemicals, pharmaceuticals, bulk and speciality chemicals and the pulp and paper industry. The results indicate that the opportunistic portfolio model provides some explanation of how firms can internationalise successfully

    Exploring DCO+^+ as a tracer of thermal inversion in the disk around the Herbig Ae star HD163296

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    We aim to reproduce the DCO+^+ emission in the disk around HD163296 using a simple 2D chemical model for the formation of DCO+^+ through the cold deuteration channel and a parametric treatment of the warm deuteration channel. We use data from ALMA in band 6 to obtain a resolved spectral imaging data cube of the DCO+^+ JJ=3--2 line in HD163296 with a synthesized beam of 0."53×\times 0."42. We adopt a physical structure of the disk from the literature that reproduces the spectral energy distribution. We then apply a simplified chemical network for the formation of DCO+^+ that uses the physical structure of the disk as parameters along with a CO abundance profile, a constant HD abundance and a constant ionization rate. Finally, from the resulting DCO+^+ abundances, we calculate the non-LTE emission using the 3D radiative transfer code LIME. The observed DCO+^+ emission is reproduced by a model with cold deuteration producing abundances up to 1.6×10111.6\times 10^{-11}. Warm deuteration, at a constant abundance of 3.2×10123.2\times 10^{-12}, becomes fully effective below 32 K and tapers off at higher temperatures, reproducing the lack of DCO+^+ inside 90 AU. Throughout the DCO+^+ emitting zone a CO abundance of 2×1072\times 10^{-7} is found, with \sim99\% of it frozen out below 19 K. At radii where both cold and warm deuteration are active, warm deuteration contributes up to 20\% of DCO+^+, consistent with detailed chemical models. The decrease of DCO+^+ at large radii is attributed to a temperature inversion at 250 AU, which raises temperatures above values where cold deuteration operates. Increased photodesorption may also limit the radial extent of DCO+^+. The corresponding return of the DCO+^+ layer to the midplane, together with a radially increasing ionization fraction, reproduces the local DCO+^+ emission maximum at \sim260 AU.Comment: 9 pages, 5 figures, accepted 7th July 201

    A Disk-based Dynamical Mass Estimate for the Young Binary AK Sco

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    We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust in the disk orbiting the pre-main sequence binary AK Sco. By forward-modeling the disk velocity field traced by CO J=2-1 line emission, we infer the mass of the central binary, M=2.49±0.10 MM_\ast = 2.49 \pm 0.10~M_\odot, a new dynamical measurement that is independent of stellar evolutionary models. Assuming the disk and binary are co-planar within \sim2{\deg}, this disk-based binary mass measurement is in excellent agreement with constraints from radial velocity monitoring of the combined stellar spectra. These ALMA results are also compared with the standard approach of estimating masses from the location of the binary in the Hertzsprung-Russell diagram, using several common pre-main sequence model grids. These models predict stellar masses that are marginally consistent with our dynamical measurement (at 2σ\sim 2\,\sigma), but are systematically high (by \sim10%). These same models consistently predict an age of 18±118\pm1 Myr for AK Sco, in line with its membership in the Upper Centaurus-Lupus association but surprisingly old for it to still host a gas-rich disk. As ALMA accumulates comparable data for large samples of pre-main sequence stars, the methodology employed here to extract a dynamical mass from the disk rotation curve should prove extraordinarily useful for efforts to characterize the fundamental parameters of early stellar evolution.Comment: Accepted to The Astrophysical Journa

    DCO+^+, DCN and N2_2D+^+ reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296

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    The formation pathways of deuterated species trace different regions of protoplanetary disks and may shed light into their physical structure. We aim to constrain the radial extent of main deuterated species; we are particularly interested in spatially characterizing the high and low temperature pathways for enhancing deuteration of these species. We observed the disk surrounding the Herbig Ae star HD 163296 using ALMA in Band 6 and obtained resolved spectral imaging data of DCO+^+ (JJ=3-2), DCN (JJ=3-2) and N2_2D+^+ (JJ=3-2). We model the radial emission profiles of DCO+^+, DCN and N2_2D+^+, assuming their emission is optically thin, using a parametric model of their abundances and radial excitation temperature estimates. DCO+^+ can be described by a three-region model, with constant-abundance rings centered at 70 AU, 150 AU and 260 AU. The DCN radial profile peaks at about ~60 AU and N2_2D+^+ is seen in a ring at ~160 AU. Simple models of both molecules using constant abundances reproduce the data. Assuming reasonable average excitation temperatures for the whole disk, their disk-averaged column densities (and deuterium fractionation ratios) are 1.6-2.6×1012\times 10^{12} cm2^{-2} (0.04-0.07), 2.9-5.2×1012\times 10^{12} cm2^{-2} (\sim0.02) and 1.6-2.5 ×1011\times 10^{11} cm2^{-2} (0.34-0.45) for DCO+^+, DCN and N2_2D+^+, respectively. Our simple best-fit models show a correlation between the radial location of the first two rings in DCO+^+ and the DCN and N2_2D+^+ abundance distributions that can be interpreted as the high and low temperature deuteration pathways regimes. The origin of the third DCO+^+ ring at 260 AU is unknown but may be due to a local decrease of ultraviolet opacity allowing the photodesorption of CO or due to thermal desorption of CO as a consequence of radial drift and settlement of dust grains

    Increased H2_2CO production in the outer disk around HD 163296

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    Three formaldehyde lines were observed (H2_2CO 303_{03}--202_{02}, H2_2CO 322_{22}--221_{21}, and H2_2CO 321_{21}--220_{20}) in the protoplanetary disk around the Herbig Ae star HD 163296 with ALMA at 0.5 arcsecond (60 AU) spatial resolution. H2_2CO 303_{03}--202_{02} was readily detected via imaging, while the weaker H2_2CO 322_{22}--221_{21} and H2_2CO 321_{21}--220_{20} lines required matched filter analysis to detect. H2_2CO is present throughout most of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of the H2_2CO emission is likely caused by an optically thick dust continuum. The H2_2CO radial intensity profile shows a peak at 100 AU and a secondary bump at around 300 AU, suggesting increased production in the outer disk. Different parameterizations of the H2_2CO abundance were compared to the observed visibilities with χ2\chi^2 minimization, using either a characteristic temperature, a characteristic radius or a radial power law index to describe the H2_2CO chemistry. Similar models were applied to ALMA Science Verification data of C18^{18}O. In all modeling scenarios, fits to the H2_2CO data show an increased abundance in the outer disk. The overall best-fit H2_2CO model shows a factor of two enhancement beyond a radius of 270±\pm20 AU, with an inner abundance of 2 ⁣ ⁣5×10122\!-\!5 \times 10^{-12}. The H2_2CO emitting region has a lower limit on the kinetic temperature of T>20T > 20 K. The C18^{18}O modeling suggests an order of magnitude depletion in the outer disk and an abundance of 4 ⁣ ⁣12×1084\!-\!12 \times 10^{-8} in the inner disk. The increase in H2_2CO outer disk emission could be a result of hydrogenation of CO ices on dust grains that are then sublimated via thermal desorption or UV photodesorption, or more efficient gas-phase production beyond about 300 AU if CO is photodisocciated in this region

    Using Protoplanetary Disks To Weigh The Youngest Stars And Constrain The Earliest Stages Of Stellar Evolution

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    Mass is the fundamental property that determines the fate of a star. In particular, the masses of young stars are of great relevance to many astrophysical problems, including star and planet formation. We have developed a novel approach that combines spatially resolved sub-millimeter spectral line imaging and optical/near-infrared high resolution spectroscopy to derive the fundamental properties of a young star: mass, temperature, and radius. By applying our technique to a sample of pre-main sequence stars, we are mapping out a dynamically-calibrated Hertzsprung-Russell diagram for the express purpose of evaluating pre-main sequence evolutionary models. Looking forward, ALMA is poised to deliver precise stellar masses in statistically large quantities, enabling a meaningful survey of the fundamental properties of young stars

    A disk-based dynamical mass estimate for the young binary AK Sco

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    Funding: I.C. is supported by the NSF Graduate Fellowship and the Smithsonian Institution.We present spatially and spectrally resolved Atacama Large Millimeter / submillimeter Array (ALMA) observations of gas and dust in the disk orbiting the pre-main sequence (pre-MS) binary AK Sco. By forward-modeling the disk velocity field traced by CO J = 2–1 line emission, we infer the mass of the central binary, M* = 2.49 ± 0.10 M⊙, a new dynamical measurement that is independent of stellar evolutionary models. Assuming the disk and binary are co-planar within ∼2°, this disk-based binary mass measurement is in excellent agreement with constraints from radial velocity monitoring of the combined stellar spectra. These ALMA results are also compared with the standard approach of estimating masses from the location of the binary in the Hertzsprung–Russell diagram, using several common pre-MS model grids. These models predict stellar masses that are marginally consistent with our dynamical measurement (at ∼2σ), but are systematically high (by ∼10%). These same models consistently predict an age of 18 ± 1 Myr for AK Sco, in line with its membership in the Upper Centaurus–Lupus association but surprisingly old for it to still host a gas-rich disk. As ALMA accumulates comparable data for large samples of pre-MS stars, the methodology employed here to extract a dynamical mass from the disk rotation curve should prove extraordinarily useful for efforts to characterize the fundamental parameters of early stellar evolution.Peer reviewe
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