611 research outputs found
Internationalisation of SMEs:a micro-economic approach
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
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 =3--2 line in HD163296 with a synthesized beam of
0."53 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 .
Warm deuteration, at a constant abundance of , 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 is found, with 99\% 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 260 AU.Comment: 9 pages, 5 figures, accepted 7th July 201
A Disk-based Dynamical Mass Estimate for the Young Binary AK Sco
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, , a new dynamical measurement
that is independent of stellar evolutionary models. Assuming the disk and
binary are co-planar within 2{\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 ), but are
systematically high (by 10%). These same models consistently predict an
age of 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 ND reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296
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 (=3-2), DCN (=3-2) and ND
(=3-2). We model the radial emission profiles of DCO, DCN and
ND, 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
ND 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 cm
(0.04-0.07), 2.9-5.2 cm (0.02) and 1.6-2.5 cm (0.34-0.45) for DCO, DCN and ND, respectively.
Our simple best-fit models show a correlation between the radial location of
the first two rings in DCO and the DCN and ND 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 HCO production in the outer disk around HD 163296
Three formaldehyde lines were observed (HCO 3--2, HCO
3--2, and HCO 3--2) in the protoplanetary disk
around the Herbig Ae star HD 163296 with ALMA at 0.5 arcsecond (60 AU) spatial
resolution. HCO 3--2 was readily detected via imaging, while
the weaker HCO 3--2 and HCO 3--2 lines
required matched filter analysis to detect. HCO is present throughout most
of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of
the HCO emission is likely caused by an optically thick dust continuum. The
HCO 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 HCO abundance were compared to the observed
visibilities with minimization, using either a characteristic
temperature, a characteristic radius or a radial power law index to describe
the HCO chemistry. Similar models were applied to ALMA Science Verification
data of CO. In all modeling scenarios, fits to the HCO data show an
increased abundance in the outer disk. The overall best-fit HCO model shows
a factor of two enhancement beyond a radius of 27020 AU, with an inner
abundance of . The HCO emitting region has a lower
limit on the kinetic temperature of K. The CO modeling suggests
an order of magnitude depletion in the outer disk and an abundance of in the inner disk. The increase in HCO 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
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
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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