793 research outputs found
Industry Evolution Through Consolidation: Implications for Addiction Treatment.
Drawing on experiences in other industries, this article argues that the business of addiction treatment is likely to be transformed by the advent of a period of consolidation, in which a number of small independent programs will be acquired by larger, better capitalized, and managerially more sophisticated enterprises. Consolidation will be driven by opportunities to leverage new technologies, to exploit new regulatory initiatives, and to introduce economies of scale and scope into an industry that is currently highly fragmented. The process is likely to result in segmentation of the market, with the coexistence of large, generalist, highly standardized firms and a number of small highly specialized firms. When an industry consolidates, the types and quality of services provided can improve through the adoption of best practices and through increased competition among larger providers. If these larger providers are publicly traded, however, efforts to improve will inevitably be influenced by pressures to maintain or increase quarter-to-quarter earnings and share prices, leaving open the long-term impact on service quality
Structure of the outer Galactic disc with Gaia-DR2
AIMS. We calculate the stellar density using star counts obtained from Gaia
DR2 up to a Galactocentric distance R=20 kpc with a deconvolution technique for
the parallax errors. Then we analyse the density in order to study the
structure of the outer Galactic disc, mainly the warp.
METHODS. In order to carry out the deconvolution, we used the Lucy inversion
technique for recovering the corrected star counts. We also used the Gaia
luminosity function of stars with to extract the stellar density from
the star counts.
RESULTS. The stellar density maps can be fitted by an exponential disc in the
radial direction kpc, with a weak dependence on the azimuth,
extended up to 20 kpc without any cut-off. The flare and warp are clearly
visible. The best fit of a symmetrical S-shaped warp gives pc for the whole population. When we
analyse the northern and southern warps separately, we obtain an asymmetry of
an larger amplitude in the north. This result may be influenced by
extinction because the Gaia G band is quite prone to extinction biases.
However, we tested the accuracy of the extinction map we used, which shows that
the extinction is determined very well in the outer disc. Nevertheless, we
recall that we do not know the full extinction error, and neither do we know
the systematic error of the map, which may influence the final result.
The analysis was also carried out for very luminous stars alone (),
which on average represents a younger population. We obtain similar
scale-length values, while the maximum amplitude of the warp is
larger than with the whole population. The north-south asymmetry is maintained.Comment: 19 pages, 21 figures, accepted to be published in A&
Probability distribution of density fluctuations in the non-linear regime
We present a general procedure for obtaining the present density fluctuation
probability distribution given the statistics of the initial conditions. The
main difficulties faced with regard to this problem are those related to the
non-linear evolution of the density fluctuations and those posed by the fact
that the fields we are interested in are the result of filtering an underlying
field with structure down to scales much smaller than that of filtering. The
solution to the latter problem is discussed here in detail and the solution to
the former is taken from a previous work.
We have checked the procedure for values of the rms density fluctuation as
large as 3/2 and several power spectra and found that it leads to results in
excellent agreement with those obtained in numerical simulations. We also
recover all available exact results from perturbation theory.Comment: Accepted to be published in Ap
A three-dimensional Galactic extinction model
A large-scale three-dimensional model of Galactic extinction is presented
based on the Galactic dust distribution model of Drimmel and Spergel (2001).
The extinction A_V to any point within the Galactic disk can be quickly deduced
using a set of three-dimensional cartesian grids. Extinctions from the model
are compared to empirical extinction measures, including lines-of-sight in and
near the Galactic plane using optical and NIR extinction measures; in
particular we show how extinction can be derived from NIR color-magnitude
diagrams in the Galactic plane to a distance of 8 kiloparsec.Comment: 12 pages, to be published in A&
Virial theorem in clusters of galaxies with MOND
A specific modification of Newtonian dynamics known as MOND has been shown to
reproduce the dynamics of most astrophysical systems at different scales
without invoking non-baryonic dark matter (DM). There is, however, a
long-standing unsolved problem when MOND is applied to rich clusters of
galaxies in the form of a deficit (by a factor around two) of predicted
dynamical mass derived from the virial theorem with respect to observations. In
this article we approach the virial theorem using the velocity dispersion of
cluster members along the line of sight rather than using the cluster
temperature from X-ray data and hydrostatic equilibrium. Analytical
calculations of the virial theorem in clusters for Newtonian gravity+DM and
MOND are developed, applying pressure (surface) corrections for non-closed
systems. Recent calibrations of DM profiles, baryonic ratio and baryonic
( model or others) profiles are used, while allowing free parameters to
range within the observational constraints. It is shown that solutions exist
for MOND in clusters that give similar results to Newton+DM -- particularly in
the case of an isothermal model for and core radii
between 0.1 and 0.3 times (in agreement with the known data).
The disagreements found in previous studies seem to be due to the lack of
pressure corrections (based on inappropriate hydrostatic equilibrium
assumptions) and/or inappropriate parameters for the baryonic matter profiles.Comment: accepted to be published in MNRA
Genetic Transformation of Quercus ilex Somatic Embryos with a Gnk2-like Protein That Reveals a Putative Anti-Oomycete Action
Holm oak is a key tree species in Mediterranean ecosystems, whose populations have
been increasingly threatened by oak decline syndrome, a disease caused by the combined action of
Phytophthora cinnamomi and abiotic stresses. The aim of the present study was to produce holm oak
plants that overexpress the Ginkbilobin-2 homologous domain gene (Cast_Gnk2-like) that it is known
to possess antifungal properties. Proembryogenic masses (PEMs) isolated from four embryogenic
lines (Q8, E2, Q10-16 and E00) were used as target explants. PEMs were co-cultured for 5 days with
Agrobacterium EHA105pGnk2 and then cultured on selective medium containing kanamycin (kan)
and carbenicillin. After 14 weeks on selective medium, the transformation events were observed in
somatic embryos of lines Q8 and E2 and a total of 4 transgenic lines were achieved. The presence of the
Cast_Gnk2-like gene on transgenic embryos was verified by PCR, and the number of transgene copies
and gene expression was estimated by qPCR. Transgenic plants were obtained from all transgenic
lines after cold storage of the somatic embryos for 2 months and subsequent transfer to germination
medium. In an in vitro tolerance assay with the pathogen P. cinnamomi, we observed that transgenic
plants were able to survive longer than wild typeinfo:eu-repo/semantics/publishedVersio
A major star formation region in the receding tip of the stellar Galactic bar. II. Supplementary information and evidence that the bar is not the same structure as the triaxial bulge previouly reported
This paper is the second part of Garzon et al. (1997: ApJ 491, L31) in which
we presented an outline of the analysis of 60 spectra from a follow-up program
to the Two Micron Galactic Survey (TMGS) project in the l=27 deg., b=0 deg.
area. In this second part, we present a more detailed explanation of the
analysis as well a library of the spectra for more complete information for
each of the 60 stars, and further discussions on the implications for the
structure of the Galaxy.
This region contains a prominent excess in the flux distribution and star
counts previously observed in several spectral ranges, notably in the TMGS.
More than 50% of the spectra of the stars detected with m_K<5.0 mag, within a
very high confidence level, correspond to stars of luminosity class I, and a
significant proportion of the remainder are very late giants which must also be
rapidly evolving. We make the case, using all the available evidence, that we
are observing a region at the nearer end of the Galactic bar, where the Scutum
spiral arm breaks away, and that this is powerful evidence for the presence of
the bar. Alternative explanations do not give nearly such a satisfactory
account of the observations.
The space localization of one and, a fortiori, of both ends of the bar allows
us to infer a position angle for the bar of around 75 deg. with respect to the
Sun-Galactic centre line. The angle is different from that given by other
authors for the bar and this, we think, is because they refer to the triaxial
bulge and not to the bar as detected here.Comment: 21 pages, 1 table, 9 figures, accepted in A
First Report of CRISPR/Cas9 Gene Editing in Castanea sativa Mill
CRISPR/Cas9 has emerged as the most important tool for genome engineering due to its simplicity, design flexibility, and high efficiency. This technology makes it possible to induce point mutations in one or some target sequences simultaneously, as well as to introduce new genetic variants by homology-directed recombination. However, this approach remains largely unexplored in forest species. In this study, we reported the first example of CRISPR/Cas9-mediated gene editing in Castanea genus. As a proof of concept, we targeted the gene encoding phytoene desaturase (pds), whose mutation disrupts chlorophyll biosynthesis allowing for the visual assessment of knockout efficiency. Globular and early torpedo-stage somatic embryos of Castanea sativa (European chestnut) were cocultured for 5 days with a CRISPR/Cas9 construct targeting two conserved gene regions of pds and subsequently cultured on a selection medium with kanamycin. After 8 weeks of subculture on selection medium, four kanamycin-resistant embryogenetic lines were isolated. Genotyping of these lines through target Sanger sequencing of amplicons revealed successful gene editing. Cotyledonary somatic embryos were maturated on maltose 3% and cold-stored at 4°C for 2 months. Subsequently, embryos were subjected to the germination process to produce albino plants. This study opens the way to the use of the CRISPR/Cas9 system in European chestnut for biotechnological application
Near-infrared and optical observations of galactic warps: A common, unexplained feature of most discs
Context: Warps occurring in galactic discs have been studied extensively in
HI and in the optical, but rarely in the near-infrared (NIR) bands that trace
the older stellar populations.
Aims: We provide NIR data of nearby edge-on galaxies, combined with optical
observations, for direct comparison of the properties of galactic warps as a
function of wavelength, and calculate warp curves for each galaxy and obtain
the characteristic warp parameters. We discuss these properties as possible
constraints to the different mechanisms that have been proposed for the
development and persistence of galactic warps.
Methods: We observed 20 galaxies that were selected from a statistically
complete diameter-limited subsample of edge-on disc galaxies. We used the Cerro
Tololo Infrared Imager (CIRIM) at the CTIO 1.5m Ritchey-Chretien telescope to
acquire the NIR data. We used the 1.54m Danish and 0.92m Dutch telescopes at
the European Southern Observatory's La Silla site for our optical observations.
Results: Our results show that 13 of our 20 sample galaxies are warped, with
the warp more pronounced in the optical than at NIR wavelengths. In the
remaining seven galaxies, no warp is apparent within the limitations of our
automated detection method. The transition between the unperturbed inner disc
and the outer, warped region is rather abrupt. S0 galaxies exhibit very small
or no warps. The magnetic model remains one of a number of interesting
formation scenarios.Comment: 16 page
Probing the Canis Major stellar over-density as due to the Galactic warp
Proper-motion, star counts and photometric catalog simulations are used to
explain the detected stellar over-density in the region of Canis Major (CMa),
claimed to be the core of a disrupted dwarf galaxy (Martin et al. 2004,
Bellazzini et al. 2003), as due to the Galactic warp and flare in the external
disk. We compare the kinematics of CMa M-giant selected sample with surrounding
Galactic disk stars in the UCAC2 catalog and find no peculiar proper motion
signature: CMa stars mimic thick disk kinematics. Moreover, when taking into
account the Galactic warp and flare of the disk, 2MASS star count profiles
reproduce the CMa stellar over-density. This star count analysis is confirmed
by direct comparison with synthetic color-magnitude diagrams simulated with the
Besancon models (Robin et al. 2003) that include the warp and flare of the
disk. The presented evidence casts doubt on the identification of the CMa
over-density as the core of a disrupted Milky Way satellite. This however does
not make clear the origin of over-densities responsible for the ring structure
in the anticenter direction of the Galactic halo (Newberg et al. 2002; Yanny et
al. 2003; Zaggia et al. 2004, in preparation).Comment: Accepted for publication in A&A Letters, 4 page
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