1,251 research outputs found
Global Scale Atmospheric Processes Research Program Review
Global modeling; satellite data assimilation and initialization; simulation of future observing systems; model and observed energetics; dynamics of planetary waves; First Global Atmospheric Research Program Global Experiment (FGGE) diagnosis studies; and National Research Council Research Associateship Program are discussed
Large-Scale Agile Transformation: A Case Study of Transforming Business, Development and Operations
Today, product development organizations are adopting agile methods in units outside the software development unit, such as in sales, market, legal, operations working with the customer. This broader adoption of agile methods has been labeled large-scale agile transformation and is considered a particular type of organizational change, originating in the software development units. So far, there is little research-based advice on conducting such transformations. Aiming to contribute towards providing relevant research advice on large-scale agile transformation, we apply a research-based framework for evaluating organizational agility on a product development program in a maritime service provider organization. We found that doing a large-scale agile transformation involves many significant challenges, such as having a shared understanding of the problem, getting access to users, and getting commitment to change that needs to be done. In order to overcome such challenges, we discuss the need for a holistic and integrated approach to agile transformation involving all the units linked to software development.publishedVersio
Comparative Modelling of the Spectra of Cool Giants
Our ability to extract information from the spectra of stars depends on
reliable models of stellar atmospheres and appropriate techniques for spectral
synthesis. Various model codes and strategies for the analysis of stellar
spectra are available today. We aim to compare the results of deriving stellar
parameters using different atmosphere models and different analysis strategies.
The focus is set on high-resolution spectroscopy of cool giant stars. Spectra
representing four cool giant stars were made available to various groups and
individuals working in the area of spectral synthesis, asking them to derive
stellar parameters from the data provided. The results were discussed at a
workshop in Vienna in 2010. Most of the major codes currently used in the
astronomical community for analyses of stellar spectra were included in this
experiment. We present the results from the different groups, as well as an
additional experiment comparing the synthetic spectra produced by various codes
for a given set of stellar parameters. Similarities and differences of the
results are discussed. Several valid approaches to analyze a given spectrum of
a star result in quite a wide range of solutions. The main causes for the
differences in parameters derived by different groups seem to lie in the
physical input data and in the details of the analysis method. This clearly
shows how far from a definitive abundance analysis we still are.Comment: accepted for publication in A&A. This version includes also the
online tables. Reference spectra will later be available via the CD
Imprints of Nuclear Symmetry Energy on Properties of Neutron Stars
Significant progress has been made in recent years in constraining the
density dependence of nuclear symmetry energy using terrestrial nuclear
laboratory data. Around and below the nuclear matter saturation density, the
experimental constraints start to merge in a relatively narrow region. At
supra-saturation densities, there are, however, still large uncertainties.
After summarizing the latest experimental constraints on the density dependence
of nuclear symmetry energy, we highlight a few recent studies examining
imprints of nuclear symmetry energy on the binding energy, energy release
during hadron-quark phase transitions as well as the -mode frequency and
damping time of gravitational wave emission of neutron stars.Comment: 10 pages. Invited talk given in the Nuclear Astrophysics session of
INPC2010, July 4-9, 2010, Vancouver, Canada; Journal of Physics: Conference
Series (2011
A brown dwarf desert for intermediate mass stars in Sco OB2?
We present JHK observations of 22 intermediate-mass stars in Sco OB2,
obtained with VLT/NACO. The survey was performed to determine the status of
(sub)stellar candidate companions of A and late-B members. The distinction
between companions and background stars is by a comparison with isochrones and
statistical arguments. We are sensitive to companions in the separation range
0.1''-11'' (13-1430 AU) and K<17. We detect 62 secondaries of which 18 are
physical companions (3 new), 11 candidates, and 33 background stars. The
companion masses are in the range 0.03<M<1.19 Msun, with mass ratios
0.06<q<0.55. We include in our sample a subset of 9 targets with multi-color
ADONIS observations from Kouwenhoven et al. (2005). In the ADONIS survey
secondaries with K12 as
background stars. Our multi-color analysis demonstrates that the simple K=12
criterion correctly classifies the secondaries in ~80% of the cases. We
reanalyse the total ADONIS/NACO sample and conclude that of the 176
secondaries, 25 are physical companions, 55 are candidates, and 96 are
background stars. Although we are sensitive and complete to brown dwarfs as
faint as K=14 in the separation range 130-520 AU, we detect only one, giving a
brown dwarf companion fraction of 0.5% (M>30 MJ). However, the number of brown
dwarfs is consistent with an extrapolation of the stellar companion mass
distribution. This indicates that the physical mechanism for the formation of
brown dwarfs around intermediate mass stars is similar to that of stellar
companions, and that the embryo ejection mechanism does not need to be invoked
in order to explain the small number of brown dwarf companions among these
stars.Comment: 29 pages, 9 figures, accepted by A&
The AMBRE project: A new synthetic grid of high-resolution FGKM stellar spectra
Large grids of synthetic spectra covering a widespread range of stellar
parameters are mandatory for different stellar and (extra-)Galactic physics
applications. Such large grids can be used for the automatic parametrisation of
stellar spectra such as that performed within the AMBRE project for which the
main goal is the stellar atmospheric parameters determination for the few
hundreds of thousands of archived spectra of four ESO spectrographs. To fulfil
the needs of AMBRE and future similar projects, we have computed a grid of
synthetic spectra over the whole optical domain for cool to very cool stars of
any luminosity with metallicities varying from 10-5 to 10 times the solar
metallicity, and considering large variations in the chemical content of the
{\alpha}-elements. New generation MARCS model atmospheres and the Turbospectrum
code for radiative transfer have been used. We have also taken into account as
complete as possible atomic and molecular linelists. A new grid of 16783 high
resolution spectra over the wavelength range 3000 to 12000 {\AA} has been
computed with a spectral resolution always larger than 150000. Normalised and
absolute flux versions are available over a wide range of stellar atmospheric
parameters for stars of FGKM spectral types. The covered parameters are
2500K\leqTeff\leq8000K, -0.5\leqlog(g)\leq5.5dex, -5.0\leq[M/H]\leq+1.0 dex and
five different values of the enrichment in {\alpha}-elements have been
considered (0.0, \pm0.2 dex and \pm0.4 dex around the standard values). This
grid is made publicly available through the POLLUX database (about 50% of the
spectra are already included in this database) and in FITS format upon request
to the authors.Comment: Accepted by A&
GTP and Ca2+ Modulate the Inositol 1,4,5-Trisphosphate-Dependent Ca2+ Release in Streptolysin O-Permeabilized Bovine Adrenal Chromaffin Cells
The inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release was studied using streptolysin O-permeabilized bovine adrenal chromaffin cells. The IP3-induced Ca2+ release was followed by Ca2+ reuptake into intracellular compartments. The IP3-induced Ca2+ release diminished after sequential applications of the same amount of IP3. Addition of 20 μM GTP fully restored the sensitivity to IP3. Guanosine 5'-O-(3-thio)triphosphate (GTPγS) could not replace GTP but prevented the action of GTP. The effects of GTP and GTPγS were reversible. Neither GTP nor GTPγS induced release of Ca2+ in the absence of IP3. The amount of Ca2+ whose release was induced by IP3 depended on the free Ca2+ concentration of the medium. At 0.3 μM free Ca2+, a half-maximal Ca2+ release was elicited with ∼0.1 μM IP3. At 1 μM free Ca2+, no Ca2+ release was observed with 0.1 μM IP3; at this Ca2+ concentration, higher concentrations of IP3 (0.25 μM) were required to evoke Ca2+ release. At 8 μM free Ca2+, even 0.25 μM IP3 failed to induce release of Ca2+ from the store. The IP3-induced Ca2+ release at constant low (0.2 μM) free Ca2+ concentrations correlated directly with the amount of stored Ca2+. Depending on the filling state of the intracellular compartment, 1 mol of IP3 induced release of between 5 and 30 mol of Ca2+
Requirements modelling and formal analysis using graph operations
The increasing complexity of enterprise systems requires a more advanced
analysis of the representation of services expected than is currently possible.
Consequently, the specification stage, which could be facilitated by formal
verification, becomes very important to the system life-cycle. This paper presents
a formal modelling approach, which may be used in order to better represent
the reality of the system and to verify the awaited or existing system’s properties,
taking into account the environmental characteristics. For that, we firstly propose
a formalization process based upon properties specification, and secondly we
use Conceptual Graphs operations to develop reasoning mechanisms of verifying
requirements statements. The graphic visualization of these reasoning enables us
to correctly capture the system specifications by making it easier to determine if
desired properties hold. It is applied to the field of Enterprise modelling
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