1,044 research outputs found
Anisotropic cosmological solutions to the gravity
We investigate anisotropic cosmological solutions of the theory with
non-minimal couplings between electromagnetic fields and gravity in
form. After we derive the field equations by the variational principle, we look
for spatially flat cosmological solutions with magnetic fields or electric
fields. Then we give exact anisotropic solutions by assuming the hyperbolic
expansion functions. We observe that the solutions approach to the isotropic
case in late-times.Comment: 16 pages, 5 figure
The influence of meteorological parameters on indoor and outdoor radon concentrations : a preliminary case study
In this study the influence of meteorology on indoor and outdoor radon concentrations in four different locations in a Mediterranean country have been studied. Indoor, daily radon concentrations were generally higher (0.2 – 85.0 Bq m-3) than outdoor daily concentrations (0.8 – 3.6 Bq m-3) in all locations studied with the exception of one that was built on pylons, thus reducing infiltration of radon from the ground. Indoor and outdoor meteorological parameters influence both the indoor and outdoor radon concentrations. In particular, outdoor wind speed and relative humidity show a negative correlation with both outdoor and indoor concentrations at all locations. Radon concentrations were also measured at two different levels of a terraced house (a common household type in Malta), in the basement and on ground floor. Results show that if the interconnecting door is left open, the radon in the basement infiltrates to the ground floor, increasing the average radon daily concentration in the living area by approximately 1.5 times.peer-reviewe
Asymmetric Ejecta of Cool Supergiants and Hypergiants in the Massive Cluster Westerlund 1
We report new 5.5 GHz radio observations of the massive star cluster Westerlund 1, taken by the Australia Telescope Compact Array, detecting nine of the ten yellow hypergiants (YHGs) and red supergiants (RSGs) within the cluster. Eight of nine sources are spatially resolved. The nebulae associated with the YHGs Wd1-4a, -12a and -265 demonstrate a cometary morphology - the first time this phenomenon has been observed for such stars. This structure is also echoed in the ejecta of the RSGs Wd1-20 and -26; in each case the cometary tails are directed away from the cluster core. The nebular emission around the RSG Wd1-237 is less collimated than these systems but once again appears more prominent in the hemisphere facing the cluster. Considered as a whole, the nebular morphologies provide compelling evidence for sculpting via a physical agent associated with Westerlund 1, such as a cluster wind
ALMA observations of the supergiant B[e] star Wd1-9
Mass-loss in massive stars plays a critical role in their evolution, although the precise mechanism(s) responsible – radiatively driven winds, impulsive ejection and/or binary interaction – remain uncertain. In this Letter, we present Atacama Large Millimetre/Submillimeter Array line and continuum observations of the supergiant B[e] star Wd1-9, a massive post-main-sequence object located within the starburst cluster Westerlund 1 (Wd1). We find it to be one of the brightest stellar point sources in the sky at millimetre wavelengths, with (serendipitously identified) emission in the H41α radio recombination line. We attribute these properties to a low velocity (∼100 km s-1 ) ionized wind, with an extreme mass-loss rate ≳6.4 × 105(d/5 kpc)1.5 Mȯyr-1. External to this is an extended aspherical ejection nebula indicative of a prior phase of significant mass-loss. Taken together, the millimetre properties of Wd1-9 show a remarkable similarity to those of the highly luminous stellar source MWC349A. We conclude that these objects are interacting binaries evolving away from the main sequence and undergoing rapid case-A mass transfer. As such they – and by extension the wider class of supergiant B[e] stars – may provide a unique window into the physics of a process that shapes the life-cycle of ∼70 per cent of massive stars found in binary systems
A CNL for Contract-Oriented Diagrams
We present a first step towards a framework for defining and manipulating
normative documents or contracts described as Contract-Oriented (C-O) Diagrams.
These diagrams provide a visual representation for such texts, giving the
possibility to express a signatory's obligations, permissions and prohibitions,
with or without timing constraints, as well as the penalties resulting from the
non-fulfilment of a contract. This work presents a CNL for verbalising C-O
Diagrams, a web-based tool allowing editing in this CNL, and another for
visualising and manipulating the diagrams interactively. We then show how these
proof-of-concept tools can be used by applying them to a small example
Thermodynamics of an attractive 2D Fermi gas
Thermodynamic properties of matter are conveniently expressed as functional
relations between variables known as equations of state. Here we experimentally
determine the compressibility, density and pressure equations of state for an
attractive 2D Fermi gas in the normal phase as a function of temperature and
interaction strength. In 2D, interacting gases exhibit qualitatively different
features to those found in 3D. This is evident in the normalized density
equation of state, which peaks at intermediate densities corresponding to the
crossover from classical to quantum behaviour.Comment: Contains minor revision
An ALMA 3mm continuum census of Westerlund 1
Context. Massive stars play an important role in both cluster and galactic evolution and the rate at which they lose mass is a key driver of both their own evolution and their interaction with the environment up to and including their terminal SNe explosions. Young massive clusters provide an ideal opportunity to study a co-eval population of massive stars, where both their individual properties and the interaction with their environment can be studied in detail.
Aims. We aim to study the constituent stars of the Galactic cluster Westerlund 1 in order to determine mass-loss rates for the diverse post-main sequence population of massive stars.
Methods. To accomplish this we made 3mm continuum observations with the Atacama Large Millimetre/submillimetre Array.
Results. We detected emission from 50 stars in Westerlund 1, comprising all 21 Wolf-Rayets within the field of view, plus eight cool and 21 OB super-/hypergiants. Emission nebulae were associated with a number of the cool hypergiants while, unexpectedly, a number of hot stars also appear spatially resolved.
Conclusions. We were able to measure the mass-loss rates for a unique population of massive post-main sequence stars at every stage of evolution, confirming a significant increase as stars transitioned from OB supergiant to WR states via LBV and/or cool hypergiant phases. Fortuitously, the range of spectral types exhibited by the OB supergiants provides a critical test of radiatively-driven wind theory and in particular the reality of the bi-stability jump. The extreme mass-loss rate inferred for the interacting binary Wd1-9 in comparison to other cluster members confirmed the key role binarity plays in massive stellar evolution. The presence of compact nebulae around a number of OB and WR stars is unexpected; by analogy to the cool super-/hypergiants we attribute this to confinement and sculpting of the stellar wind via interaction with the intra-cluster medium/wind. Given the morphology of core collapse SNe depend on the nature of the pre-explosion circumstellar environment, if this hypothesis is correct then the properties of the explosion depend not just on the progenitor, but also the environment in which it is located
The Need for Compliance Verification in Collaborative Business Processes
Compliance constrains processes to adhere to rules, standards, laws
and regulations. Non-compliance subjects enterprises to litigation and financial
fines. Collaborative business processes cross organizational and regional
borders implying that internal and cross regional regulations must be complied
with. To protect customs’ data, European enterprises must comply with the EU
data privacy regulation (general data protection regulation - GDPR) and each
member state’s data protection laws. An example of non-compliance with
GDPR is Facebook, it is accused for breaching subscriber trust. Compliance
verification is thus essential to deploy and implement collaborative business
process systems. It ensures that processes are checked for conformance to
compliance requirements throughout their life cycle. In this paper we take a
proactive approach aiming to discuss the need for design time preventative
compliance verification as opposed to after effect runtime detective approach.
We use a real-world case to show how compliance needs to be analyzed and
show the benefits of applying compliance check at the process design stag
Automation and validation of micronucleus detection in the 3D EpiDermâ„¢ human reconstructed skin assay and correl
Recent restrictions on the testing of cosmetic ingredients in animals have resulted in the need to test the genotoxic potential of chemicals exclusively in vitro prior to licensing. However, as current in vitro tests produce some misleading positive results, sole reliance on such tests could prevent some chemicals with safe or beneficial exposure levels from being marketed. The 3D human reconstructed skin micronucleus (RSMN) assay is a promising new in vitro approach designed to assess genotoxicity of dermally applied compounds. The assay utilises a highly differentiated in vitro model of the human epidermis. For the first time, we have applied automated micronucleus detection to this assay using MetaSystems Metafer Slide Scanning Platform (Metafer), demonstrating concordance with manual scoring. The RSMN assay's fixation protocol was found to be compatible with the Metafer, providing a considerably shorter alternative to the recommended Metafer protocol. Lowest observed genotoxic effect levels (LOGELs) were observed for mitomycin-C at 4.8 μg/ ml and methyl methanesulfonate (MMS) at 1750 μg/ml when applied topically to the skin surface. In-medium dosing with MMS produced a LOGEL of 20 μg/ml, which was very similar to the topical LOGEL when considering the total mass of MMS added. Comparisons between 3D medium and 2D LOGELs resulted in a 7-fold difference in total mass of MMS applied to each system, suggesting a protective function of the 3D microarchitecture. Interestingly, hydrogen peroxide (H2O 2), a positive clastogen in 2D systems, tested negative in this assay. A non-genotoxic carcinogen, methyl carbamate, produced negative results, as expected. We also demonstrated expression of the DNA repair protein N-methylpurine-DNA glycosylase in EpiDerm™. Our preliminary validation here demonstrates that the RSMN assay may be a valuable followup to the current in vitro test battery, and together with its automation, could contribute to minimising unnecessary in vivo tests by reducing in vitro misleading positives. © The Author 2014
The Need for Compliance Verification in Collaborative Business Processes
Compliance constrains processes to adhere to rules, standards, laws
and regulations. Non-compliance subjects enterprises to litigation and financial
fines. Collaborative business processes cross organizational and regional
borders implying that internal and cross regional regulations must be complied
with. To protect customs’ data, European enterprises must comply with the EU
data privacy regulation (general data protection regulation - GDPR) and each
member state’s data protection laws. An example of non-compliance with
GDPR is Facebook, it is accused for breaching subscriber trust. Compliance
verification is thus essential to deploy and implement collaborative business
process systems. It ensures that processes are checked for conformance to
compliance requirements throughout their life cycle. In this paper we take a
proactive approach aiming to discuss the need for design time preventative
compliance verification as opposed to after effect runtime detective approach.
We use a real-world case to show how compliance needs to be analyzed and
show the benefits of applying compliance check at the process design stag
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