1,456 research outputs found
Stellar Oscillations Network Group
Stellar Oscillations Network Group (SONG) is an initiative aimed at designing
and building a network of 1m-class telescopes dedicated to asteroseismology and
planet hunting. SONG will have 8 identical telescope nodes each equipped with a
high-resolution spectrograph and an iodine cell for obtaining precision radial
velocities and a CCD camera for guiding and imaging purposes. The main
asteroseismology targets for the network are the brightest (V<6) stars. In
order to improve performance and reduce maintenance costs the instrumentation
will only have very few modes of operation. In this contribution we describe
the motivations for establishing a network, the basic outline of SONG and the
expected performance.Comment: Proc. Vienna Workshop on the Future of Asteroseismology, 20 - 22
September 2006. Comm. in Asteroseismology, Vol. 150, in the pres
ASTEC -- the Aarhus STellar Evolution Code
The Aarhus code is the result of a long development, starting in 1974, and
still ongoing. A novel feature is the integration of the computation of
adiabatic oscillations for specified models as part of the code. It offers
substantial flexibility in terms of microphysics and has been carefully tested
for the computation of solar models. However, considerable development is still
required in the treatment of nuclear reactions, diffusion and convective
mixing.Comment: Astrophys. Space Sci, in the pres
The Effect of Crystallization on the Pulsations of White Dwarf Stars
We consider the pulsational properties of white dwarf star models with
temperatures appropriate for the ZZ Ceti instability strip and with masses
large enough that they should be substantially crystallized. Our work is
motivated by the existence of a potentially crystallized DAV, BPM 37093, and
the expectation that digital surveys in progress will yield many more such
massive pulsators.
A crystallized core makes possible a new class of oscillations, the torsional
modes, although we expect these modes to couple at most weakly to any motions
in the fluid and therefore to remain unobservable. The p-modes should be
affected at the level of a few percent in period, but are unlikely to be
present with observable amplitudes in crystallizing white dwarfs any more than
they are in the other ZZ Ceti's. Most relevant to the observed light variations
in white dwarfs are the g-modes. We find that the kinetic energy of these modes
is effectively excluded from the crystallized cores of our models. As
increasing crystallization pushes these modes farther out from the center, the
mean period spacing between radial overtones increases substantially with the
crystallized mass fraction. In addition, the degree and structure of mode
trapping is affected. The fact that some periods are strongly affected by
changes in the crystallized mass fraction while others are not suggests that we
may be able to disentangle the effects of crystallization from those due to
different surface layer masses.Comment: 18 pages, 5 figures, accepted on 1999 July 2 for publication in the
Astrophysical Journa
Invest to Save: Report and Recommendations of the NSF-DELOS Working Group on Digital Archiving and Preservation
Digital archiving and preservation are important areas for research and development, but there is no agreed upon set of priorities or coherent plan for research in this area. Research projects in this area tend to be small and driven by particular institutional problems or concerns. As a consequence, proposed solutions from experimental projects and prototypes tend not to scale to millions of digital objects, nor do the results from disparate projects readily build on each other. It is also unclear whether it is worthwhile to seek general solutions or whether different strategies are needed for different types of digital objects and collections. The lack of coordination in both research and development means that there are some areas where researchers are reinventing the wheel while other areas are neglected.
Digital archiving and preservation is an area that will benefit from an exercise in analysis, priority setting, and planning for future research. The WG aims to survey current research activities, identify gaps, and develop a white paper proposing future research directions in the area of digital preservation. Some of the potential areas for research include repository architectures and inter-operability among digital archives; automated tools for capture, ingest, and normalization of digital objects; and harmonization of preservation formats and metadata. There can also be opportunities for development of commercial products in the areas of mass storage systems, repositories and repository management systems, and data management software and tools.
Deeply penetrating banded zonal flows in the solar convection zone
Helioseismic observations have detected small temporal variations of the
rotation rate below the solar surface corresponding to the so-called `torsional
oscillations' known from Doppler measurements of the surface. These appear as
bands of slower and faster than average rotation moving equatorward. Here we
establish, using complementary helioseismic observations over four years from
the GONG network and from the MDI instrument on board SOHO, that the banded
flows are not merely a near-surface phenomenon: rather they extend downward at
least 60 Mm (some 8% of the total solar radius) and thus are evident over a
significant fraction of the nearly 200 Mm depth of the solar convection zone.Comment: 4 pages, 4 figures To be published in ApJ Letters (accepted 3/3/2000
Regular modes in rotating stars
Despite more and more observational data, stellar acoustic oscillation modes
are not well understood as soon as rotation cannot be treated perturbatively.
In a way similar to semiclassical theory in quantum physics, we use acoustic
ray dynamics to build an asymptotic theory for the subset of regular modes
which are the easiest to observe and identify. Comparisons with 2D numerical
simulations of oscillations in polytropic stars show that both the frequency
and amplitude distributions of these modes can accurately be described by an
asymptotic theory for almost all rotation rates. The spectra are mainly
characterized by two quantum numbers; their extraction from observed spectra
should enable one to obtain information about stellar interiors.Comment: 5 pages, 4 figures, discussion adde
Behavioural side effects of inhaled corticosteroids among children and adolescents with asthma
BACKGROUND: Inhalation corticosteroids (ICS) are prescribed for treatment of asthma in approximately 3% of all children in Denmark. Despite limited evidence, case reports suggest that ICS-related behavioural adverse drug events (ADEs) may be frequent. In general, underreporting of ADEs to official databases is common, and little is known about doctorâs clinical experiences with behavioural ADEs when prescribing ICS for children with asthma. The objective was to investigate the extent of behavioural ADEs in children with asthma treated with ICS by comparing database findings to experiences of specialist doctors. METHODS: First, databases of the European Medicines Agency (EMA) and the Danish Medicines Agency (DKMA) were searched for reports made by healthcare professionals about behavioural ADEs in children from 2009 to 2018. Second, questionnaire data on behavioural ADEs were collected from eight of the 11 specialist doctors responsible for treating children with asthma at the six paediatric departments in Central Denmark Region and North Denmark Region. RESULTS: EMA and DKMA had registered 104 and 3 reports, respectively, on behavioural ADEs during the 10-year study period. In contrast, five of the eight specialist doctors (45.5%) had experienced patients who had developed behavioural changes during ICS treatment. However, none of the five specialist doctors had filed reports on these events to DKMA. CONCLUSION: Behaviour-related ADEs to ICS in children with asthma are likely to be highly underreported in official databases and doctors treating children with ICS should be aware of potential ADEs and consider submitting ADE reports whenever appropriate. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12931-022-02112-8
A quantitative assessment method for Ascaris eggs on hands.
The importance of hands in the transmission of soil transmitted helminths, especially Ascaris and Trichuris infections, is under-researched. This is partly because of the absence of a reliable method to quantify the number of eggs on hands. Therefore, the aim of this study was to develop a method to assess the number of Ascaris eggs on hands and determine the egg recovery rate of the method. Under laboratory conditions, hands were seeded with a known number of Ascaris eggs, air dried and washed in a plastic bag retaining the washing water, in order to determine recovery rates of eggs for four different detergents (cationic [benzethonium chloride 0.1% and cetylpyridinium chloride CPC 0.1%], anionic [7X 1% - quadrafos, glycol ether, and dioctyl sulfoccinate sodium salt] and non-ionic [Tween80 0.1% -polyethylene glycol sorbitan monooleate]) and two egg detection methods (McMaster technique and FLOTAC). A modified concentration McMaster technique showed the highest egg recovery rate from bags. Two of the four diluted detergents (benzethonium chloride 0.1% and 7X 1%) also showed a higher egg recovery rate and were then compared with de-ionized water for recovery of helminth eggs from hands. The highest recovery rate (95.6%) was achieved with a hand rinse performed with 7X 1%. Washing hands with de-ionized water resulted in an egg recovery rate of 82.7%. This washing method performed with a low concentration of detergent offers potential for quantitative investigation of contamination of hands with Ascaris eggs and of their role in human infection. Follow-up studies are needed that validate the hand washing method under field conditions, e.g. including people of different age, lower levels of contamination and various levels of hand cleanliness
Seismic detection of acoustic sharp features in the CoRoT target HD49933
The technique of determining the acoustic location of layers of sharp changes
in the sound speed inside a star from the oscillatory signal in its frequencies
is applied on a solar-type star, the CoRoT target, HD49933. We are able to
determine the acoustic depth of the second helium ionisation zone of HD49933 to
be 794 +55/-68 seconds. The acoustic depth of the base of the convective zone
is found to be 1855 +173/-412 seconds where the large error bars reflect the
ambiguity in the result, which is difficult to determine with present precision
on the frequencies because of the intrinsically weak nature of the signal. The
positions of both these layers are consistent with those in a representative
stellar model of HD49933.Comment: Accepted for publication in Astronomy & Astrophysic
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