871 research outputs found
Het onderzoek naar oorzaken en bestrijdingsmogelijkheden van aardappelschurft, verricht in de periode 1962 - 1972 in het kader van de activiteiten van de aardappelschurftcommissie
Flaring and self-shadowed disks around Herbig Ae stars: simulations for 10 micron interferometers
We present simulations of the interferometric visibilities of Herbig Ae star
disks. We investigate whether interferometric measurements in the 10 micrometer
atmospheric window are sensitive to the presence of an increased scale height
at the inner disk edge, predicted by recent models. Furthermore, we investigate
whether such measurements can discriminate between disks with a ``flaring''
geometry and disks with a ``flat'' geometry. We show that both these questions
can be addressed, using measurements at a small number of appropriately chosen
baselines. The classification of Herbig Ae stars in two groups, based on the
appearance of the spectral energy distribution (SED), has been attributed to a
difference in disk geometry. Sources with a group I SED would have a flaring
outer disk geometry, whereas the disk of group II sources is proposed to be
flat (or ``self-shadowed''). We show that this hypothesis can be tested using
long-baseline interferometric measurements in the micrometer atmospheric
window.Comment: 10 pages, 7 figures, accepted for publiction in Astronomy and
Astrophysic
Onderzoek naar de bodemfysische eigenschappen op het kavelinrichtingsproefveld Halsema in de ruilverkaveling "De Marne"
Onderzoek naar de stevigheid van de toplaag van de sportvelden in de gemeente Haren in de winter 1970/1971
petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
We present the easy-to-use, publicly available, Python package petitRADTRANS,
built for the spectral characterization of exoplanet atmospheres. The code is
fast, accurate, and versatile; it can calculate both transmission and emission
spectra within a few seconds at low resolution ( = 1000;
correlated-k method) and high resolution (;
line-by-line method), using only a few lines of input instruction. The somewhat
slower correlated-k method is used at low resolution because it is more
accurate than methods such as opacity sampling. Clouds can be included and
treated using wavelength-dependent power law opacities, or by using optical
constants of real condensates, specifying either the cloud particle size, or
the atmospheric mixing and particle settling strength. Opacities of amorphous
or crystalline, spherical or irregularly-shaped cloud particles are available.
The line opacity database spans temperatures between 80 and 3000 K, allowing to
model fluxes of objects such as terrestrial planets, super-Earths, Neptunes, or
hot Jupiters, if their atmospheres are hydrogen-dominated. Higher temperature
points and species will be added in the future, allowing to also model the
class of ultra hot-Jupiters, with equilibrium temperatures K. Radiative transfer results were tested by cross-verifying the low- and
high-resolution implementation of petitRADTRANS, and benchmarked with the
petitCODE, which itself is also benchmarked to the ATMO and Exo-REM codes. We
successfully carried out test retrievals of synthetic JWST emission and
transmission spectra (for the hot Jupiter TrES-4b, which has a of
1800 K). The code is publicly available at
http://gitlab.com/mauricemolli/petitRADTRANS, and its documentation can be
found at https://petitradtrans.readthedocs.io.Comment: 17 pages, 7 figures, published in A&
Onderzoek naar de oorzaken van de slechte bespeelbaarheid van enkele sportvelden in Den Haag
De dienst gemeente-plantsoenen van 's-Gravenhage heeft verzocht aandacht te besteden aan de slechte bespeelbaarheid van verscheidene van hun sportvelden (voetbal en hockey). Het probleem is , dat in natte perioden in herfst en winter te lang water op het veld blijft staan of de toplaag van het terrein te zacht wordt, waardoor het sportveld te vaak voor wedstrijden moet worden afgekeurd. Ook een te gladde toplaag wordt vaak, vooral bij hockey, als minder gewenst beschouwd. Het verzoek om enig onderzoek hield ook verband met het feit dat men de indruk had, dat het bodemkundige aspect bij aanleg en onderhoud van sportvelden nog een verwaarloosd terrein van onderzoek is
Scattered light images of spiral arms in marginally gravitationally unstable discs with an embedded planet
Scattered light images of transition discs in the near-infrared often show
non-axisymmetric structures in the form of wide-open spiral arms in addition to
their characteristic low-opacity inner gap region. We study self-gravitating
discs and investigate the influence of gravitational instability on the shape
and contrast of spiral arms induced by planet-disc interactions.
Two-dimensional non-isothermal hydrodynamical simulations including viscous
heating and a cooling prescription are combined with three-dimensional dust
continuum radiative transfer models for direct comparison to observations. We
find that the resulting contrast between the spirals and the surrounding disc
in scattered light is by far higher for pressure scale height variations, i.e.
thermal perturbations, than for pure surface density variations. Self-gravity
effects suppress any vortex modes and tend to reduce the opening angle of
planet-induced spirals, making them more tightly wound. If the disc is only
marginally gravitationally stable with a Toomre parameter around unity, an
embedded massive planet (planet-to-star mass ratio of ) can trigger
gravitational instability in the outer disc. The spirals created by this
instability and the density waves launched by the planet can overlap resulting
in large-scale, more open spiral arms in the outer disc. The contrast of these
spirals is well above the detection limit of current telescopes.Comment: Accepted for publication in MNRAS; 13 pages, 8 figure
Voortzetting van het onderzoek naar het optreden van Cox's ziekte in de Noordoostpolder in de periode 1966 - 1968
Invloed van organische stof op de bodemstructuur : verslag van ruim 25 jaar onderzoek op de 'Drie Miniatuur Organische-Stofbedrijven (IB 0006)' op het proefbedrijf 'Dr. Lovinkhoeve' te Marknesse
Report of more than 25 years of research on an experimental farm in the Netherland
Betekenis van groenbemesting voor de structuur van de grond
Green manuring can be quite effective only on soils that are very susceptible to slaking due to low calcium content and/or poor drainag
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