1,105 research outputs found
Online tracking: Questioning the power of informed consent
Online tracking technologies have raised considerable concerns regarding privacy and the protection of personal data of users. In order to help users to regain control over their personal data, Europe has amended its ePrivacy directive towards an opt-in regime. There are however many open questions concerning its implementation, especially regarding the issue of informed consent. This paper explores how the new legal situation impacts on behavioral advertising practices via the storing and reading of cookies in the Netherlands. The results show that the majority of the surveyed parties involved in behavioural advertising do not inform users about the storing of cookies or the purposes of data processing of the subsequently obtained data, neither do they have obtained users' consent for the storage of cookies. We also found that the majority of users lack the skills and knowledge how to handle cookies. These findings critically question the wisdom of the informed consent regime which lies currently at the heart of Europe's ePrivacy directive. --Online behavioural advertising,profiling,cookies,informed consent,Do Not Track,ePrivacy Directive
What Determines the Depth of BALs? Keck HIRES Observations of BALQSO 1603+300
We find that the depth and shape of the broad absorption lines (BALs) in
BALQSO 1603+3002 are determined largely by the fraction of the emitting source
which is covered by the BAL flow. In addition, the observed depth of the BALs
is poorly correlated with their real optical depth. The implication of this
result is that abundance studies based on direct extraction of column densities
from the depth of the absorption troughs are unreliable. Our conclusion is
based on analysis of unblended absorption features of two lines from the same
ion (in this case the Si IV doublet), which allows unambiguous separation of
covering factor and optical depth effects. The complex morphology of the
covering factor as a function of velocity suggests that the BALs are produced
by several physically separated outflows. The covering factor is ion dependent
in both depth and velocity width. We also find evidence that in BALQSO
1603+3002 the flow does not cover the broad emission line region.Comment: 13 pages, 2 figures, accepted for publication in Ap
Type Ia Supernovae: An Examination of Potential Progenitors and the Redshift Distribution
We examine the possibility that supernovae type Ia (SN Ia) are produced by
white dwarfs accreting from Roche-lobe filling evolved companions, under the
assumption that a strong optically thick stellar wind from accretor is able to
stabilize the mass transfer. We show that if a mass transfer phase on a thermal
timescale precedes a nuclear burning driven phase, then such systems (of which
the supersoft X-ray sources are a subgroup) can account for about 10% of the
inferred SN Ia rate.
In addition, we examine the cosmic history of the supernova rate, and we show
that the ratio of the rate of SN Ia to the rate of supernovae produced by
massive stars (supernovae of types II, Ib, Ic) should increase from about z = 1
towards lower redshifts.Comment: 29 pages, Latex, 6 figures, aasms4.sty, psfig.sty, to appear in The
Astrophysical Journa
Soil water retention and hydraulic conductivity dynamics following tillage
Soil bulk density (ρb) may be purposely reduced in agricultural fields using tillage to improve hydraulic properties. However, tillage alters the soil structure, resulting in unstable soils. As the soil stabilizes, ρb increases over time. While this is known, studies on soil hydraulic properties in tilled soils, including comparisons between tilled and non-tilled soils, commonly assume a rigid soil structure. This study presents changes in soil water retention and saturated hydraulic conductivity (Ksat) as ρb increased dynamically with time following tillage at a loam-textured field site. Over the summer of 2015, soil cores were collected at several depths below the surface following precipitation events. Soil water retention curves and Ksat were determined using pressure cells and the constant head method, respectively. Tillage reduced ρb to 0.94 g cm−3. Changes in ρb increased with depth, reaching a ρb of 1.11 g cm−3 in the 0–5 cm layer, and a ρb of 1.42 g cm−3 at the deepest tilled layer. Soil water retention curves were markedly steeper for samples with higher ρb, indicating an overall increase in water retained at a soil matric potential (Ψ) of −33 kPa. Evaluation of two modeling approaches for water retention as a function ρbindicated that changes in water retention with increases in ρb could be reasonably estimated if a matching point was used. No clear relationship between Ksat and ρbwas obvious for ρb \u3c 1.06 cm3 cm−3, but for ρb \u3e 1.06 cm3 cm−3, Ksat decreased markedly (order of magnitude) as ρb increased. Hydraulic properties varied strongly depending on time since tillage and soil depth, and results have implications for models of tilled soils, as well as for studies comparing tilled and non-tilled soils
Trusted technology:Een onderzoek naar de toepassings-voorwaarden voor Privacy by Design in de elektronische dienstverlening van de overheid
Theoretical orbital period distributions of cataclysmic variables above the period gap: effects of circumbinary disks
The population of non magnetic cataclysmic variables evolving under the
influence of a circumbinary disk is investigated for systems above the upper
edge of the period gap at orbital periods greater than 2.75hr. For a fractional
mass input rate into the disk, corresponding to 3e-4 of the mass transfer rate,
the model systems exhibit a bounce at orbital periods greater than 2.75hr. The
simulations reveal that (1) some systems can exist as dwarf nova type systems
throughout their lifetime, (2) dwarf nova type systems can evolve into
nova-like systems as their mass transfer rate increases with increasing
circumbinary disk mass, and (3) nova-like systems can evolve back into dwarf
nova systems during their postbounce evolution to longer orbital periods. Among
these subclasses, nova-like cataclysmic variables would be the best candidates
to search for circumbinary disks at wavelengths greater than 10 micron. The
theoretical orbital period distribution of our population synthesis model is in
reasonable accord with the combined population of dwarf novae and nova-like
systems above the period gap, suggesting the possibility that systems with
unevolved donors need not detach and evolve below the period gap as in the
disrupted magnetic braking model. The resulting population furthermore reveals
the possible presence of systems with small mass ratios (a property of systems
exhibiting superhump phenomena at long orbital periods) and a preference of
O/Ne/Mg white dwarfs in dwarf nova systems in comparison to nova-like systems.
The importance of observational bias in accounting for the differing
populations is examined, and it is shown that an understanding of these effects
is necessary in order to confront the theoretical distributions with the
observed ones in a meaningful manner. (abridged)Comment: accepted for publication in Ap
A bite too big: dilemma's bij de implementatie van de Cookiewet in Nederland
Door een aanscherping van de Europese e-Privacyrichtlijn is bij het plaatsen van cookies, die bijvoorbeeld worden gebruikt om het surfgedrag van internetgebruikers te volgen, vooraf toestemming van de gebruiker nodig (en die dient gebaseerd te zijn op een geïnformeerde keuze). Deze aanscherping op Europees niveau (Nederland kent al een bepaling op grond waarvan cookies kunnen worden geweigerd) heeft geleid tot een brede discussie over de uitvoerbaarheid en de wijze van toezicht op de regelgeving omtrent cookies. Eind mei moet de richtlijn in nationale wetgeving zijn geïmplementeerd. Een wetsvoorstel daartoe ligt nu bij de Tweede Kamer. Ter voorbereiding heeft OPTA aan TNO en IViR gevraagd te onderzoeken wat de nieuwe juridische situatie in de praktijk betekent
Brown Dwarfs and the Cataclysmic Variable Period Minimum
Using improved, up-to-date stellar input physics tested against observations
of low-mass stars and brown dwarfs we calculate the secular evolution of
low-mass donor cataclysmic variables (CVs), including those which form with a
brown dwarf donor. Our models confirm the mismatch between the calculated
minimum period (Pmin ~ 70 min) and the observed short-period cut-off (~ 80 min)
in the CV period histogram. We find that tidal and rotational corrections
applied to the one-dimensional stellar structure equations have no significant
effect on the period minimum. Theoretical period distributions synthesized from
our model sequences always show an accumulation of systems at the minimum
period, a feature absent from the observed distribution. We suggest that
non-magnetic CVs become unobservable as they are effectively trapped in
permanent quiescence before they reach Pmin, and that small-number statistics
may hide the period spike for magnetic CVs.Comment: 10 pages; accepted for publication in MNRA
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