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Estimating the uncertainty of areal precipitation using data assimilation
We present a method to estimate spatially and temporally variable uncertainty of areal precipitation data. The aim of the method is to merge measurements from different sources, remote sensing and in situ, into a combined precipitation product and to provide an associated dynamic uncertainty estimate. This estimate should provide an accurate representation of uncertainty both in time and space, an adjustment to additional observations merged into the product through data assimilation, and flow dependency. Such a detailed uncertainty description is important for example to generate precipitation ensembles for probabilistic hydrological modelling or to specify accurate error covariances when using precipitation observations for data assimilation into numerical weather prediction models. The presented method uses the Local Ensemble Transform Kalman Filter and an ensemble nowcasting model. The model provides information about the precipitation displacement over time and is continuously updated by assimilation of observations. In this way, the precipitation product and its uncertainty estimate provided by the nowcasting ensemble evolve consistently in time and become flow-dependent. The method is evaluated in a proof of concept study focusing on weather radar data of four precipitation events. The study demonstrates that the dynamic areal uncertainty estimate outperforms a constant benchmark uncertainty value in all cases for one of the evaluated scores, and in half the number of cases for the other score. Thus, the flow dependency introduced by the coupling of data assimilation and nowcasting enables a more accurate spatial and temporal distribution of uncertainty. The mixed results achieved in the second score point out the importance of a good probabilistic nowcasting scheme for the performance of the method
Comment on ``The linear instability of magnetic Taylor-Couette flow with Hall effect''
In the paper we comment on (R\"udiger & Shalybkov, Phys. Rev. E. 69, 016303
(2004) (RS)), the instability of the Taylor--Couette flow interacting with a
homogeneous background field subject to Hall effect is studied. We correct a
falsely generalizing interpretation of results presented there which could be
taken to disprove the existence of the Hall--drift induced magnetic instability
described in Rheinhardt and Geppert, Phys. Rev. Lett. 88, 101103. It is shown
that in contrast to what is suggested by RS, no additional shear flow is
necessary to enable such an instability with a non--potential magnetic
background field, whereas for a curl--free one it is. In the latter case, the
instabilities found in RS in situations where neither a hydrodynamic nor a
magneto--rotational instability exists are demonstrated to be most likely
magnetic instead of magnetohydrodynamic. Further, some minor inaccuracies are
clarified.Comment: 3 pages, 1 figure; accepted by Physical Review
Temperature distribution in magnetized neutron star crusts. II. The effect of a strong toroidal component
We continue the study of the effects of a strong magnetic field on the
temperature distribution in the crust of a magnetized neutron star (NS) and its
impact on the observable surface temperature. Extending the approach initiated
in Geppert et al.(2004), we consider more complex and, hence, more realistic,
magnetic field structures but still restrict ourselves to axisymmetric
configurations. We put special emphasis on the heat blanketing effect of a
toroidal field component. We show that asymmetric temperature distributions can
occur and a crustal field consisting of dipolar poloidal and toroidal
components will cause one polar spot to be larger than the opposing one. These
two warm regions can be separated by an extended cold equatorial belt. We
present an internal magnetic field structure which can explain both the X-ray
and optical spectra of the isolated NS RXJ 1856-3754. We investigate the
effects of the resulting surface temperature profiles on the observable
lightcurve which an isolated thermally emitting NS would produce for different
field geometries. The lightcurves will be both qualitatively (deviations from
sinusoidal shape) and quantitatively (larger pulsed fraction for the same
observational geometry) different from those of a NS with an isothermal crust.
This opens the possibility to determine the interna} magnetic field strengths
and structures in NSs by modeling their X-ray lightcurves and spectra. The
striking similarities of our model calculations with the observed spectra and
pulse profiles of isolated thermally emitting NSs is an indication for the
existence of strong magnetic field components maintained by crustal currents.Comment: 9 pages, 10 figures in jpg-forma
The Occurrence of the Hall--Instability in Crusts of Isolated Neutron Stars
In former papers we showed that during the decay of a neutron star's magnetic
field under the influence of the Hall--drift, an unstable rise of small--scale
field structures at the expense of the large--scale background field may
happen. This linear stability analysis was based on the assumption of a uniform
density throughout the neutron star crust, whereas in reality the density and
all transport coefficients vary by many orders of magnitude. Here, we extend
the investigation of the Hall--drift induced instability by considering
realistic profiles of density and chemical composition, as well as background
fields with more justified radial profiles. Two neutron star models are
considered differing primarily in the assumption on the core matter equation of
state. For their cooling history and radial profiles of density and composition
we use known results to infer the conductivity profiles. These were fed into
linear calculations of a dipolar field decay starting from various initial
configurations. At different stages of the decay, snapshots of the magnetic
fields at the equator were taken to yield background field profiles for the
stability analysis. The main result is that the Hall instability may really
occur in neutron star crusts. Characteristic growth times are in the order of
\lesssim 10^4 ... 10^6 yrs depending on cooling age and background field
strength. The influence of the equation of state and of the initial field
configuration is discussed.Comment: 16 pages, 16 figures, PS, submitted to A&A. Justification/discussion
slightly changed/extended in replying to the referee. Changes on p. 3, 11,
13, framed by XXX mark
Politicization and political contests in and around contemporary multinational corporations: An introduction
© 2018, © The Author(s) 2018. This article looks at core arguments in international business, organization studies and surrounding academic fields that focus on the study of politicization and political contests in and around multinational corporations (MNCs). Two evident streams of debate are identified. Equally evident is that these streams hardly connect. One stream is mainly interested in studying politicization from the outside, whereas the other is mainly interested in politicization from within. As a way of connecting both streams, we introduce the circuits of power framework. Next, we introduce the contributions of our Special Issue, followed by concluding comments which distinguish five emergent themes. First, we show how the application of the circuits of power framework sheds new light on the study of political contests of MNCs. Second, we highlight that the role of nation states has not lost its significance as, for example, political corporate social responsibility (CSR) approaches would have us believe. Third, dominant ideologies play an important role in establishing and controlling circuits of power in and around MNCs. Fourth, it is vital to take labour issues into account in this field of study. Fifth, there is increasing evidence that asymmetric and hierarchical forms of organizing do not disappear in new MNC network forms
The proto--neutron--star dynamo -- viability and impediments
We study convective motions taken from hydrodynamic simulations of rotating
proto--neutron stars (PNSs) with respect to their ability to excite a dynamo
instability which may be responsible for the giant neutron star magnetic
fields. Since it is impossible to simulate the magnetic field evolution
employing the actual magnetic Reynolds numbers (\Rm) resulting from the
hydrodynamic simulations, (smallest) critical \Rms and the corresponding
field geometries are derived on the kinematic level by rescaling the velocity
amplitudes. It turns out that the actual values of \Rm are by many orders of
magnitude larger than the critical values found. A dynamo might therefore start
to act vigorously very soon after the onset of convection. But as in general
dynamo growth rates are non--monotonous functions of \Rm the later fate of
the magnetic field is uncertain. Hence, no reliable statements on the existence
and efficiency of PNS dynamos can be drawn without considering the interplay of
magnetic field and convection from the beginning. Likewise, in so far as
convection inside the PNS is regarded to be essential in re--launching the
supernova explosion, a revision of its role in this respect could turn out to
be necessary.Comment: 7 pages, 4 figures, accepted by Astronomy & Astrophysic
Toxicity of azo-dyes combined with TiO2 nanoparticles
Azo-dyes are organices compounds frequesntly used for food colring for example in sweets. A characteristic feature of az-=dyes is the axo-group (-N=N) as part of the chromophore. In parallel, nanoparticles (NPs) are more and more used as food additives and this, the encoubter of NPs with azo-dyes is highly likely. In particular, TiO2 NPs are inciroporated into foods under the tearm E171
Nanotechnology and azo-dyes in sweets
Nanotechnology is a fast growing field and consider as a key-technology of the 21st century. Nanoparticles are not only used in high-tech products or medical devices but are also more and more incorporated in food producers, for example in sweets. In addition, for food-coloring, azo-dyes are frequently used which makes an encounter of azo-dyes and nanoparticles unavoidable, The aim of this work was the isolation and characterisation of these dyes without including nanoparticles in a selected sweet product
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