3,626 research outputs found
Zeeman-Tomography of the Solar Photosphere -- 3-Dimensional Surface Structures Retrieved from Hinode Observations
AIMS :The thermodynamic and magnetic field structure of the solar photosphere
is analyzed by means of a novel 3-dimensional spectropolarimetric inversion and
reconstruction technique. METHODS : On the basis of high-resolution,
mixed-polarity magnetoconvection simulations, we used an artificial neural
network (ANN) model to approximate the nonlinear inverse mapping between
synthesized Stokes spectra and the underlying stratification of atmospheric
parameters like temperature, line-of-sight (LOS) velocity and LOS magnetic
field. This approach not only allows us to incorporate more reliable physics
into the inversion process, it also enables the inversion on an absolute
geometrical height scale, which allows the subsequent combination of individual
line-of-sight stratifications to obtain a complete 3-dimensional reconstruction
(tomography) of the observed area. RESULTS : The magnetoconvection simulation
data, as well as the ANN inversion, have been properly processed to be
applicable to spectropolarimetric observations from the Hinode satellite. For
the first time, we show 3-dimensional tomographic reconstructions (temperature,
LOS velocity, and LOS magnetic field) of a quiet sun region observed by Hinode.
The reconstructed area covers a field of approximately 12000 by 12000 km and a
height range of 510 km in the photosphere. An enormous variety of small and
large scale structures can be identified in the 3-D reconstructions. The
low-flux region (B_{mag} = 20G) we analyzed exhibits a number of "tube-like"
magnetic structures with field strengths of several hundred Gauss. Most of
these structures rapidly loose their strength with height and only a few larger
structures can retain a higher field strength to the upper layers of the
photosphere.Comment: accepted for A&A Letter
A fast method for Stokes profile synthesis -- Radiative transfer modeling for ZDI and Stokes profile inversion
The major challenges for a fully polarized radiative transfer driven approach
to Zeeman-Doppler imaging are still the enormous computational requirements. In
every cycle of the iterative interplay between the forward process (spectral
synthesis) and the inverse process (derivative based optimization) the Stokes
profile synthesis requires several thousand evaluations of the polarized
radiative transfer equation for a given stellar surface model. To cope with
these computational demands and to allow for the incorporation of a full Stokes
profile synthesis into Doppler- and Zeeman-Doppler imaging applications as well
as into large scale solar Stokes profile inversions, we present a novel fast
and accurate synthesis method for calculating local Stokes profiles. Our
approach is based on artificial neural network models, which we use to
approximate the complex non-linear mapping between the most important
atmospheric parameters and the corresponding Stokes profiles. A number of
specialized artificial neural networks, are used to model the functional
relation between the model atmosphere, magnetic field strength, field
inclination, and field azimuth, on one hand and the individual components
(I,Q,U,V) of the Stokes profiles, on the other hand. We performed an extensive
statistical evaluation and show that our new approach yields accurate local as
well as disk-integrated Stokes profiles over a wide range of atmospheric
conditions. The mean rms errors for the Stokes I and V profiles are well below
0.2% compared to the exact numerical solution. Errors for Stokes Q and U are in
the range of 1%. Our approach does not only offer an accurate approximation to
the LTE polarized radiative transfer it, moreover, accelerates the synthesis by
a factor of more than 1000.Comment: A&A, in pres
Adjusting Bioactive Functions of Dairy Products via Processing
Milk is known for its high nutrient content that helps to maintain important body functions. In this regard, bioactive peptides that are encrypted in milk proteins and get released during processing and/or digestion might play a role. These peptides are able to inhibit enzymes, influence cell growth, or target specific receptors. The peptide profile that arises after protein digestion in the jejunum before the absorption into the blood takes place includes these bioactive peptides. The composition of the peptide profile is influenced strongly via processing and a modification in processing might target specific functionalities. Thermal, chemical, biochemical, and physical treatments affect protein digestion mainly by changing the protein structure for example via denaturation or protease actions. Parameters influencing this are external ones, like the matrix of the product, and internal ones, like specific enzyme deficiencies. However, considering all the important aspects that are involved, there might be the possibility in the future to adjust a bioactive function via processing
Understanding Marine Microbes, the Driving Engines of the Ocean
When you hear the word microbes, what comes to your mind? Something much too small to see and that makes you fall ill? Just because some microbes cause diseases that does not mean they are all evil. For example, in the marine (ocean) environment, the vast majority of microbes are good ones. They are the “driving engines” of the ocean and are essential for the health of our whole planet. Unfortunately, most of the marine microbes and their interactions with the marine environment are poorly understood. So, it is important to get an idea of which microbes are helping us and how they are doing this. These data will provide scientists with the knowledge to fight against big global challenges, such as climate change and environmental pollution. Unfortunately, it is very hard to study marine microbes due to their microscopic size, huge diversity, and their big home – the ocean. Therefore, we would like to engage “citizen scientists” in this project to help us to sample marine microbes so that we can identify them
Constraints on fluid flow processes in the Hellenic Accretionary Complex (eastern Mediterranean Sea) from numerical modeling
The dynamics of accretionary convergent margins are severely influenced by intense deformation and fluid expulsion. To quantify the fluid pressure and fluid flow velocities in the Hellenic subduction system, we set up 2-D hydrogeological numerical models following two seismic reflection lines across the Mediterranean Ridge. These profiles bracket the along-strike variation in wedge geometry: moderate compression and a >4 km thick underthrust sequence in the west versus enhanced compression and <1 km of downgoing sediment in the center. Input parameters were obtained from preexisting geophysical data, drill cores, and new geotechnical laboratory experiments. A permeability-porosity relationship was determined by a sensitivity analysis, indicating that porosity and intrinsic permeability are small. This hampers the expulsion of fluids and leads to the build up of fluid overpressure in the deeper portion of the wedge and in the underthrust sediment. The loci of maximum fluid pressure are mainly controlled by the compactional fluid source, which generally decreases toward the backstop. However, pore pressure is still high at the decollement level at distances <100 km from the deformation front, either by the incorporation of low permeability evaporites or additional compaction of the wedge sediments in the two profiles. In the west, however, formation of a wide accretionary complex is facilitated by high pore pressure zones. When compared to other large accretionary complexes such as Nankai or Barbados, our results not only show broad similarities but also that near-lithostatic pore pressures may be easier to maintain in the Hellenic Arc because of accentuated collision, some underthrust evaporates, and a thicker underthrust sequence
Semantically Guided Depth Upsampling
We present a novel method for accurate and efficient up- sampling of sparse
depth data, guided by high-resolution imagery. Our approach goes beyond the use
of intensity cues only and additionally exploits object boundary cues through
structured edge detection and semantic scene labeling for guidance. Both cues
are combined within a geodesic distance measure that allows for
boundary-preserving depth in- terpolation while utilizing local context. We
model the observed scene structure by locally planar elements and formulate the
upsampling task as a global energy minimization problem. Our method determines
glob- ally consistent solutions and preserves fine details and sharp depth
bound- aries. In our experiments on several public datasets at different levels
of application, we demonstrate superior performance of our approach over the
state-of-the-art, even for very sparse measurements.Comment: German Conference on Pattern Recognition 2016 (Oral
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