243 research outputs found
Polymorphic Structure of the Tumor Necrosis Factor (TNF) Locus: An NcoI Polymorphism in the First Intron of the Human TNF-ß Gene Correlates with A Variant Amino Acid in Position 26 and a Reduced Level of TNF-ß Production
The acclimative biogeochemical model of the southern North Sea
Ecosystem models often rely on heuristic descriptions of autotrophic growth that fail to reproduce various stationary and dynamic states of phytoplankton cellular composition observed in laboratory experiments. Here, we present the integration of an advanced phytoplankton growth model within a coupled three-dimensional physical-biogeochemical model and the application of the model system to the southern North Sea (SNS) defined on a relatively high resolution (∼1.5-4.5 km) curvilinear grid. The autotrophic growth model, recently introduced by Wirtz and Kerimoglu (2016), is based on a set of novel concepts for the allocation of internal resources and operation of cellular metabolism. The coupled model system consists of the General Estuarine Transport Model (GETM) as the hydrodynamical driver, a lower-trophic-level model and a simple sediment diagenesis model. We force the model system with realistic atmospheric and riverine fluxes, background turbidity caused by suspended particulate matter (SPM) and open ocean boundary conditions. For a simulation for the period 2000-2010, we show that the model system satisfactorily reproduces the physical and biogeochemical states of the system within the German Bight characterized by steep salinity; nutrient and chlorophyll (Chl) gradients, as inferred from comparisons against observation data from long-term monitoring stations; sparse in situ measurements; continuous transects; and satellites. The model also displays skill in capturing the formation of thin chlorophyll layers at the pycnocline, which is frequently observed within the stratified regions during summer. A sensitivity analysis reveals that the vertical distributions of phytoplankton concentrations estimated by the model can be qualitatively sensitive to the description of the light climate and dependence of sinking rates on the internal nutrient reserves. A non-acclimative (fixed-physiology) version of the model predicted entirely different vertical profiles, suggesting that accounting for physiological flexibility might be relevant for a consistent representation of the vertical distribution of phytoplankton biomass. Our results point to significant variability in the cellular chlorophyll-to-carbon ratio (Chl : C) across seasons and the coastal to offshore transition. Up to 3-fold-higher Chl : C at the coastal areas in comparison to those at the offshore areas contribute to the steepness of the chlorophyll gradient. The model also predicts much higher phytoplankton concentrations at the coastal areas in comparison to its non-acclimative equivalent. Hence, findings of this study provide evidence for the relevance of physiological flexibility, here reflected by spatial and seasonal variations in Chl : C, for a realistic description of biogeochemical fluxes, particularly in the environments displaying strong resource gradients. © 2017 Author(s)
Characteristic Dependence of Umbral Dots on their Magnetic Structure
Umbral dots (UDs) were observed in a stable sunspot in NOAA 10944 by the
Hinode Solar Optical Telescope on 2007 March 1. The observation program
consisted of blue continuum images and spectropolarimetric profiles of Fe I 630
nm line. An automatic detection algorithm for UDs was applied to the 2-hour
continuous blue continuum images, and using the obtained data, the lifetime,
size, and proper motion of UDs were calculated. The magnetic structure of the
sunspot was derived through the inversion of the spectropolarimetric profiles.
We calculated the correlations between UD's parameters (size, lifetime,
occurrence rate, proper motion) and magnetic fields (field strength,
inclination, azimuth), and obtained the following results: (1) Both the
lifetime and size of UDs are almost constant regardless of the magnetic field
strength at their emergence site. (2) The speed of UDs increases as the field
inclination angle at their emergence site gets larger. (3) The direction of
movement of UDs is nearly parallel to the direction of the horizontal component
of magnetic field in the region with strongly inclined field, while UDs in the
region with weakly inclined field show virtually no proper motion.
Our results describe the basic properties of magnetoconvection in sunspots.
We will discuss our results in comparison to recent MHD simulations by
Schussler & Vogler (2006) and Rempel et al. (2009).Comment: 22 pages, 10 figures, accepted for publication in Ap
Downflows in sunspot umbral dots
We study the velocity field of umbral dots at a resolution of 0.14". Our
analysis is based on full Stokes spectropolarimetric measurements of a pore
taken with the CRISP instrument at the Swedish 1-m Solar Telescope. We
determine the flow velocity at different heights in the photosphere from a
bisector analysis of the Fe I 630 nm lines. In addtion, we use the observed
Stokes Q, U, and V profiles to characterize the magnetic properties of these
structures. We find that most umbral dots are associated with strong upflows in
deep photospheric layers. Some of them also show concentrated patches of
downflows at their edges, with sizes of about 0.25", velocities of up to 1000
m/s, and enhanced net circular polarization signals. The downflows evolve
rapidly and have lifetimes of only a few minutes. These results appear to
validate numerical models of magnetoconvection in the presence of strong
magnetic fields.Comment: Final published version. For best quality figures, please download
the PS versio
Morphological properties of slender Ca II H fibrils observed by SUNRISE II
We use seeing-free high spatial resolution Ca II H data obtained by the
SUNRISE observatory to determine properties of slender fibrils in the lower
solar chromosphere. In this work we use intensity images taken with the SUFI
instrument in the Ca II H line during the second scientific flight of the
SUNRISE observatory to identify and track elongated bright structures. After
the identification, we analyze theses structures in order to extract their
morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with
an average width of around 180 km, a length between 500 km and 4000 km, an
average lifetime of ~400 s, and an average curvature of 0.002 arcsec^-1. The
maximum lifetime of the SCFs within our time series of 57 minutes is ~2000 s.
We discuss similarities and differences of the SCFs with other small-scale,
chromospheric structures such as spicules of type I and II, or Ca II K fibrils.Comment: Accepted for publication in The Astrophysical Journal Supplement
Serie
HLA class-I-transgenic mice as model system to study MHC-restricted antigen recognition in man
On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX
We study the photospheric evolution of an exploding granule observed in the
quiet Sun at high spatial () and temporal (31.5 s)
resolution by the imaging magnetograph Sunrise/IMaX in June 2009. These
observations show that the exploding granule is cospatial to a magnetic flux
emergence event occurring at mesogranular scale (up to 12 Mm area). Using
a modified version of the SIR code for inverting the IMaX spectropolarimetric
measurements, we obtain information about the magnetic configuration of this
photospheric feature. In particular, we find evidence of highly inclined
emerging fields in the structure, carrying a magnetic flux content up to Mx. The balance between gas and magnetic pressure in the region
of flux emergence, compared with a very quiet region of the Sun, indicates that
the additional pressure carried by the emerging flux increases by about 5% the
total pressure and appears to allow the granulation to be modified, as
predicted by numerical simulations. The overall characteristics suggest that a
multi-polar structure emerges into the photosphere, resembling an almost
horizontal flux sheet. This seems to be associated with exploding granules.
Finally, we discuss the origin of such flux emergence events.Comment: 19 pages, 12 figure + Appendix, accepted for ApJ. Figure 1 and Figure
5 are a low-quality version of the original one
The Sunrise Mission
The first science flight of the balloon-borne \Sunrise telescope took place
in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern
Canada. We describe the scientific aims and mission concept of the project and
give an overview and a description of the various hardware components: the 1-m
main telescope with its postfocus science instruments (the UV filter imager
SuFI and the imaging vector magnetograph IMaX) and support instruments (image
stabilizing and light distribution system ISLiD and correlating wavefront
sensor CWS), the optomechanical support structure and the instrument mounting
concept, the gondola structure and the power, pointing, and telemetry systems,
and the general electronics architecture. We also explain the optimization of
the structural and thermal design of the complete payload. The preparations for
the science flight are described, including AIV and ground calibration of the
instruments. The course of events during the science flight is outlined, up to
the recovery activities. Finally, the in-flight performance of the
instrumentation is briefly summarized.Comment: 35 pages, 17 figure
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