77 research outputs found
Dichroic Dipole Antenna Membranes from Aligned Linear BOPHY Dyes
No full text<p>data of the open access publication https://doi.org/10.1002/admi.202101490</p>
EXISTENCE AND UNIQUENESS OF THE INTEGRATED DENSITY OF STATES FOR SCHRÖDINGER OPERATORS WITH MAGNETIC FIELDS AND UNBOUNDED RANDOM POTENTIALS
No full text The object of the present study is the integrated density of states of a quantum particle in multi-dimensional Euclidean space which is characterized by a Schrödinger operator with a constant magnetic field and a random potential which may be unbounded from above and from below. For an ergodic random potential satisfying a simple moment condition, we give a detailed proof that the infinite-volume limits of spatial eigenvalue concentrations of finite-volume operators with different boundary conditions exist almost surely. Since all these limits are shown to coincide with the expectation of the trace of the spatially localized spectral family of the infinite-volume operator, the integrated density of states is almost surely non-random and independent of the chosen boundary condition. Our proof of the independence of the boundary condition builds on and generalizes certain results obtained by S. Doi, A. Iwatsuka and T. Mine (Math. Z. 237 (2001) 335) and S. Nakamura (J. Funct. Anal. 173 (2001) 136). </jats:p
Results of lake water analysis from Lake Arendsee in Saxony-Anhalt during the Inland Water Remote Sensing Validation Campaign 2017
No full textLake Arendsee originated from salt depressions (sinkhole) 822 A.D. and in 1685 (Scharf 1998). Due to the maximum depth of 49 m (mean depth 29 m) and a surface area of about 5 km², Lake Arendsee has a volume of approx. 150 Mio. m³. According to Scharf (1998), eutrophication dates back to 1970 when sewage loading of the town of Arendsee and drainage of Lake Fauler See into Lake Arendsee raised nutrient loading. Due to the long residence time of 114 years, no recovery of the lake occurred up to now although several restoration measures were applied (e.g. Stüben et al. 1998; Hupfer and Lewandowski 2005). Lake Arendsee regularly expresses, large, surface scum forming blooms of cyanobacteria.
This publication series includes datasets collected on Lake Arendsee during the Inland Water Remote Sensing Validation Campaign 2017 (Bumberger et al. 2023)
Rapid Eutrophication of a Clearwater Lake: Trends and Potential Causes Inferred From Phosphorus Mass Balance Analyses
No full textMany clearwater lakes increasingly show symptoms of eutrophication, but the underlying causes are largely unknown. We combined long-term water chemistry data, multi-year sediment trap measurements, sediment analyses and simple mass balance models to elucidate potential causes of eutrophication of a deep temperate clearwater lake, where total phosphorus (TP) concentrations quadrupled within a decade, accompanied by expanding hypolimnetic anoxia. Discrepancies between modeled and empirically determined P inputs suggest that the observed sharp rise in TP was driven by internal processes. The magnitude of seasonal variation in TP greatly increased at the same time, both in surface and deep water, partly decoupled from deep water oxygen conditions. A positive correlation between annual P loss from the upper water column and hypolimnetic P accumulation could hint at a short-circuited P cycle involving lateral TP transport from shallow-water zones and deposition and release from sediments in deep water. This hypothesis is also supported by P budgets for the upper 20 m during stable summer stratification, suggesting that sediments in shallow lake areas acted as a P net source until 2018. These changes are potentially related to shifts in submerged macrophytes from wintergreen charophyte meadows (Nitellopsis obtusa) to annual free-floating hornwort (Ceratophyllum demersum) and to increased sulfide formation, promoting iron fixation in the sediments. Iron bound to sulfur is unavailable for binding P, resulting in a positive feedback between P release in shallow lake areas, primary productivity, macrophyte community structure and redox-dependent sediment biogeochemistry. Overall, our results suggest that relationships more complex than the commonly invoked increase in internal P release under increasingly anoxic conditions can drive rapid lake eutrophication. Since the proportion of littoral areas is typically large even in deep stratified lakes, littoral processes may contribute more frequently to the rapid lake eutrophication trends observed around the world than is currently recognized.Full Tex
Die IL-4-abhängige Inhibition der Expression des Mustererkennungsrezeptors Mincle
No full textHintergrund und Ziele
Die C-Typ-Lektin-Rezeptoren des Dectin-2-Clusters Mincle, MCL und Dectin-2 erkennen immunologisch Bestandteile der Zellwand von Mycobacterium tuberculosis, beispielsweise den mykobakteriellen Cordfaktor durch MCL und Mincle. Nach Erkennung des Liganden Cordfactor werden antibakterielle Effektorfunktionen des angeborenen Immunsystems aktiviert und die Expression der Rezeptoren erhöht. Es wurde beobachtet, dass das Zytokin Interleukin-4, welches mit einer alternativen Makrophagenaktivierung assoziiert ist, die Expression dieser Rezeptoren inhibiert. In der vorliegenden Arbeit soll dieser Effekt charakterisiert werden.
Methoden
Es erfolgte die Analyse humaner und muriner antigenpräsentierender Zellen (Monozyten, Makrophagen, dendritische Zellen) in Zellkultur. Untersuchungen erfolgten nach Stimulation mit Liganden für C-Typ-Lektin-Rezeptoren (Trehalosedibehenat, Trehalosedimykolat), Toll-Like-Rezeptor 4 (Lipopolysaccharid) und weiterer Zytokine
(M-CSF, GM-CSF) in An- oder Abwesenheit von Interleukin-4. Der Einfluss auf die Expression verschiedener C-Typ-Lektine wurde mittels RT-PCR und Durchflusszytometrie untersucht. Die Analyse der funktionellen Zytokinantwort erfolgte mittels ELISA.
Ergebnisse und Beobachtungen
Interleukin-4 induzierte eine konzentrationsabhängige, anhaltende Inhibition der Expression von Mincle und anderen C-Typ-Lektinen des Dectin-2-Clusters sowohl auf humanen als auch murinen Zellen, wobei der Effekt sowohl auf Makrophagen als auch auf dendritischen Zellen nachzuweisen war. Unter Interleukin-4 zeigte sich eine Inhibition der induzierten mRNA-Expression von Mincle nach Stimulation mit dessen Liganden, nicht jedoch nach Stimulation mit dem Toll-Like-Rezeptor-Agonisten Lipopolysaccharid. Die Inhibition der mRNA-Expression übersetzte sich in eine reduzierte Proteinexpression und eine reduzierte funktionelle Antwort auf Mincle-abhängige Stimuli im Sinne einer reduzierten Produktion proinflammatorischer Zytokine. Der Effekt war abhängig von dem im Interleukin-4 Signalweg wichtigen Transkriptionsfaktor STAT6.
Schlussfolgerungen
Interleukin-4 inhibiert die Expression der für die Erkennung von Mycobacterium tuberculosis wichtigen Mustererkennungsrezeptoren des Dectin-2-Clusters auf antigenpräsentierenden Zellen des angeborenen Immunsystems. Dieser Mechanismus könnte zu einer erhöhten Suszeptibilität und erhöhtem Reaktivierungsrisiko einer latenten Tuberkulose in einem von Th2-Zytokinen wie Interleukin-4 geprägten Milieu beitragen
Herstellung von LATP für den Einsatz als Festkörperelektrolyt und dessen Eigenschaften
No full textIn dieser Arbeit wird das oxidische Material Li₁₊ₓAlₓTi₂₋ₓ(PO₄)₃ (LATP) im Detail auf seine Eignung als Festkörperelektrolyt untersucht. Ausgehend von der Rohmaterialherstellung von LATP mittels Sol-Gel-Methoden über die Pulveraufbereitung bis zur Sinterung vollkeramischer Proben wird der vollständige Herstellungsprozess von LATP abgebildet und analysiert
A tribute to Peter Hupfer's 90th birthday
No full textThe development of science in the former German Democratic Republic (GDR) experienced some disruptions with the reunification of Germany. Nevertheless, it was possible to maintain a certain continuity in climate research, which can be seen as a personal merit of Prof. Dr. Peter Hupfer. The development of climate research from the 1950s to the present and his part in it will be acknowledged in the present article
Beiträge zur Klima- und Meeresforschung : Aus Anlass des 70. Geburtstages von Peter Hupfer
No full textThe occurrence, identification and environmental relevance of vivianite in waterlogged soils and aquatic sediments
No full textAbstractIn this article, we review the nature, occurrence and environmental relevance of the authigenic ferrous iron phosphate mineral vivianite (Fe3(PO4)2·8H2O) in waterlogged soils and aquatic sediments. We critically discuss existing work from freshwater and marine systems, laboratory studies and microbial batch culture experiments aiming to deduce common characteristics of the mineral's occurrence, and the processes governing its formation. Vivianite regularly occurs in close association with organic remains in iron-rich sediments. Simultaneously, it is a biogenic mineral product of metal reducing bacteria. These findings suggest that vivianite nucleation in natural systems is directed by the activity of such bacteria and crystal growth is particularly favoured within protected microzones. Taking into account recent findings from coastal marine sediments where vivianite authigenesis has been shown to be coupled to the anaerobic oxidation of methane, small-scale microbially mediated reactions appear to be crucial for the formation of vivianite. Small-scale heterogeneity within the sediment matrix may also explain why saturation calculations based upon bulk pore water constitutions often fail to accurately predict the occurrence of the mineral. Vivianite is not restricted to a specific trophic state of a system. The mineral forms in oligotrophic- as well as in eutrophic waters. However, depending on the iron inventory, the production, supply and degradation of organic matter determine the relative contribution of iron sulphide formation to the iron pool, and the concentration of inorganic phosphate and Fe2+ in pore waters. Thus, vivianite authigenesis is also governed by bulk chemical conditions such as the rate of sulphide formation relative to that of Fe2+ production. This situation allows stimulation of vivianite formation by iron supplementation aimed at restoring eutrophic lakes. Recent results from coastal marine sediments suggest that vivianite authigenesis is of significance for P burial in the marine realm. Vivianite authigenesis is likely important at the global scale, but has so far largely been ignored
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