Interannual and decadal variability of sea ice drift, concentration and thickness in the Weddell Sea

Sea ice concentrations in the Weddell Sea are subject to regional climate variability. The magnitude and origin of local trends in the sea ice coverage were studied using the bootstrap algorithm sea ice concentration data from the NSIDC for 1979-2006. The impact of atmospheric forcing such as air temperature, wind speed, sea level pressure and cloud coverage, gained from NCEP/NCAR reanalysis, was assessed by analyzing correlation coefficients between the respective atmospheric component and the sea ice concentrations. In addition, the variability of sea ice drift was analyzed using the Polar Pathfinder sea ice motion vectors, and the correlation with sea ice concentration was tested after an assessment of the product s uncertainties. The connection to the variability of sea ice thicknesses was derived by model simulations from the Finite Element Sea ice-Ocean Model (FESOM). It was found that sea ice concentrations increased in the eastern and decreased in the western Weddell Sea, predominantly in the marginal sea ice zone. There, and in coastal regions, temperatures are strongly negatively correlated to sea ice concentrations, whereas in the central Weddell Sea, mostly a positive correlation was assessed, especially during winter. From analyses of the wind field it was found that the prevailing westerlies at the Antarctic Peninsula frequently show a shift towards the south. The enhanced southward winds are expected to bring warmer air into the western and central Weddell Sea and are further expected to redistribute the sea ice from the west into the central and eastern regions. This would increase the sea ice concentrations in the central Weddell Sea due to enhanced compactness, although temperatures are increasing. The correlation between sea ice concentrations and sea ice drift is only robust for the central Weddell Sea, where both parameters are mainly anti-correlated. Hence, strong sea ice drift is connected to lower sea ice concentrations and vice versa. This finding is consistent with the connection to the wind fields, since stronger northerly winds would reduce the north-eastward drift of sea ice in this region and enhance the sea ice concentrations. From model simulations with FESOM it was found that sea ice thicknesses predominantly show the same tendencies for changes as the simulated sea ice concentrations, which are basically decreasing in the central Weddell Sea and increasing in the eastern Weddell Sea. The overall changes in sea ice thickness and concentration result in an increase of the total sea ice volume by 1 % per decade in the simulations. A sensitivity study with a free drift model, forced by 10-m wind speeds and ocean currents from FESOM showed that the trends in the modelled sea ice drift are driven by the atmospheric fields, since ocean currents show barely any trends. Further it was revealed that sea ice drift velocities in the model are overestimated, especially in the zonal direction. Nevertheless, despite the overestimation, the mean sea ice export rate of 22 x 10^3 m^3/s is only about half of the export rates found in previous studies, which is certainly an effect of underestimated sea ice thicknesses in the western Weddell Sea

Identification of genes involved in macrophage activation and effector functions against intracellular pathogens

Includes bibliographical references.This dissertation addressed the hypothesis that macrophages have an alternative killing mechanism that is independent of superoxide and nitric oxide but dependent on IFN-γ, TNF and C/EBPβ. Since the mechanism and the genes involved in this alternative pathway are mostly unknown, the aim of this dissertation was to identify these macrophage effector genes and to functionally characterize their role during infection utilizing gene deficient mouse models. Since mice deficient for C/EBPβ (C/EBPβ-/-) expressed normal levels of IFN-y and TNF during Listeria monocytogenes infection, the macrophage effector genes involved in confinement and killing of L. monocytogenes were postulated to be downstream of C/EBPβ. Furthermore, C/EBPβ-/- mice are highly susceptible L. monocytogenes due to impaired listericidal activity. Comparison of the gene expression profiles of WT and C/EBPβ-/- macrophages infected with L. monocytogenes was postulated to increase the probability of identifying these effector genes, which would be differentially expressed between the two groups. Comparative gene expression profiling by DNA microarrays between L. monocytogenes in infected WT and C/EBPβ-/- macrophages, successfully identified 1268 genes to be differentially expressed between the two groups. A focussed functional clustering strategy reduced the number of candidate genes to 220. PKCδ was selected for further study since it was involved in humoral defense, immune signalling, production of superoxide, regulation of transcription and may be putatively transcriptionally regulated by C/EBPβ. Furthermore, PKCδ was indirectly shown to promote L. monocytogenes escape from the phagosome and to negatively regulate transcription activity of C/EBPβ. In addition, since PKCδ was un-regulated, as shown by microarray and confirmed by RT-PCR, in L. monocytogenes infected C/EBPβ-/- macrophages, it was therefore thought to play a detrimental role during L. monocytogenes. However, since this premise has never been investigated directly, the role PKCδ during innate immunity against L monocytogenes was examined using the PKCδ deficient (PKCδ-/-) mouse model. Data in this dissertation provides new insight into the role of PKCδ during innate immunity to L. monocytogenes. PKCδ-/- mice were highly susceptible to L. monocytogenes due to enhanced listerial escape and impaired listericidal activity. Despite full macrophage activation and production of nitric oxide, PKCδ-/- mice displayed uncontrolled bacterial growth and dissemination of L. monocytogenes, which led to early death of the mice. In contrast, PKCδ-/- mice were able to control Mycobacterium infection as well as WT mice, suggesting that the activity of PKCδ may be negatively regulated by L. monocytogenes. A systems biology approach generated the hypothesis that PKCδ may promote Rab5a activation, which together with localized release of superoxide into the phagosome and activation of C/EBPβ by PKCδ, resulted in the confinement of the L. monocytogenes within the phagosome. Alternatively, PKCδ may act in a separate pathway that confines L monocytogenes within the phagosome, by activating and/or synergizing with unidentified proteins to neutralize that activity of listerial LLO and PI-PLC. Data in this dissertation clearly demonstrates that PKCδ is critical for confinement of L monocytogenes within phagosomes and may be part of a listericidal mechanism that is independent or nitric oxide, superoxide and pro-inflammatory cytokines

Structure and stability of a high-coverage (1x1) oxygen phase on Ru(0001)

The formation of chemisorbed O-phases on Ru(0001) by exposure to O_2 at low pressures is apparently limited to coverages Theta <= 0.5. Using low-energy electron diffraction and density functional theory we show that this restriction is caused by kinetic hindering and that a dense O overlayer (Theta = 1) can be formed with a (1x1) periodicity. The structural and energetic properties of this new adsorbate phase are analyzed and discussed in view of attempts to bridge the so-called "pressure gap" in heterogeneous catalysis. It is argued that the identified system actuates the unusually high rate of oxidizing reactions at Ru surfaces under high oxygen pressure conditions.Comment: RevTeX, 6 pages, 3 figures, to appear in Phys. Rev. Let

Integration der Prozeßorientierung in das objektorientierte Paradigma:Klassenzuordnungsansatz vs. Prozeßklassenansatz

In den aktuell verfügbaren Methoden zur objektorientierten Softwareentwicklung wird der Modellierung und Implementierung von Geschäftsprozessen nur eine geringe oder keine Bedeutung beigemessen. Daraus resultiert das Problem, daß Anforderungen durch neue oder geänderte Geschäftsprozesse nicht direkt, d. h. ohne Methodenbruch, in die objektorientierte Softwareentwicklung einfließen können. Basierend auf dieser Erkenntnis wird ein Ansatz vorgestellt, der darauf abzielt, durch die explizite Berücksichtigung von Geschäftsprozessen und durch eine Trennung von Objekt- und Prozeßwissen, die Anpaßbarkeit und Erweiterbarkeit objektorientierter Informationssysteme zu steigern.<br/

The Adsorption of Atomic Nitrogen on Ru(0001): Geometry and Energetics

The local adsorption geometries of the (2x2)-N and the (sqrt(3)x sqrt(3))R30^o -N phases on the Ru(0001) surface are determined by analyzing low-energy electron diffraction (LEED) intensity data. For both phases, nitrogen occupies the threefold hcp site. The nitrogen sinks deeply into the top Ru layer resulting in a N-Ru interlayer distance of 1.05 AA and 1.10 AA in the (2x2) and the (sqrt(3)x sqrt(3))R30^o unit cell, respectively. This result is attributed to a strong N binding to the Ru surface (Ru--N bond length = 1.93 AA) in both phases as also evidenced by ab-initio calculations which revealed binding energies of 5.82 eV and 5.59 eV, respectively.Comment: 17 pages, 5 figures. Submitted to Chem. Phys. Lett. (October 10, 1996

A Method and Tool for Predictive Event-Driven Process Analytics

Business value can be lost if a decision maker’s action distance to the observation of a business event is too high. So far, two classes of information systems, which promise to assist decision makers, have been discussed independently from each other only: business intelligence systems that query historic business event data in order to prepare predictions of future process behavior and real-time monitoring systems. This paper suggests using real-time data for predictions following an event-driven approach. A predictive event-driven process analytics (edPA) method is presented which integrates aspects from business activity monitoring and process intelligence. Needs for procedure integration, metric quality, and the inclusion of actionable improvements are outlined. The method is implemented in the form of a software prototype and evaluated

The role of structural changes in the excitation of chemical waves in the system Rh(110)/NO+H₂

Previous investigations have demonstrated that the formation of chemical waves in the NO+H2 reaction on Rh(110) involves a cyclic transformation of the surface structure via various N,O-induced reconstructions, i.e., starting form the c(2×6)-O a cycle is initiated comprising the formation of a (2×3)/(3×1)-N and a mixed c(2×4)-2O,N structure. The stability and reactivity of these structures has been investigated in titration experiments as well as under stationary reaction conditions employing LEED, work function, rate measurements, and thermal desorption spectroscopy. It was shown that the c(2×6)-O and c(2×4)-2O,N structures exhibit a low reactivity whereas the (2×1)/(2×1)-N displays only a small to moderate decrease in catalytic activity (≈20%–30%) compared to the clean surface. On the basis of these results, an excitation mechanism for pulses in the NO+H2 reaction on Rh(110) was constructed consisting of the sequence c(2×6)-O, (2×1)/(3×1)-N c(2×4)-2O,N, c(2×6)-O

Kann die EU die NATO auf dem Balkan ersetzen?

Seit dem Regierungsantritt von George W. Bush und als Folge der Attentate vom 11. September 2001 mehren sich die Anzeichen dafür, daß sich die USA möglichst bald aus den militärischen Friedensmissionen auf dem Balkan zurückziehen wollen. Für diesen Fall stellt sich die Frage, ob die Missionen auch ohne amerikanischen Beitrag NATO-Operationen bleiben oder in die Verantwortung der Europäischen Union (EU) überführt werden sollten. Die Analyse zeigt zunächst, daß die Friedensmissionen auf dem Balkan noch auf absehbare Zeit eine umfassende militärische Präsenz benötigen. Die Beteiligten müssen mit Hilfe dieser Präsenz noch einige Jahre lang in der Lage sein, Unterstützungsaufgaben in der Region wahrzunehmen und Agitation gegen die Friedensabkommen zu unterbinden. Gemäß NATO-Einschätzung bleibt für 2003 eine breitflächige Anwesenheit größerer Kontingente im Verbund mit schnell verfügbaren Reservekräften in der Gesamtstärke von 45.000 Soldaten erforderlich. Was den Umfang und die meisten Fähigkeiten anbelangt, wären die EU-Europäer schon heute in der Lage, den amerikanischen Anteil an den Friedensoperationen zu ersetzen. Dies könnte allerdings nicht immer auf gleichwertigem Niveau geschehen und würde beispielsweise im Bereich der Führungsinformationssysteme zusätzliche Investitionen erfordern, um vor allem die nötige Durchhaltefähigkeit zu sichern. Insgesamt würde die EU für einige Jahre auf die Nutzung von Planungskapazitäten, Fähigkeiten und Mittel der NATO angewiesen bleiben. Unter den gegenwärtigen Umständen ist die EU nicht in der Lage, die politische Führung von KFOR und SFOR zu übernehmen. Nicht zuletzt blockieren Meinungsverschiedenheiten zwischen der Türkei und Griechenland über die Konsultationsmechanismen zwischen der Türkei und der EU im Falle EU-geführter Operationen eine gültige Vereinbarung zwischen der Allianz und der EU zur gemeinsamen Nutzung entsprechender NATO-Ressourcen. Als Alternative bleibt den EU-Staaten die Möglichkeit, eine »Europäisierung« innerhalb der NATO anzustreben. Eine solche Lösung würde die Anwendung des ESVP-Instrumentariums ausschließen und die politische Führung beim Nordatlantikrat der NATO belassen. Gleichzeitig hätte sie gegenüber einer EU-geführten Operation verschiedene Vorteile, die besonders für jene EU-Staaten von Bedeutung sind, die auch Mitglied der Allianz sind und in beiden Organisationen politische Mitsprache besitzen. Dazu gehört die unveränderte politische Einbindung der USA in den Verlauf des Friedensprozesses bei stärkerer europäischer Kontrolle der militärischen Operationen, eine Schonung knapper Ressourcen durch anhaltende Nutzung von Schlüsselfähigkeiten der USA und der Allianz sowie mehr Zeit, um die Defizite bei den relevanten europäischen Fähigkeiten zu beseitigen

Depth information in natural environments derived from optic flow by insect motion detection system: a model analysis

Knowing the depth structure of the environment is crucial for moving animals in many behavioral contexts, such as collision avoidance, targeting objects, or spatial navigation. An important source of depth information is motion parallax. This powerful cue is generated on the eyes during translatory self-motion with the retinal images of nearby objects moving faster than those of distant ones. To investigate how the visual motion pathway represents motion-based depth information we analyzed its responses to image sequences recorded in natural cluttered environments with a wide range of depth structures. The analysis was done on the basis of an experimentally validated model of the visual motion pathway of insects, with its core elements being correlation-type elementary motion detectors (EMDs). It is the key result of our analysis that the absolute EMD responses, i.e. the motion energy profile, represent the contrast-weighted nearness of environmental structures during translatory self-motion at a roughly constant velocity. In other words, the output of the EMD array highlights contours of nearby objects. This conclusion is largely independent of the scale over which EMDs are spatially pooled and was corroborated by scrutinizing the motion energy profile after eliminating the depth structure from the natural image sequences. Hence, the well-established dependence of correlation-type EMDs on both velocity and textural properties of motion stimuli appears to be advantageous for representing behaviorally relevant information about the environment in a computationally parsimonious way