Ansätze zur Ordnungsreduktion von nichtlinearen Oszillatormodellen zur Anwendung im Schaltungsentwurf

Im Rahmen dieser Arbeit wird ein Konzept zur Ordnungsreduktion von höherdimensionalen nichtlinearen Oszillatormodellen vorgestellt. Hierbei werden zwei wesentliche Ziele verfolgt. Zum einen wird eine höherdimensionale Modellierung der Oszillatorschaltung verwendet. Hierdurch lassen sich die Einflüsse parasitärer Effekte sowie struktureller Erweiterungen auf das dynamische Verhalten des Systems berücksichtigen. Zum anderen wird durch eine anschließende Ordnungsreduktion über die Methode der Zentrumsmannigfaltigkeit eine zweidimensionale Systembeschreibung erzeugt, deren wesentliche Dynamik derjenigen des höherdimensionalen Systems entspricht. Durch diese, in der Ordnung reduzierte, nichtlineare und parameterabhängige Systembeschreibung wird die Anwendbarkeit nichtlinearer Analysemethoden ermöglicht bzw. vereinfacht. Mit der Anwendung der Andronov-Hopf-Bifurkationsanalyse auf das reduzierte System lässt sich eine Stabilitätsuntersuchung durchführen sowie die Amplitude und Frequenz aller Zustandsgrößen approximieren. Das vorgestellte Konzept wird anhand des Beispielsystems eines LC-Tank-VCOs durchgeführt. <br><br> In this paper, an order reduction technique for higher-dimensional nonlinear oscillator models, based on a center manifold approach, is presented. By modeling the oscillator circuit in the higher-dimensional state space, influences of parasitic elements and of structural extensions of the oscillator architecture on the dynamical system behavior can be examined. Using the proposed order reduction technique, a generalized second order model will be derived, which includes selected design parameters of the higher order model. By using an Andronov-Hopf bifurcation analysis, the reduced system can be studied with respect to stability as well as the amplitude and frequency of the individual state variables. The concept is applied to the design of LC-tank VCOs

Reduced TCR-dependent activation through citrullination of a T-cell epitope enhances Th17 development by disruption of the STAT3/5 balance

Citrullination is a post-translational modification of arginine that commonly occurs in inflammatory tissues. Because T-cell receptor (TCR) signal quantity and quality can regulate T-cell differentiation, citrullination within a T-cell epitope has potential implications for T-cell effector function. Here, we investigated how citrullination of an immunedominant T-cell epitope affected Th17 development. Murine na¨ıve CD4+ T cells with a transgenic TCR recognising p89-103 of the G1 domain of aggrecan (agg) were co-cultured with syngeneic bone marrow-derived dendritic cells (BMDC) presenting the native or citrullinated peptides. In the presence of pro-Th17 cytokines, the peptide citrullinated on residue 93 (R93Cit) significantly enhanced Th17 development whilst impairing the Th2 response, compared to the native peptide. T cells responding to R93Cit produced less IL-2, expressed lower levels of the IL-2 receptor subunit CD25, and showed reduced STAT5 phosphorylation, whilst STAT3 activation was unaltered. IL-2 blockade in native p89-103-primed T cells enhanced the phosphorylated STAT3/STAT5 ratio, and concomitantly enhanced Th17 development. Our data illustrate how a post-translational modification of a TCR contact point may promote Th17 development by altering the balance between STAT5 and STAT3 activation in responding T cells, and provide new insight into how protein citrullination may influence effector Th-cell development in inflammatory disorders

Adaptation to toposequence land types in West Africa of different sorghum genotypes in comparison with local cultivars of sorghum, millet, and maize

Gently undulating landscapes are typical for large parts of the Sudanian and Sahelian zones of the West African semiarid tropics. Within this landscape a pattern of land types and soils, which is closely linked to the topography, can be distinguished. Thus low fertility drought sensitive soils (Alfisols) are found on uplands, whereas the more fertile soils of the lower slopes and lowlands (mainly Inceptisols) will be moist to wet. In response to these variations in land types and the unpredictable rainfall, which can cause both droughts and floods during the rainy season, the subsistence farmers have adopted distinct cropping patterns in order to minimize the risk of crop failure under the conditions of a low input agriculture. Consequently, cropping patterns which closely follow the toposequence have evolved, with millets grown on dry uplands and slopes, maize on moist lower slopes, sorghum on lower slopes, and rice on lowlands. The present study was conducted mainly in Upper Volta and provides a scientific basis for these cropping patterns by analysing the responses of three major cereal crops to land types and to sowing dates. Next, several high yielding, introduced, sorghum cultivars were tested to determine their adaptation to the local conditions and to formulate plant characteristics useful to plant breeders in selecting improved cultivars which would best meet the requirements of the local agriculture. It was concluded that to meet the large diversity in land types and rainfall conditions typical for the West African semiarid tropics, even an advanced type agriculture would require a range of technological options, in terms of improved varieties and cultural practices. Consequently, the likelihood that a single improved cultivar could replace the local cultivars is remote, as is the possibility of introducing a standard technological package

Home country advantage? The influence of Italian, German and Austrian employee representatives in the UniCredit European Works Council

This article examines the first European Works Council (EWC) to be established in the Italian banking sector, at UniCredit. It focuses on the interaction between Italian, German and Austrian delegations of employee representatives and on the perspectives and practices that reflect their different cultural and institutional backgrounds in industrial relations. Much of the literature suggests that employee representatives from the home country of a multinational company are likely to mould EWC structures in accordance with their own national backgrounds and have greater confidence in dealing with central management in EWC meetings. Our findings partly substantiate this argument, but also suggest that minority delegations, when they have the benefit of strong national institutional arrangements and less fragmented union patterns, are more likely to be cohesive and experienced and therefore able to challenge management and sometimes win significant arguments over strategy

Traditional and Health-Related Philanthropy: The Role of Resources and Personality

I study the relationships of resources and personality characteristics to charitable giving, postmortem organ donation, and blood donation in a nationwide sample of persons in households in the Netherlands. I find that specific personality characteristics are related to specific types of giving: agreeableness to blood donation, empathic concern to charitable giving, and prosocial value orientation to postmortem organ donation. I find that giving has a consistently stronger relation to human and social capital than to personality. Human capital increases giving; social capital increases giving only when it is approved by others. Effects of prosocial personality characteristics decline at higher levels of these characteristics. Effects of empathic concern, helpfulness, and social value orientations on generosity are mediated by verbal proficiency and church attendance.

Coherent Stranski-Krastanov growth in 1+1 dimensions with anharmonic interactions: An equilibrium study

The formation of coherently strained three-dimensional islands on top of the wetting layer in Stranski-Krastanov mode of growth is considered in a model in 1+1 dimensions accounting for the anharmonicity and non-convexity of the real interatomic forces. It is shown that coherent 3D islands can be expected to form in compressed rather than in expanded overlayers beyond a critical lattice misfit. In the latter case the classical Stranski-Krastanov growth is expected to occur because the misfit dislocations can become energetically favored at smaller island sizes. The thermodynamic reason for coherent 3D islanding is the incomplete wetting owing to the weaker adhesion of the edge atoms. Monolayer height islands with a critical size appear as necessary precursors of the 3D islands. The latter explains the experimentally observed narrow size distribution of the 3D islands. The 2D-3D transformation takes place by consecutive rearrangements of mono- to bilayer, bi- to trilayer islands, etc., after exceeding the corresponding critical sizes. The rearrangements are initiated by nucleation events each next one requiring to overcome a lower energetic barrier. The model is in good qualitative agreement with available experimental observations.Comment: 12 pages text, 15 figures, Accepted in Phys.Rev.B, Vol.61, No2

A Full Computation-relevant Topological Dynamics Classification of Elementary Cellular Automata

Cellular automata are both computational and dynamical systems. We give a complete classification of the dynamic behaviour of elementary cellular automata (ECA) in terms of fundamental dynamic system notions such as sensitivity and chaoticity. The "complex" ECA emerge to be sensitive, but not chaotic and not eventually weakly periodic. Based on this classification, we conjecture that elementary cellular automata capable of carrying out complex computations, such as needed for Turing-universality, are at the "edge of chaos"