A Characterization of Consensus Solvability for Closed Message Adversaries

Distributed computations in a synchronous system prone to message loss can be modeled as a game between a (deterministic) distributed algorithm versus an omniscient message adversary. The latter determines, for each round, the directed communication graph that specifies which messages can reach their destination. Message adversary definitions range from oblivious ones, which pick the communication graphs arbitrarily from a given set of candidate graphs, to general message adversaries, which are specified by the set of sequences of communication graphs (called admissible communication patterns) that they may generate. This paper provides a complete characterization of consensus solvability for closed message adversaries, where every inadmissible communication pattern has a finite prefix that makes all (infinite) extensions of this prefix inadmissible. Whereas every oblivious message adversary is closed, there are also closed message adversaries that are not oblivious. We provide a tight non-topological, purely combinatorial characterization theorem, which reduces consensus solvability to a simple condition on prefixes of the communication patterns. Our result not only non-trivially generalizes the known combinatorial characterization of the consensus solvability for oblivious message adversaries by Coulouma, Godard, and Peters (Theor. Comput. Sci., 2015), but also provides the first combinatorial characterization for this important class of message adversaries that is formulated directly on the prefixes of the communication patterns

Numerical solution of optimal control problems with constant control delays

We investigate a class of optimal control problems that exhibit constant exogenously given delays in the control in the equation of motion of the differential states. Therefore, we formulate an exemplary optimal control problem with one stock and one control variable and review some analytic properties of an optimal solution. However, analytical considerations are quite limited in case of delayed optimal control problems. In order to overcome these limits, we reformulate the problem and apply direct numerical methods to calculate approximate solutions that give a better understanding of this class of optimization problems. In particular, we present two possibilities to reformulate the delayed optimal control problem into an instantaneous optimal control problem and show how these can be solved numerically with a state-of-the-art direct method by applying Bock’s direct multiple shooting algorithm. We further demonstrate the strength of our approach by two economic examples.delayed differential equations, delayed optimal control, numerical optimization, time-to-build

Religions / Reasons for and contexts of deep theological engagement with other religious traditions in Europe : toward a comparative theology

The different contexts of America and Europe have a significant impact on the development of comparative theology, especially in the German-speaking countries. The latter have found other solutions to the problem of religious pluralism that are not really conducive to comparative theology. Hence, the double responsibility of Catholic theology in particular toward the university and toward the Church is a part of the discourse policy of theology, which affects the theology of religions and comparative theology. On the one hand, theology is under the protection of the state, and on the other hand theology is threatened by the risk of unreliability due to ecclesiastical paternalism. But the theology of religions and comparative theology do not evade into science of religion or neo-orthodoxy, rather, they take a risk in a theological engagement with other religions, bringing ones own faith into a deep encounter with other religions and their faiths while delving into points of detail. After giving short descriptions of these tasks, this article shows some examples of practice in comparative theology and gives a prospect into potential further developments of comparative theology in theories of difference and spaces.(VLID)157534

Large variations in the hole spin splitting of quantum-wire subband edges

We study Zeeman splitting of zone-center subband edges in a cylindrical hole wire subject to a magnetic field parallel to its axis. The g-factor turns out to fluctuate strongly as a function of wire-subband index, assuming values that differ substantially from those found in higher-dimensional systems. We analyze the spin properties of hole-wire states using invariants of the spin-3/2 density matrix and find a strong correlation between g-factor value and the profile of hole-spin polarization density. Our results suggest possibilities for confinement engineering of hole spin splittings.Comment: 4 pages, 3 figures, RevTex4, to appear in PR

Static polarizability of two-dimensional hole gases

We have calculated the density-density (Lindhard) response function of a homogeneous two-dimensional (2D) hole gas in the static (omega=0) limit. The bulk valence-band structure comprising heavy-hole (HH) and light-hole (LH) states is modeled using Luttinger's kdotp approach within the axial approximation. We elucidate how, in contrast to the case of conduction electrons, the Lindhard function of 2D holes exhibits unique features associated with (i) the confinement-induced HH-LH energy splitting and (ii) the HH-LH mixing arising from the charge carriers' in-plane motion. Implications for the dielectric response and related physical observables are discussed.Comment: 11 pages, 3 figures, IOP latex style, v2: minor changes, to appear in NJ

Effects of androgens on haemostasis

Abstract Androgen deficiency is associated with an increased incidence of cardiovascular disease. There is evidence that thromboembolic disease as well as myocardial infarction in hypogonadic males are mediated by low baseline fibrinolytic activity. Hypogonadism in males is associated with an enhancement of fibrinolytic inhibition via increased synthesis of the plasminogen activator inhibitor PAl 1. On the other hand, stanozoiol and danazol reduce PAl 1 and are associated with increased fibrinolytic activity. However, in male abusers of anabolic steroids the net effect on the haemostatic system may change from anti-to prothrombotic; there appears to be an individual threshold dose above which thrombogenic effects on platelets and vasomotion may overcome the profibrinolytic effects on PAl 1. There are numerous reports on weight-lifters dying of atherothrombotic ischemic heart disease while abusing anabolic steroids. Androgens are known to have profound effects on carbohydrate and lipid metabolism. In fact, much of the individual inconsistency of the effects of androgens on fibrinolytic and haemostatic activity appears to be based on the close interrelationship of these metabolic systems. Androgens may have urifavourable effects on the HDL/LDL cholesterol ratio, on triglyceride levels and on the insulin/insulin-like growth factor 1 (IGF 1) system. Hypertriglyceridemia as well as insulin resistance are both associated with low fibrinolytic activity and increased PAl 1 levels. On the other hand, lipoprotein(a), a recently acknowledged independent risk factor of CVD was shown to respond favourable to androgen treatment, in men as well as in women. In women, agonistic as well as antagonistic effects of estrogens and progestins need to be taken into account. In fact, estradiol may modulate testosterone effects on haemostasis. Androgen medication in premenopausal women, such as danazol, was found to reduce PAI 1 suggesting an improvement of the fibrinolytic activity. Also, in hormone replacement therapy (HRT) androgenic progestins or complex compounds with androgenic effects are associated with a marked reduction of PAI 1 and an improvement of fibrinolytic activity. Further improvement of fibrinolytic activity may be associated with the marked decrease of lipoprotein (a) (Lp(a)) in women on androgenic HRT. However, little is known on the interrelationship of estrogens, 19-nortestosterone or progesterone derivatives and testosterone, an interrelationship that may have substantial impact on the metabolic and particularly haemostatic net effects of a preparation. In summary, information on the effects of androgens on haemostasis is limited and may be particularly incomplete due to the fact that interaction with other i Dedicated to Prof Dr med A.E. Schindler on the occasion of his 60th anniversary. 0378-5122/96/$15.0

Numerical Solution of Optimal Control Problems with Constant Control Delays

We investigate a class of optimal control problems that exhibit constant exogenously given delays in the control in the equation of motion of the differential states. Therefore, we formulate an exemplary optimal control problem with one stock and one control variable and review some analytic properties of an optimal solution. However, analytical considerations are quite limited in case of delayed optimal control problems. In order to overcome these limits, we reformulate the problem and apply direct numerical methods to calculate approximate solutions that give a better understanding of this class of optimization problems. In particular, we present two possibilities to reformulate the delayed optimal control problem into an instantaneous optimal control problem and show how these can be solved numerically with a state-of-the-art direct method by applying Bock's direct multiple shooting algorithm. We further demonstrate the strength of our approach by two economic example

Topological Characterization of Consensus Solvability in Directed Dynamic Networks

Consensus is one of the most fundamental problems in distributed computing. This paper studies the consensus problem in a synchronous dynamic directed network, in which communication is controlled by an oblivious message adversary. The question when consensus is possible in this model has already been studied thoroughly in the literature from a combinatorial perspective, and is known to be challenging. This paper presents a topological perspective on consensus solvability under oblivious message adversaries, which provides interesting new insights. Our main contribution is a topological characterization of consensus solvability, which also leads to explicit decision procedures. Our approach is based on the novel notion of a communication pseudosphere, which can be seen as the message-passing analog of the well-known standard chromatic subdivision for wait-free shared memory systems. We further push the elegance and expressiveness of the "geometric" reasoning enabled by the topological approach by dealing with uninterpreted complexes, which considerably reduce the size of the protocol complex, and by labeling facets with information flow arrows, which give an intuitive meaning to the implicit epistemic status of the faces in a protocol complex