Overseas Church and Missionary Directory

https://digitalcommons.acu.edu/crs_books/1217/thumbnail.jp

Contact-controlled amoeboid motility induces dynamic cell trapping in 3D-microstructured surfaces.

On flat substrates, several cell types exhibit amoeboid migration, which is characterized by restless stochastic successions of pseudopod protrusions. The orientation and frequency of new membrane protrusions characterize efficient search modes, which can respond to external chemical stimuli as observed during chemotaxis in amoebae. To quantify the influence of mechanical stimuli induced by surface topography on the migration modes of the amoeboid model organism Dictyostelium discoideum, we apply high resolution motion analysis in microfabricated pillar arrays of defined density and geometry. Cell motion is analyzed by a two-state motility-model, distinguishing directed cellular runs from phases of isotropic migration that are characterized by randomly oriented cellular protrusions. Cells lacking myosin II or cells deprived of microtubules show significantly different behavior concerning migration velocities and migrational angle distribution, without pronounced attraction to pillars. We conclude that microtubules enhance cellular ability to react with external 3D structures. Our experiments on wild-type cells show that the switching from randomly formed pseudopods to a stabilized leading pseudopod is triggered by contact with surface structures. These alternating processes guide cells according to the available surface in their 3D environment, which we observed dynamically and in steady-state situations. As a consequence, cells perform "home-runs" in low-density pillar arrays, crawling from pillar to pillar, with a characteristic dwell time of 75 s. At the boundary between a flat surface and a 3D structured substrate, cells preferentially localize in contact with micropillars, due to the additionally available surface in the microstructured arrays. Such responses of cell motility to microstructures might open new possibilities for cell sorting in surface structured arrays

Initial Public Offerings and Venture Capital in Germany

We present a survey on the role of initial public offerings (IPOs) and venture capital (VC) in Germany after the Second World War. Between 1945 and 1983 IPOs hardly played a role at all and only a minor role thereafter. In addition, companies that chose an IPO were much older and larger than the average companies going public for the first time in the US or the UK. The level of IPO underpricing in Germany, in contrast, has not been fundamentally different from that in other countries. The picture for venture capital financing is not much different from that provided by IPOs in Germany. For a long time venture capital financing was hardly significant, particularly as a source of early stage financing. The unprecedented boom on the Neuer Markt between 1997 and 2000, when many small venture capital financed firms entered the market, provides a striking contrast to the preceding era. However, by US standards, the levels of both IPO and venture capital activities remained rather low even in this boom phase. The extent to which recent developments will have a lasting impact on the financing of German firms, the level of IPO activity, and venture capital financing, remains to be seen. At the time of writing, activity has come to a near stand still and the Neuer Markt has just been dissolved. The low number of IPOs and the fairly low volume of VC financing in Germany before the introduction of the Neuer Markt are a striking and much debated phenomenon. Understanding the reasons for these apparent peculiarities is vital to understanding the German financial system. The potential explanations that have been put forward range from differences in mentality to legal and institutional impediments and the availability of alternative sources of financing. Moreover the recent literature discusses how interest groups may have benefited and influenced the situation. These groups include politicians, unions/workers, managers/controlling-owners of established firms as well as banks.Initial Public Offering (IPO), Venture Capital, Germany

The Role of Expectations in Economic Fluctuations and the Efficacy of Monetary Policy

We show diverse beliefs is an important propagation mechanism of fluctuations, money non neutrality and efficacy of monetary policy. Since expectations affect demand, our theory shows economic fluctuations are mostly driven by varying demand not supply shocks. Using a competitive model with flexible prices in which agents hold Rational Belief (see Kurz (1994)) we show that (i) our economy replicates well the empirical record of fluctuations in the U.S. (ii) Under monetary rules without discretion, monetary policy has a strong stabilization effect and an aggressive anti-inflationary policy can reduce inflation volatility to zero. (iii) The statistical Phillips Curve changes substantially with policy instruments and activist policy rules render it vertical. (iv) Although prices are flexible, money shocks result in less than proportional changes in inflation hence the aggregate price level appears “sticky” with respect to money shocks. (v) Discretion in monetary policy adds a random element to policy and increases volatility. The impact of discretion on the efficacy of policy depends upon the structure of market beliefs about future discretionary decisions. We study two rationalizable beliefs. In one case, market beliefs weaken the effect of policy and in the second, beliefs bolster policy outcomes and discretion could be a desirable attribute of the policy rule. Since the central bank does not know any more than the private sector, real social gain from discretion arise only in extraordinary cases. Hence, the weight of the argument leads us to conclude that bank’s policy should be transparent and abandon discretion except for rare and unusual circumstances. (vi) An implication of our model suggests the current effective policy is only mildly activist and aims mostly to target inflation.Monetary policy rules, Money non neutrality, Business cycles, Market volatility, Propagation mechanism, Capacity utilization, Heterogenous beliefs, Over confidence, Rational Belief, Optimism, Pessimism, Non stationarity, Empirical distribution

Contact Manifolds, Contact Instantons, and Twistor Geometry

Recently, Kallen and Zabzine computed the partition function of a twisted supersymmetric Yang-Mills theory on the five-dimensional sphere using localisation techniques. Key to their construction is a five-dimensional generalisation of the instanton equation to which they refer as the contact instanton equation. Subject of this article is the twistor construction of this equation when formulated on K-contact manifolds and the discussion of its integrability properties. We also present certain extensions to higher dimensions and supersymmetric generalisations.Comment: v3: 28 pages, clarifications and references added, version to appear in JHE