Left ventricular active stiffness: dependency on time and inotropic state

Left ventricular systolic stiffness was measured by rapidly changing ventricular volume (within 7 ms) of isovolumically contracting isolated rabbit hearts. Instantaneous pressure-volume relations were found to be linear with slopes that depended upon the moment during contraction at which the volume change was induced. These slopes were proportional to the total pressure developed in the ventricle just prior to the volume change. The same was found when the time course of pressure was influenced by changing the Ca++ content of the perfusate. An influence, however, also could be detected when end-diastolic volume was changed. At the same pre-release pressure a greater volume caused a decrease of active stiffness. The results indicate the possiblity of an active component in ventricular systolic stiffness

Left ventricular force-velocity relations measured from quick volume changes

Left ventricles of rabbit hearts were subjected to series of quick volume releases (QVR) — taking placw within 6 ms — applied at fixed times in the cardiac cycle. The hearts were paced artificially and allowed to contract isovolumically. The QVR was used as a tool for realizing predetermined pressure values at any time during the ascending limb of the intra-ventricular pressure curve. Any desired pressure could be attained by suitable choice of the QVR amplitude. By relatingdP/dt values occuring immediately after the QVR to the pressure attained by the QVR for different QVR amplitudes, instantaneousdP/dt relations were obtained. Time effects on these relations were studied by repeating the QVR series with increasing amplitudes at different but constant times. Influences of volume and contractile state were examined by varying end diastolic pressure (EDP) and the perfusate [Ca2+]. The data were fitted with adP/dt-P relation derived from the Hill equation using a simple geometric model of the ventricle and a two element model of the myocardium. The experimental relations were described adequately by the model. The parameters in the Hill equation estimated for heart muscle were compared to those previously reported on heart muscle experiments. Parameter values obtained were:a/F0: 0.001–1.3;F0 (mean maximal force forVCE=0): 12.2-3.5 N;b: 1.7–13.2 cm/s.F0 rises at the beginning of systole and shows a plateau from ca. 60–100% time of peak pressure. This time course was influenced by changes in EDP and [Ca2+]. Parameterb exhibits a time course comparable to that of ventricular pressure. It was not influenced by EDP changes and only slightly increased by an increase in [Ca2+]

M&A in the Construction Industry -Wealth Effects of Diversification into Real Estate Life Cycle Related Services

Since the late 1990s, the construction industry has undergone a change in business model, as contractors vertically expand their operations to other parts of the real estate life cycle. The question arises on whether construction companies have superior abilities as real estate service providers. We have examined the value implications of 106 large merger and acquisition (M&A) transactions in the construction industry worldwide from 1986 to 2006. We inquire if a vertical expansion of the construction value chain in the real estate life cycle through M&A leads to the creation of shareholder value. We find out that this is not the case. M&A success is mainly determined by industry-specific size effects and common agency conflicts.Construction industry; Cross-border acquisitions; Bidder gains; Global diversification

Consolidation and Market Power of Energy Utilities - The case of US-American and German Utility Takeovers

Between 1990 and 2002 a wave of takeovers was observed in the North American and European energy utilities market. We analyze the impact of these takeovers on market power, studying 70 takeovers of US-American and 69 takeovers of German energy utilities by applying event study methodology. Stock price reactions of acquiring and target firms as well as of their competitors are used as an indicator for market power. While we do not find any significant results pointing in this direction for transactions in the US, our findings clearly indicate that the potential to increase market power is indeed an important motive for takeovers within the German energy utilities market.acquisitions, energy utilities, market power, oligopoly, regulation

Postcard: Wedge Snow Plow at Work #1X

This black and white photographic postcard depicts a train pushing snow off the train tracks. The train plowed into the snow to the point that the front of the train cannot be seen. Snow flies up left and right and fills the center of the photo. Written text is at the top of the card. Handwriting is on the back of the card.https://scholars.fhsu.edu/tj_postcards/2294/thumbnail.jp

Wilson loops, instantons and quantum mechanics

In this thesis we will examine two different problems. The first is the computation of vacuum expectation values of Wilson loop operators in ABJM theory, the other problem is finding the instanton series of the refined topological string on certain local Calabi-Yau geometries in the Nekrasov-Shatashvili limit. Based on the description of ABJM theory as a matrix model, it is possible to find a description of it in terms of an ideal Fermi gas with a non-trivial one-particle Hamiltonian. The vacuum-expectation-values of Wilson loop operators in ABJM theory correspond to averages of operators in the statistical-mechanical problem. Using the WKB expansion, it is possible to extract the full 1/N expansion of the vevs, up to exponentially small contributions, for arbitrary Chern-Simons coupling. We will compute these vevs for the 1/6 and 1/2 BPS Wilson loops at any winding number. These can be written in terms of the Airy function. The expressions we found reproduce the low genus results previously obtained in the 't Hooft expansion. In another problem we use mirror symmetry, quantum geometry and modularity properties of elliptic curves to calculate the refined free energies, given in terms of an instanton sum, in the Nekrasov-Shatashvili limit on non-compact toric Calabi-Yau manifolds, based on del Pezzo surfaces. Quantum geometry here is to be understood as a quantum deformed version of rigid special geometry, which has its origin in the quantum mechanical behavior of branes in the topological string B-model. We will argue that in the Seiberg-Witten picture only the Coulomb parameters lead to quantum corrections, while the mass parameters remain uncorrected. In certain cases we will also compute the expansion of the free energies at the orbifold point and the conifold locus. We will compute the quantum corrections order by order on ħ by deriving second order differential operators, which act on the classical periods

Kontrolldefizite bei den Kapitalbeteiligungsgesellschaften der Sparkassen

In den letzten Jahren haben öffentlich-rechtliche Kreditinstitute zunehmend Kapitalbeteiligungsgesellschaften gegründet. Wie sind diese unter Corporate Governance Gesichtspunkten zu beurteilen? Gibt es Kontrolldefizite bei den Beteiligungsgesellschaften? Können dort anreizkompatible Überwachungsinstrumente zum Einsatz kommen? --