Lifetime of Kaonium

The kaon--antikaon system is studied in both the atomic and the strongly interacting sector. We discuss the influence of the structures of the $f_0(980)$ and the $a_0(980)$ mesons on the lifetime of kaonium. The strong interactions are generated by vector meson exchange within the framework of the standard $SU(3)_V\times SU(3)_A$ invariant effective Lagrangian. In the atomic sector, the energy levels and decay widths of kaonium are determined by an eigenvalue equation of the Kudryavtsev--Popov type, with the strong interaction effects entering through the complex scattering length for $K\bar K$ scattering and annihilation. The presence of two scalar mesons, $f_0(980)$ and $a_0(980)$, leads to a ground state energy for the kaonium atom that is shifted above the point Coulomb value by a few hundred eV. The effect on the lifetime for the kaonium decay into two pions is much more dramatic. This lifetime is reduced by two orders of magnitude from $0.8\times 10^{-16}$ sec for annihilation in a pure Coulomb field down to $3.1\times 10^{-18}$ sec when the strong interactions are included. The analysis of the two photon decay width of the $f_0(980)$ suggests a generalization of the molecular picture which reduces the lifetime of kaonium still further to $1.1\times 10^{-18}\textrm{sec}$.Comment: 33 pages, 12 figures;3 new figures and new comment concerning the a

Guest editorial

PeerReviewe

Social Preferences, Skill Segregation and Wage Dynamics

We study the earning structure and the equilibrium asignment of workers to firms in a model in which workers have social preferences, and skills are perfectly substitutable in production. Firms offer long-term contracts, and we allow for frictions in the labour market in the form of mobility costs. The model delivers specific predictions about the nature of worker flows, about the characteristic of workplace skill segregation, and about wage dispersion both within and cross firms. We shows that long-term contracts in the resence of social preferences associate within-firm wage dispersion with novel "internal labour market" features such as gradual promotions, productivity-unrelated wage increases, and downward wage flexibility. These three dynamic features lead to productivity-unrelated wage volatily within firms.Publicad

Filling some black holes: modeling the connection between urbanization, infrastructure, and global service intensity

This empirical article combines insights from previous research on the level of knowledge-intensive service in metropolitan areas with the aim to develop an understanding of the spatial structure of the global service economy. We use a stepwise regression model with the Globalization and World Cities research network's measure of globalized service provisioning as the dependent variable and a range of variables focusing on population, infrastructure, urban primacy, and national regulation as independent variables. The discussion of the results focuses on model parameters as well as the meaning of outliers and is used to explore some avenues for future research

Mechanical efficiency of stunned myocardium is modulated by increased afterload dependency

Oxygen consumption (MVO2) of stunned myocardium is relatively high compared to, and poorly correlated with, systolic contractile function. The aim of this study was to investigate whether an increased afterload dependency, induced by the decreased contractility of the stunned myocardium, contributes to the large variability in the mechanical efficiency data. Methods: In 13 anaesthetised open thorax pigs undergoing two cycles of 10 min occlusion of left anterior descending coronary artery and 30 min reperfusion, segment shortening, the slope of end systolic pressure segment length relationship (Ees), external work (EW, derived from the area inside the left ventricular pressure segment length loop), the efficiency of energy conversion (EET, = Embedded Image × 100%, where PLA = total pressure-segment length area), mechanical efficiency (Embedded Image), and their dependency on left ventricular end systolic pressure (Pes) were determined before and after induction of stunning, and during subsequent inotropic stimulation with dobutamine (1 and 3 μg·kg−1·min−1 over 15 min). Results: The stunning protocol not only caused significant decreases in segment shortening, external work, energy conversion efficiency, and Embedded Image but also increased the afterload dependency of these variab Before stunning an increase in Pes from 100 to 160 mm Hg decreased segment shortening from 18(SEM 1)% to 14(2)% (P > 0.05) and increased external work from 206(18) to 254(32) mm Hg·mm (P < 0.05). After induction of stunning the same increase in Pes caused a decrease in segment shortening from 9.5(1.8)% to −4.6(2.1)% (P < 0.05) and in external work from 149(21) to −11(10) mm Hg·mm (P < 0.05). The afterload dependency of the PLA was not altered by stunning, but the afterload dependency of energy conversion efficiency increased, since efficiency decreased from 67(3)% to 59(5)% as Pes was increased from 100 to 160 mm Hg before stunning, but from 57(5) to −7(5)% after induction of stunning (P < 0.05). Furthermore, the same increase in Pes resulted in an 8% decrease of Embedded Image before stunning and 107% after inducti stunning. Infusion of dobutamine not only restored segment shortening, external work, energy conversion efficiency, and Embedded Image of the stunned myocardium, but also attenuated their afterload dependency to levels. Conclusions: Myocardial stunning increases the afterload dependency of segment shortening, external work, energy conversion efficiency, and mechanical efficiency, which can be attenuated by inotropic stimulation with dobutamine. However, the decrease in left ventricular end systolic pressure, which accompanies the induction of stunning, counteracts the decrease in these variables. These two mechanisms can explain most of the reported scatter in mechanical efficiency

Meson model for f_0(980) production in peripheral pion-nucleon reactions

The Juelich model for pion-pion-scattering, based on an effective meson-meson Lagrangian is applied to the analysis of the S-wave production amplitudes derived from the BNL E852 experiment pi^- p -> pi^0 pi^0 n for a pion momentum of 18.3 GeV. The unexpected strong dependence of the S-wave partial wave amplitude on the momentum transfer between the proton and neutron in the vicinity of the f_0(980) resonance is explained in our analysis as interference effect between the correlated and uncorrelated pi^0 pi^0 pairs.Comment: 6 pages, 7 figures, formulas added, typos removed, new figure

Exploring the role of professional associations in collective learning in London and New York's advertising and law professional service firm clusters.

The value of regional economies for collective learning has been reported by numerous scholars. However often work has been criticised for lacking analytical clarity and failing to explore the architectures of collective learning and the role of the knowledge produced in making firms in a cluster economy successful. This paper engages with these problematics and investigates how collective learning is facilitated in the advertising and law professional service firm clusters in London and New York. It explores the role of professional associations and investigates how they mediate a collective learning process in each city. It argues that professional associations seed urban communities of practice that emerge outside of the formal activities of professional associations. In these communities individual with shared interests in advertising and law learn from one-another and are therefore able to adapt and evolve one-another approaches to common industry challenges. The paper suggests this is another form of the variation Marshall highlighted in relation to cluster-based collective learning. The paper also shows how the collective learning process is affected by the presence, absence and strength of an institutional thickness. It is therefore argued that a richer understanding of institutional affects is needed in relation to CL