Proton-proton bremsstrahlung below and above pion-threshold: the influence of the Δ\Delta-isobar

The proton-proton bremsstrahlung is investigated within a coupled-channel model with the $\Delta$ degree of freedom. The model is consistent with the $NN$ scattering up to 1 GeV and the $\gamma N\Delta$ vertex determined in the study of pion photoproduction reactions. It is found that the $\Delta$ excitation can significantly improve the agreements with the $pp \rightarrow pp\gamma$ at $E_{lab}=280$ MeV. Predictions at $E_{lab}=550$ and $800$ MeV are presented for future experimental tests.Comment: 26 pages Revtex, 12 figures are available from the authors upon request ([email protected]

Evaluating application service provisioning using system dynamics methodology

Despite the hype surrounding the value-added potential of e-business for contemporary firms, the recent technology downturn was marked by poor customer satisfaction from investment in e-business initiatives. An apparent mismatch between customer expectations and vendor offerings suggested a lack of appropriate methods and techniques for evaluating e-business. This article draws from a longitudinal research study on the deployment, hosting and integration of application service provisioning (ASP), an e-business model targeted mainly at small and medium-sized businesses (SMBs). Using system dynamics as a methodology that addresses the inherent complexity of the ASP model, the article demonstrates how a series of complex interrelationships between key performance indicators (KPIs) will impact the business value for customers from ASP vendor products and services. The lessons from this research will be particularly relevant for existing and future ASP vendors and customers

Sex and age influence responses to changes in the cost of cooperative care in a social carnivore

In cooperative breeders, variation in contributions to offspring care will often be determined by variation in the cost of care. Because the cost of investment is determined by its effect on residual reproductive value, a unit of care should impose different fitness costs on different life-history categories of helper. This means that a change in current condition should have category-specific effects on contributions to care. I test this in the cooperatively breeding banded mongoose (Mungos mungo), experimentally increasing the cost of care by subjecting helpers to temporary deprivation. I observed category-specific effects on pup provisioning: For a given percentage weight loss, female helpers reduce their provisioning by a greater extent than male helpers. This is likely to be because variation in condition has a stronger effect on female reproductive success, so females should be under stronger selection to limit the cost of offspring care. I also observed an unexpected effect of age, with older helpers reducing their provisioning by more than younger helpers. This is probably because older helpers are more likely to breed themselves, so changes in condition may have a more immediate effect on direct fitness. In general, category-specific responses to changes in state should occur wherever there are existing category-specific differences in contributions to care, in both cooperative breeders and biparental species. Copyright 2010, Oxford University Press.