Recent results of H-mode studies on asdex

In a comparative study of various confinement regimes the H-mode demonstrated the best performance. Confinement enhancement factors (above ITER 89-P L-mode scaling) in the range of 1.6 fH 2.8 have been achieved with values depending on the divertor configuration, the wall condition, ELM behaviour and the plasma ion spicies. Long-pulse H-phases, withELMs, of up to 3.5s with constant confinement time, recycling and impurity characteristics are archived. H* -mode operation is possible without a loss of current scaling at qa values as low as 2.2. The B-limit is the same with and without ELMs. Murakami parameters are similar in H-and L-modes

On the mutual effect of ion temperature gradient instabilities and impurity peaking in the reversed field pinch

The presence of impurities is considered in gyrokinetic calculations of ion temperature gradient (ITG) instabilities and turbulence in the reversed field pinch device RFX-mod. This device usually exhibits hollow Carbon/Oxygen profiles, peaked in the outer core region. We describe the role of the impurities in ITG mode destabilization, and analyze whether ITG turbulence is compatible with their experimental gradients.Comment: 19 pages, 9 figures, accepted for publication in Plasma Phys. Control. Fusio

Rapid contemporary evolution and clonal food web dynamics

Character evolution that affects ecological community interactions often occurs contemporaneously with temporal changes in population size, potentially altering the very nature of those dynamics. Such eco-evolutionary processes may be most readily explored in systems with short generations and simple genetics. Asexual and cyclically parthenogenetic organisms such as microalgae, cladocerans, and rotifers, which frequently dominate freshwater plankton communities, meet these requirements. Multiple clonal lines can coexist within each species over extended periods, until either fixation occurs or a sexual phase reshuffles the genetic material. When clones differ in traits affecting interspecific interactions, within-species clonal dynamics can have major effects on the population dynamics. We first consider a simple predator-prey system with two prey genotypes, parameterized with data on a well-studied experimental system, and explore how the extent of differences in defense against predation within the prey population determine dynamic stability versus instability of the system. We then explore how increased potential for evolution affects the community dynamics in a more general community model with multiple predator and multiple prey genotypes. These examples illustrate how microevolutionary "details" that enhance or limit the potential for heritable phenotypic change can have significant effects on contemporaneous community-level dynamics and the persistence and coexistence of species.Comment: 30 pages, 6 Figure

Experimental determination of the transient transport and of fluctuations relevant to transport in ASDEX

Particle transport was studied in ASDEZ with modulated puffing of the discharge gas and of impurities. The energy transport is investigated by numerical simulation of the heat pulse after the swatooth crash. Small scale density fluctuations are investigated in the confinement region with far infrared scattering and reflectometry and in the edge plasma with langmuir probes and Ha diagnostic. In addition to a diffuse component of the particle transport, a strong inward drift is observed in all discharges. In ohmic discharges the transport coefficients decrease and saturate like 1/TE with increasing density. They are smaller in deuterium that in hydrogen. In the improved ohmic confinement (IOC)regime mainly D in the outer region is reduced. D increases proportionally to the heating power in L-mode discharges. The improvement of particle confinement in the H-mode is explained by a increase of the inward drift at the edge rather than a decrease of D. The impurity diffusion coefficient is independent of the impurity mass and charge. In ohmic discharges, it varies with ne like the bulk diffusion coefficient, is independent of B or increases weakly with B and increases with Ip. In L-mode discharges, Dimp increases linearly with the heating power. The electron thermal condustivity determined by heat pulse propagation exceeds the stationary value by a factor of 3-4, assuming merely diffusive heat transport. Convection does not significantly reduce this factor. however, non-diagonal terms

Adaptive Evolution in Ecological Communities

Multi-species interactions can influence evolution in ways that are unpredictable from studies that focus on simpler communities because direct and indirect species interactions alter the strength and direction of selection