Formation of phase space holes and clumps.

It is shown that the formation of phase space holes and clumps in kinetically driven, dissipative systems is not restricted to the near threshold regime, as previously reported and widely believed. Specifically, we observe hole-clump generation from the edges of an unmodulated phase space plateau, created via excitation, phase mixing and subsequent dissipative decay of a linearly unstable bulk plasma mode in the electrostatic bump-on-tail model. This has now allowed us to elucidate the underlying physics of the hole-clump formation process for the first time. Holes and clumps develop from negative energy waves that arise due to the sharp gradients at the interface between the plateau and the nearly unperturbed, ambient distribution and destabilize in the presence of dissipation in the bulk plasma. We confirm this picture by demonstrating that the formation of such nonlinear structures in general does not rely on a "seed" wave, only on the ability of the system to generate a plateau. In addition, we observe repetitive cycles of plateau generation and erosion, the latter due to hole-clump formation and detachment, which appear to be insensitive to initial conditions and can persist for a long time. We present an intuitive discussion of why this continual regeneration occurs.

Patterns of invasive ctenophore Mnemiopsis leidyi distribution and variability in different recipient environments of the Eurasian seas: A review.

Harmful invader ctenophore Mnemiopsis leidyi's expansions in the Eurasian Seas, its spatio-temporal population dynamics depending on environmental conditions in recipient habitats have been synthesized. M. leidyi found suitable temperature, salinity and productivity conditions in the temperate and subtropical environments of the semi-enclosed seas, in the coastal areas of open basins and in closed water bodies, where it created autonomous populations. M. leidyi changes its phenology depending on seasonal temperature regime in different environments. We assessed ranges of sea surface temperature, sea surface salinity and sea surface chlorophyll values, sufficient for M. leidyi general occurrence and reproduction based on comprehensive long-term datasets, contributed by co-authors. This assessment revealed that there are at least two eco-types (Southern and Northern) in the recipient seas of Eurasia with features specific for their donor areas. The range of thresholds for M. leidyi establishment, occurrence and life cycle in both eco-types depends on variability of environmental parameters in their native habitats.

Antiasthmatic effects of a leukotriene biosynthesis inhibitor (MK-0591) in allergic dogs.

Peptidoleukotrienes may be important mediators of human bronchial asthma. Accordingly, the effects of a selective leukotriene (LT) biosynthesis inhibitor (MK-0591) were assessed in allergic dogs characterized by acute bronchoconstriction and subsequent airway hyperresponsiveness induced by inhaled ragweed allergen. Peak acute increases in airway resistance (Rrs) induced by ragweed were associated with increased bronchoalveolar lavage histamine concentration, and neither parameter was inhibited by MK-0591 (8 micrograms.kg-1.min-1 i.v.). However, the duration of the bronchoconstriction was significantly decreased by MK-0591, with a reduction in the area under the curve of 40% (P < 0.05). Associated with the acute bronchoconstriction in placebo-treated animals was a fivefold increase in urinary LTE4 excretion (as seen with allergic asthmatic patients), which was reduced to < 10% of basal values by MK-0591. Similarly, whole blood LTB4 biosynthesis was abolished in the MK-0591-treated animals. Bronchial hyperresponsiveness preallergen (measured as the percent concentration of acetylecholine required to increase Rrs by 5 cmH2O.l-1.s) tended to improve with MK-0591 (0.41 +/- 0.15 vs. 0.23 +/- 0.05%). Five hours after allergen inhalation, the percent concentration declined substantially in the placebo group (0.07 +/- 0.02%; P < 0.01), revealing an increased airway responsiveness that was significantly blunted by MK-0591 (0.26 +/- 0.07%; P < 0.001). These data suggest that selective inhibition of LT biosynthesis by novel compounds such as MK-0591 may modify the airway changes associated with bronchial hyperresponsiveness, as well as offer symptomatic relief in asthma.

Development of chronic airway hyperresponsiveness in ragweed-sensitized dogs.

We studied dogs neonatally sensitized to ragweed and their littermate controls at 4, 6, 8, 10, 12, and 15 mo of age. Acute allergic airway response to inhalation of ragweed in the sensitized dogs was marked (greater than 12-fold increase from base line) and reproducible at all times. Nonallergic airway responsiveness, measured as the concentration of acetylcholine required to increase airway resistance by 5 cmH2O.l-1.s (PC5), increased in sensitized and decreased in nonsensitized dogs from 4 to 15 mo of age (P less than 0.01). Before antigen, at 12 and 15 mo, sensitized dogs were significantly (P less than 0.05) more responsive to acetylcholine than controls. Six hours after antigen, sensitized dogs were 11-fold more responsive (P less than 0.005) than controls at those times. More eosinophils and mast cells and fewer macrophages (P less than 0.05) were present in bronchoalveolar lavage (BAL) from 12- and 15-mo-old sensitized dogs than their controls. BAL fluid histamine was higher (P less than 0.05) in sensitized than control dogs. Regression analysis revealed r = -0.75 (P = 0.003) between BAL mast cells and PC5 in sensitized dogs and R2 = 0.89 for PC5 and BAL mast cells, macrophages, and eosinophils. Neonatally sensitized dogs represent an excellent animal model in which to study the pathophysiology of asthma.

Destabilizing effect of dynamical friction on fast-particle-driven waves in a near-threshold nonlinear regime.

The nonlinear evolution of waves excited by the resonant interaction with energetic particles, just above the instability threshold, is shown to depend on the type of relaxation process that restores the unstable distribution function. When dynamical friction dominates over diffusion in the phase space region surrounding the wave-particle resonance, an explosive evolution of the wave is found to be the only solution. This is in contrast with the case of dominant diffusion when the wave may exhibit steady-state, amplitude modulation, chaotic and explosive regimes near marginal stability. The experimentally observed differences between Alfvénic instabilities driven by neutral beam injection and those driven by ion-cyclotron resonance heating are interpreted.