Electron-acoustic plasma waves: oblique modulation and envelope solitons

Theoretical and numerical studies are presented of the amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, Boltzmann distributed hot electrons and stationary ions. Perturbations oblique to the carrier EAW propagation direction have been considered. The stability analysis, based on a nonlinear Schroedinger equation (NLSE), reveals that the EAW may become unstable; the stability criteria depend on the angle $\theta$ between the modulation and propagation directions. Different types of localized EA excitations are shown to exist.Comment: 10 pages, 5 figures; to appear in Phys. Rev.

An fMRI investigation of the relationship between future imagination and cognitive flexibility

While future imagination is largely considered to be a cognitive process grounded in default mode network activity, studies have shown that future imagination recruits regions in both default mode and frontoparietal control networks. In addition, it has recently been shown that the ability to imagine the future is associated with cognitive flexibility, and that tasks requiring cognitive flexibility result in increased coupling of the default mode network with frontoparietal control and salience networks. In the current study, we investigated the neural correlates underlying the association between cognitive flexibility and future imagination in two ways. First, we experimentally varied the degree of cognitive flexibility required during future imagination by manipulating the disparateness of episodic details contributing to imagined events. To this end, participants generated episodic details (persons, locations, objects) within three social spheres; during fMRI scanning they were presented with sets of three episodic details all taken from the same social sphere (Congruent condition) or different social spheres (Incongruent condition) and required to imagine a future event involving the three details. We predicted that, relative to the Congruent condition, future simulation in the Incongruent condition would be associated with increased activity in regions of the default mode, frontoparietal and salience networks. Second, we hypothesized that individual differences in cognitive flexibility, as measured by performance on the Alternate Uses Task, would correspond to individual differences in the brain regions recruited during future imagination. A task partial least squares (PLS) analysis showed that the Incongruent condition resulted in an increase in activity in regions in salience networks (e.g. the insula) but, contrary to our prediction, reduced activity in many regions of the default mode network (including the hippocampus). A subsequent functional connectivity (within-subject seed PLS) analysis showed that the insula exhibited increased coupling with default mode regions during the Incongruent condition. Finally, a behavioral PLS analysis showed that individual differences in cognitive flexibility were associated with differences in activity in a number of regions from frontoparietal, salience and default-mode networks during both future imagination conditions, further highlighting that the cognitive flexibility underlying future imagination is grounded in the complex interaction of regions in these networks

Change the IUCN protected area categories to reflect biodiversity outcomes

In 1872, United States President Ulysses Grant set aside 2.2 million acres of wilderness, primarily for recreational purposes, as the first formally recognized protected area (PA)—Yellowstone National Park. The concept took hold slowly over the next hundred years, and PAs are now recognized as essential to biodiversity conservation [1] and as irreplaceable tools for species and habitat management and recovery. Today, over 100,000 sites (11.5% of the Earth's land surface) are listed in the World Database on Protected Areas [2]. PAs have always been recognized as having broad roles, but it wasn't until the 1990s that the International Union for the Conservation of Nature (IUCN) included the role of conserving biodiversity in its definition: “An area of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources, and managed through legal or other effective means”..