Satellite channel sharing and its implications for computer networks

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Interplay of Soundcone and Supersonic Propagation in Lattice Models with Power Law Interactions

We study the spreading of correlations and other physical quantities in quantum lattice models with interactions or hopping decaying like $r^{-\alpha}$ with the distance $r$. Our focus is on exponents $\alpha$ between 0 and 6, where the interplay of long- and short-range features gives rise to a complex phenomenology and interesting physical effects, and which is also the relevant range for experimental realizations with cold atoms, ions, or molecules. We present analytical and numerical results, providing a comprehensive picture of spatio-temporal propagation. Lieb-Robinson-type bounds are extended to strongly long-range interactions where $\alpha$ is smaller than the lattice dimension, and we report particularly sharp bounds that are capable of reproducing regimes with soundcone as well as supersonic dynamics. Complementary lower bounds prove that faster-than-soundcone propagation occurs for $\alpha<2$ in any spatial dimension, although cone-like features are shown to also occur in that regime. Our results provide guidance for optimizing experimental efforts to harness long-range interactions in a variety of quantum information and signaling tasks.Comment: 20 pages, 8 figure

The Human Virome in Children and its Relationship to Febrile Illness

This study investigates the relationship of viruses to febrile illness in children. Subjects are normal children 2-36 months of age with fever along with normal children of the same age without fever, plus immunocompromised children with fever along with immunocompromised children without fever. Specimens obtained include blood, nasopharyngeal secretions, and feces. Specimens are analyzed using a panel of virus-specific PCR assays and also by high throughput sequencing using 454 and Illumina platforms

Structure of the species-energy relationship

The relationship between energy availability and species richness (the species-energy relationship) is one of the best documented macroecological phenomena. However, the structure of species distribution along the gradient, the proximate driver of the relationship, is poorly known. Here, using data on the distribution of birds in southern Africa, for which species richness increases linearly with energy availability, we provide an explicit determination of this structure. We show that most species exhibit increasing occupancy towards more productive regions (occurring in more grid cells within a productivity class). However, average reporting rates per species within occupied grid cells, a correlate of local density, do not show a similar increase. The mean range of used energy levels and the mean geographical range size of species in southern Africa decreases along the energy gradient, as most species are present at high productivity levels but only some can extend their ranges towards lower levels. Species turnover among grid cells consequently decreases towards high energy levels. In summary, these patterns support the hypothesis that higher productivity leads to more species by increasing the probability of occurrence of resources that enable the persistence of viable populations, without necessarily affecting local population densities

Geographic trends in range sizes explain patterns in bird responses to urbanization in Europe

The probability of occurrence of bird species in towns/cities increases with their range sizes, and Rapoport’s&nbsp;rule states that range sizes increase with latitude. To test the hypothesis that the increasing number of bird&nbsp;species persisting in cities at higher latitudes of Europe is linked to their larger range sizes, we compiled data on&nbsp;bird communities of: a) 41 urban bird atlases; b) 37 city core zones from published sources; c) regions of nine&nbsp;grid cells of the EBCC Atlas of European Breeding Birds around each city. We tested whether the proportion of&nbsp;species from particular regional bird assemblages entering cities (i.e., proportional richness) was related to the&nbsp;geographical &nbsp;position, mean range size of regional avifaunas, proportion of vegetated areas and city habitat&nbsp;heterogeneity. The mean range sizes of the observed and randomly selected urban avifaunas were contrasted.&nbsp;The proportional richness of urban avifaunas was positively related to the geographic position and mean range&nbsp;size of birds in regional assemblages. The evidence favoured range sizes if considering the European range sizes&nbsp;or latitudinal extents, but was limited for global range sizes. Randomizations tended to show larger range sizes&nbsp;for the real avifaunas than in the randomly selected ones. For urban core zones, the results were less clear-cut&nbsp;with some evidence only in favour of the European range sizes. No role of vegetation or habitat heterogeneity&nbsp;was found. In conclusion, while vegetation availability or heterogeneity did not show any effects, spatial position&nbsp;and range sizes of birds in regional assemblages seemed to influence the proportional richness of cities and their&nbsp;core zones. Factors correlated with spatial position (e.g., climate) might increase the attractivity of particular cities to birds. However, the effects of range sizes indicated that urbanization possibly has more negative impacts&nbsp;on the avifauna in the regions occupied by less widespread species

Protocols and pitfalls in obtaining fatty acid-binding proteins for biophysical studies of ligand-protein and protein-protein interactions

Adipocyte fatty acid-binding protein (AFABP: FABP4) is a member of the intracellular lipid-binding protein family that is thought to target long-chain fatty acids to nuclear receptors such as peroxisome proliferatoractivated receptor gamma (PPARγ), which in turn plays roles in insulin resistance and obesity. A molecular understanding of AFABP function requires robust isolation of the protein in liganded and free forms as well as characterization of its oligomerization state(s) under physiological conditions. We report development of a protocol to optimize the production of members of this protein family in pure form, including removal of their bound lipids by mixing with hydrophobically functionalized hydroxypropyl dextran beads and validation by two-dimensional NMR spectroscopy. The formation of self-associated or covalently bonded protein dimers was evaluated critically using gel filtration chromatography, revealing conditions that promote or prevent formation of disulfide-linked homodimers. The resulting scheme provides a solid foundation for future investigations of AFABP interactions with key ligand and protein partners involved in lipid metabolism

Three-dimensional space utilisation in a marine predator

Diving seabirds should evolve a variety of foraging characteristics which enable them to minimize energy expenditure and to maximize net energy gain while searching for prey underwater. In order to assess the related ecological adaptations in a marine predator, we studied the at-sea distribution and the diving behaviour of 23 cormorants Phalacrocorax carbo (Linnaeus) breeding at the Chausey Islands (France) using VHF-telemetry and data loggers recording hydrostatic pressure. Birds foraged within an area of approximately 1131 km2 situated north-east of the breeding colony. This zone represents only 25% of the maximal potentially available area that the birds may utilize considering their maximum foraging range of 35 km. Individual birds remained within restricted individual foraging areas (on average 18 and 10% of the total utilized area in 1994 and 1995, respectively) throughout the study period. Moreover, the cormorants studied conducted an average of 42 dives per foraging trip, lasting for an average of 40 s (maximum 152 s), and reached an average maximum dive depth of 6.1 m (maximum 32 m) with median descent and ascent angles calculated to be 18.7° and 20.3°, respectively. Overall, 64% of all dives were U-shaped dives and 36% V-shaped dives. We use these results to demonstrate how both specialization and opportunism may support the remarkably high foraging efficiency of this marine predator