Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory

Here, we review the historical development, current status, and prospects of Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only theory.Comment: 15 page

Measurements of prompt charm production cross-sections in pp collisions at s=5 \sqrt{s}=5 TeV

See paper for full list of authors - All figures and tables, along with any supplementary material and additional information, are available at this https URL - Submitted to JHEPInternational audienceProduction cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5TeV. The data sample corresponds to an integrated luminosity of 8.60±0.33pb−1 collected by the LHCb experiment. The production cross-sections of D0, D+, D+s, and D∗+ mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y. They cover the rapidity range 2.0<y<4.5 and transverse momentum ranges 0<pT<10GeV/c for D0 and D+ and 1<pT<10GeV/c for D+s and D∗+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1<pT<8GeV/c are determined to beσ(pp→D0X)=1190±3±64μbσ(pp→D+X)=456±3±34μbσ(pp→D+sX)=195±4±19μbσ(pp→D∗+X)=467±6±40μbwhere the uncertainties are statistical and systematic, respectively

Hummingbird diversity, food niche characters, and assemblage composition along a latitudinal precipitation gradient in the Bolivian lowlands

As for many other taxa, hummingbird diversity declines away from the equator, but the causes for this decline are still disputed and might involve, among others, climatic factors or the availability of food resources. Because hummingbirds are one of the classical examples for plant–animal coevolution, it has been proposed that the diversity of hummingbird assemblages might depend on the diversity of food plants available. We tested this hypothesis by studying the hummingbird assemblages and their food plants for 1 year at six sites along a 660-km-long transect in Bolivian lowland forests extending from the southernmost Amazonian rain forests to dry Chaco forests. Hummingbird diversity was higher in the northern three sites as compared to the southern ones, with an abrupt decline in species numbers and a corresponding change in taxonomic composition at the boundary from evergreen to drought deciduous forests. Hummingbird diversity and abundance were only weakly correlated to climatic factors or to the diversity of humming-visited flowers, but strongly to the seasonal abundance of flowers. The overlap in nectar diet between hummingbird species depended on the number of plant species: when numerous species were available, the hummingbirds segregated by feeding preferences, but when few flowers were available, all hummingbirds fed on the same plants. We conclude that the local diversity of hummingbird species is not primarily determined by the diversity of food plants, but rather by the abundance of flowers available at any given point in time