58 research outputs found
Ultramafic vegetation and soils in the circumboreal region of the Northern Hemisphere
The paper summarizes literature on climate, soil chemistry, vegetation and metal accumulation by plants found on ultramafic substrata in the circumboreal zone (sensu Takhtajan, Floristic regions of the world, 1986) of the Northern Hemisphere. We present a list of 50 endemic species and 18 ecotypes obligate to ultramafic soils from the circumboreal region of Holarctic, as well as 30 and 2 species of Ni and Zn hyperaccumulators, respectively. The number of both endemics and hyperaccumulators are markedly lower compared to that of the Mediterranean and tropical regions. The diversity of plant communities on ultramafics soils of the circumboral region is also described. The underlying causes for the differences of ultramafic flora between arctic, cold, cool temperate and Mediterranean and tropical regions are also discussed. © 2018, The Ecological Society of Japan
Measurement of angular correlations of jets at root s=1.96 TeV and determination of the strong coupling at high momentum transfers
We present a measurement of the average value of a new observable at hadron colliders that is sensitive
to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton
distribution functions. The observable measures the angular correlations of jets and is defined as the
number of neighboring jets above a given transverse momentum threshold which accompany a given jet
within a given distance �R in the plane of rapidity and azimuthal angle. The ensemble average over all
jets in an inclusive jet sample is measured and the results are presented as a function of transverse
momentum of the inclusive jets, in different regions of �R and for different transverse momentum
requirements for the neighboring jets. The measurement is based on a data set corresponding to an
integrated luminosity of 0.7 fb−1 collected with the D0 detector at the Fermilab Tevatron Collider in p¯p
collisions at
√
s = 1.96 TeV. The results are well described by a perturbative QCD calculation in next-toleading
order in the strong coupling constant, corrected for non-perturbative effects. From these results,
we extract the strong coupling and test the QCD predictions for its running over a range of momentum
transfers of 50–400 GeV
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