18,732 research outputs found
Critical current and topology of the supercooled vortex state in NbSe2
We study the behavior of the critical current, Ic(H,T), of pure and Fe doped
NbSe2 crystals in the denominated disordered vortex region, limited by the
critical field Hc2(T) and the field Hp(T) at which the peak effect in Ic(H,T)
is detected. The critical current follows an individual pinning response as
demonstrated by its field independent universal function of the superfluid
density. Transport measurements combined with Bitter decorations show no
evidence of the existence of an amorphous phase in the high temperature region.Comment: 7 pages, figures included. Submitted to Phys. Rev.
A phytosociological survey of the boreal forest (Vaccinio-Piceetea) in North America
A survey of syntaxa of vegetation of North American boreal forests (class Vaccinio-Piceetea) is presented. This
phytosociological survey, carried out combining the Braun-Blanquet method with numerical syntaxonomical analyses
(cluster and correspondence analysis), describes the associations of the North American boreal forests, which
have several species, varieties or vicariant species in common with their Eurasian counterparts, and can be placed
in the class Vaccinio-Piceetea. By means of tabular and multivariate analyses, 2084 North American relevés were
compared with 3273 relevés from European, Japanese and Korean boreal forest, to describe and typify 4 orders, 10
alliances and 37 associations. Diagnostic tables, ordination, clustering, and climatic, edaphic and biogeographical data were used to show floristic affinities among these syntaxa and interpret their distribution areas. Syntaxa were briefly characterized by their floristic composition, physiognomy, succession, zonation, and biogeographical distribution
Surface-induced layer formation in polyelectrolytes
We analyze, by means of an RPA calculation, the conditions under which a
mixture of oppositely charged polyelectrolytes can micro-segregate in the
neighborhood of a charged surface creating a layered structure. A number of
stable layers can be formed if the surface is sufficiently strongly charged
even at temperatures at which the bulk of the mixture is homogeneous.Comment: 6 pages, 3 figures, revtex, epsf, psfi
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