273 research outputs found
The foraminiferal genera Pararotalia, Neorotalia, and Calcarina: taxonomic revision
Scanning electron microscopy of the architecture of Rotalina inermis Terquem, 1882, the type-species of the genus Pararotalia Le Calvez, 1949, and of Rotalia mexicana Nuttall, 1928, the type-species of the genus Neorotalia Bermudez, 1952, reveals that both taxa have in common: 1) an umbilical bowl closed by either a single or a compound umbilical plug; 2) an interiomarginal extraumbilical aperture, restricted by a toothplate that protrudes with a free edge into the aperture and forms an umbilical spiral canal; and 3) a septal flap and intraseptal interlocular spaces. Rotalia mexicana, however, also possesses an enveloping canal-system, similar to that found in the Calcarinidae. For this reason Neorotalia must be regarded as a valid distinct genus, not synonymous with Pararotalia, as proposed by some authors. Calcarina calcar d'Orbigny, 1839, variously placed by authors in Rotalia Lamarck, 1804, in Pararotalia Le Calvez, 1949, and lately again in Calcarina d'Orbigny, 1826, is shown to possess the same basic architecture as Neorotalia and is placed, consequently, into this latter genus. Irregular supplementary apertures occurring in N. calcar are not considered of generic value and neither are they regarded as indicating a relationship with Nautilus spengleri Gmelin, 1788, the type-species of Calcarina. The latter, although characterized by a complex enveloping canal-system, possesses primary multiple interioareal main apertures, surrounded by thick rims, as well as a small umbilical plate, but lacks a toothplate with a free edge. For comparison, Pararotalia spinigera (Le Calvez, 1949) and Neorotalia viennoti (Greig, 1935) were also studied. The subfamily Pararotaliinae Reiss, 1963, is emended to include the canal-system as a characteristic feature. A glossary of selected terms is appende
Existence of long-lived isotopes of a superheavy element in natural Au
Evidence for the existence of long-lived isotopes with atomic mass numbers
261 and 265 and abundance of (1-10)x10 relative to Au has been found in
a study of natural Au using an inductively coupled plasma - sector field mass
spectrometer. The measured masses fit the predictions made for the masses of
Rg and Rg (Z=111) and for some isotopes of nearby elements.
The possibility that these isotopes belong to the recently discovered class
of long-lived high spin super- and hyperdeformed isomeric states is discussed.Comment: 4 pages, 3 figures, 2 table
Heavy metal distribution in some French forest soils: evidence for atmospheric contamination
This study is one of very few dealing with the distribution and the origin of heavy metals in French soils from a
priori non-polluted forest areas. The abundance of heavy metals measured in these soils decreases as follows: Cr)
Zn)Pb)Ni)Cu)Co4Cd. Total concentrations of Pb, Cr and Ni in some soils exceed the European thresholds for non-polluted soils and even the French association of normalization critical values for sludge spreading. The lowest heavy metal contents are observed in acid soils while the highest concentrations are in the calcaric cambisol and in
the mollic andosol, which is rather scarce as compared with the other French forest soils. With the exception of the
podzol, Cr and Ni concentrations increase with depth in all soil profiles. The distribution pattern of Co, Cu, Zn
depends on the soil characteristics. In some acid soils, however, Cu and Zn decrease with depth. Pb and Cd are
accumulated in the upper soil horizons. Heavy metals accumulate in deep soil horizons in relation to important clay content in the dystric planosol and stagnic luvisol. The concentration of each heavy metal is always controlled by different parameters (soil pH, iron and aluminum oxide content, clay content, organic matter and cation exchange
capacity), which are heavy metal specific. This study highlights the metal-trapping character of andosol and calcaric soil, the weak heavy metal retention in acid soils, the leaching and trapping character in leached clayed soils, and the migration of heavy metals in the podzol. Pb and Cr concentrations indicate a significant enrichment in surface horizons from various soils in areas which receive significant acid atmospheric pollution. Particularly, the highest Pb content is observed in a soil located in the N-NE part of France. Lead isotope ratios measured in the cambic podzol and the calcaric cambisol, exhibit the importance of the anthropogenic sources and particularly the influence of global atmospheric inputs from leaded gasoline compared to regional and local industrial emissions. The anthropogenic Pb contribution is estimated to 83, 30 and 11%, respectively, for surface, intermediate and deep horizons of the cambic podzol located in the northern part of France, and to 68% in surface horizon of the calcaric cambisol located in the Alps
C. W. Smith i jego polscy korespondenci. C. W. Smith og hanspolske korrespondenter 1861-1879. Polska korespondencja z tłumaczeniem na duński
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