21 research outputs found
Response of grazing snails to phosphorus enrichment of modern stromatolitic microbial communities
Feasibility studies for the measurement of time-like proton electromagnetic form factors from pÂŻ pâ ÎŒ+ÎŒ- at P ÂŻ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the pÂŻ pâ ÎŒ+ÎŒ- reaction at P ÂŻ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ÂŻ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is pÂŻ pâ Ï+Ï-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
Comment on âAn enigmatic, possibly chemosymbiotic, hexactinellid sponge from the early Cambrian of South Chinaâ by Joseph P. Botting, Lucy A. Muir, Xiang-Feng Li, and Jin-Pai Lin
A probable oligochaete from an Early Triassic Lagerstatte of the southern Cis-Urals and its evolutionary implications
Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, are extremely rare fossils.
The palaeontological record of these worms is restricted to some cocoons, presumable trace fossils and a few body fossils
the most convincing of which are discovered in Mesozoic and Cenozoic strata. The Olenekian (Lower Triassic) siliciclastic
lacustrine Petropavlovka LagerstÀtte of the southern Cis-Urals yields a number of extraordinary freshwater fossils including
an annelid. The segmented body with a secondary annulation of this fossil, a subtriangular prostomium, a relatively thick
layered body wall and, possibly, the presence of a genital region point to its oligochaete affinities. Other fossil worms which
have been ascribed to clitellates are reviewed and, with a tentative exception of two Pennsylvanian finds, affinities of any
pre-Mesozoic forms to clitellate annelids are rejected. The new fossil worm allows tracing of a persuasive oligochaete
record to the lowermost Mesozoic and confirms a plausibility of the origin of this annelid group in freshwater conditions
New finds of skeletal fossils in the terminal Neoproterozoic of the Siberian Platform and Spain
A current paradigm accepts the presence of weakly biomineralized animals only, barely above a low metazoan grade of organization in the terminal Neoproterozoic (Ediacaran), and a later, early Cambrian burst of well skeletonized animals. Here we report new assemblages of primarily calcareous shelly fossils from upper Ediacaran (553â542 Ma) carbonates of Spain and Russia (Siberian Platform). The problematic organism Cloudina is found in the Yudoma Group of the southeastern Siberian Platform and different skeletal taxa have been discovered in the terminal Neoproterozoic of several provinces of Spain. New data on the morphology and microstructure of Ediacaran skeletal fossils Cloudina and Namacalathus indicate that the Neoproterozoic skeletal organisms were already reasonably advanced. In total, at least 15 skeletal metazoan genera are recorded worldwide within this interval. This number is comparable with that known for the basal early Cambrian. These data reveal that the terminal Neoproterozoic skeletal bloom was a real precursor of the Cambrian radiation. Cloudina, the oldest animal with a mineralised skeleton on the Siberian Platform, characterises the uppermost Ediacaran strata of the UstââYudoma Formation. While in Siberia Cloudina coâoccurs with small skeletal fossils of Cambrian aspect, in Spain Cloudinaâbearing carbonates and other Ediacaran skeletal fossils alternate with strata containing rich terminal Neoproterozoic trace fossil assemblages. These finds treated together provide a possibility to correlate transitional Neoproterozoicâ lower Cambrian strata around the world. Such a correlation concurs with available isotope and radiometric data and indicates that typical Ediacaran shelly fossils have not crossed the PrecambrianâCambrian boundary
Organic chemistry. History and mutual relations of universities of Russia
The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now. © 2017, Pleiades Publishing, Ltd
Organic chemistry. History and mutual relations of universities of Russia
The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now. © 2017, Pleiades Publishing, Ltd
Sponge spicule assemblages from the Cambrian (Series 2?3) of North Greenland (Laurentia) : systematics and biogeography
Isolated microscopic spicules from disarticulated scleritomes demonstrate the presence of a diverse sponge fauna otherwise not evident from the macrofossil record in carbonate successions deposited during the un-named Cambrian Series 2 and Cambrian Series 3 (Miaolingian) in North Greenland. Most of the spicule morphotypes are not recognised from faunas of articulated sponges known from contemporaneous siliciclastic strata elsewhere. Assemblages are described in terms of four Cambrian stages and contain numerous spicule morphotypes not previously recorded from Laurentia. Many of the spicules can be correlated worldwide, however, extending current knowledge of the biogeographic distribution of sponge spicule-based taxa in the Cambrian. In particular, similar Cambrian Stage 4 (Series 2) and Miaolingian assemblages (Wuliuan, Drumian and Guzhangian stages) faunas are recorded from tropical palaeolatitudes in Australia, South China, Siberia and Laurentia, although this may in part reflect a methodology focused on the preparation of the carbonate samples that dominate these successions. New spicule-based taxa: Eiffelia floriformis n. sp., Australispongia? inuak n. sp., Celtispongia dorte n. gen. n. sp., Sanningasoqia borealis n. gen. n. sp., Speciosuspongia inughuitorum n. sp., Sulukispicula gelidae n. gen. n. sp