Transformation of amorphous carbon clusters to fullerenes

Transformation of amorphous carbon clusters into fullerenes under high temperature is studied using molecular dynamics simulations at microsecond times. Based on the analysis of both structure and energy of the system, it is found that fullerene formation occurs in two stages. Firstly, fast transformation of the initial amorphous structure into a hollow sp$^2$ shell with a few chains attached occurs with a considerable decrease of the potential energy and the number of atoms belonging to chains and to the amorphous domain. Then, insertion of remaining carbon chains into the sp$^2$ network takes place at the same time with the fullerene shell formation. Two types of defects remaining after the formation of the fullerene shell are revealed: 7-membered rings and single one-coordinated atoms. One of the fullerene structures obtained contains no defects at all, which demonstrates that defect-free carbon cages can be occasionally formed from amorphous precursors directly without defect healing. No structural changes are observed after the fullerene formation, suggesting that defect healing is a slow process in comparison with the fullerene shell formation. The schemes of the revealed reactions of chain atoms insertion into the fullerene shell just before its completion are presented. The results of the performed simulations are summarized within the paradigm of fullerene formation due to selforganization of the carbon system.Comment: 35 pages, 9 figure

Formation of nickel-carbon heterofullerenes under electron irradiation

arXiv.-- et al.A way to produce new metal-carbon nanoobjects by transformation of a graphene flake with an attached transition metal cluster under electron irradiation is proposed. The transformation process is investigated by molecular dynamics simulations by the example of a graphene flake with a nickel cluster. The parameters of the nickel-carbon potential (I. V. Lebedeva et al., J. Phys. Chem. C, 2012, 116, 6572) are modified to improve the description of the balance between the fullerene elastic energy and graphene edge energies in this process. The metal-carbon nanoobjects formed are found to range from heterofullerenes with a metal patch to particles consisting of closed fullerene and metal clusters linked by chemical bonds. The atomic-scale transformation mechanism is revealed by the local structure analysis. The average time of formation of nanoobjects and their lifetime under electron irradiation are estimated for the experimental conditions of high-resolution transmission electron microscopy (HRTEM). The sequence of images of nanostructure evolution with time during its observation by HRTEM is also modelled. Furthermore, the possibility of batch production of studied metal-carbon nanoobjects and solids based on these nanoobjects is discussed.AS, IL, AK and AP acknowledges Russian Foundation of Basic Research (14-02-00739-a). AP acknowledges Samsung Global Research Outreach Program. IL acknowledges support from the Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (Grant Agreement PIIF-GA-2012-326435 RespSpatDisp), Grupos Consolidados del Gobierno Vasco (IT-578-13) and the computational time on the Supercomputing Center of Lomonosov Moscow State University and the Multipurpose Computing Complex NRC “Kurchatov Institute.” EB acknowledges EPSRC Career Acceleration Fellowship, New Directions for EPSRC Research Leaders Award (EP/G005060), and ERC Starting Grant for financial support.Peer Reviewe

New Bryokhutuliinia species (bryophyta) with sporophytes from the upper jurassic of Transbaikalia

A new species of the moss genus Bryokhutuliinia, B. crassimarginata is described from the Upper Jurassic deposits from the Olov, Transbaikal Area of South Siberia. Its excellent preservation demonstra- tes that the leaves were not only complanate, but truly distichous. In addition to anatomically pre- served gametophytes, sporophytes on short lateral branches were found, although carbonized and not exhibiting structural details. Possible relationships with pleurocarpous mosses and with Fissidentaceae are discussedyesBelgorod State National Research Universit

Study (301)-(000) D2O band in 10200 - 10450 cm-1 spectral region

Measurements of D2O absorption spectra in the visible spectral region near 0.98 μm are performed using FT-spectrometer IFS-125M and Light-emitting diode (LED) as source of radiation. Water vapor spectrum has been obtained by averaging over 17136 scans recorded at 24 m optical path length, temperature 24 С and pressure of sample 27 mBar. Due to strong emission of LED source it was possible to achieve signal-to-noise ratio about 104 and to record weak lines with intensities of 6 10-27 cm/molecule. Comparisons with results of early works are made. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

The rise of feathered dinosaurs:Kulindadromeus zabaikalicus, the oldest dinosaur with ‘feather-like’ structures

Diverse epidermal appendages including grouped filaments closely resembling primitive feathers in non-avian theropods, are associated with skeletal elements in the primitive ornithischian dinosaur Kulindadromeus zabaikalicus from the Kulinda locality in south-eastern Siberia. This discovery suggests that ‘‘feather-like’’ structures did not evolve exclusively in theropod dinosaurs, but were instead potentially widespread in the whole dinosaur clade. The dating of the Kulinda locality is therefore particularly important for reconstructing the evolution of ‘‘feather-like’’ structures in dinosaurs within a chronostratigraphic framework. Here we present the first dating of the Kulinda locality, combining U-Pb analyses (LA-ICP-MS) on detrital zircons and monazites from sedimentary rocks of volcaniclastic origin and palynological observations. Concordia ages constrain the maximum age of the volcaniclastic deposits at 172.8 ± 1.6 Ma, corresponding to the Aalenian (Middle Jurassic). The palynological assemblage includes taxa that are correlated to Bathonian palynozones from western Siberia, and therefore constrains the minimum age of the deposits. The new U-Pb ages, together with the palynological data, provide evidence of a Bathonian age—between 168.3 ± 1.3 Ma and 166.1 ± 1.2 Ma—for Kulindadromeus. This is older than the previous Late Jurassic to Early Cretaceous ages tentatively based on local stratigraphic correlations. A Bathonian age is highly consistent with the phylogenetic position of Kulindadromeus at the base of the neornithischian clade and suggests that cerapodan dinosaurs originated in Asia during the Middle Jurassic, from a common ancestor that closely looked like Kulindadromeus. Our results consequently show that Kulindadromeus is the oldest known dinosaur with ‘‘feather-like’’ structures discovered so far.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

New Bryokhutuliinia species (bryophyta) with sporophytes from the upper jurassic of Transbaikalia

yesA new species of the moss genus Bryokhutuliinia, B. crassimarginata is described from the Upper Jurassic deposits from the Olov, Transbaikal Area of South Siberia. Its excellent preservation demonstra- tes that the leaves were not only complanate, but truly distichous. In addition to anatomically pre- served gametophytes, sporophytes on short lateral branches were found, although carbonized and not exhibiting structural details. Possible relationships with pleurocarpous mosses and with Fissidentaceae are discussedBelgorod State National Research Universit

Transformation of amorphous carbon clusters to fullerenes

Transformation of amorphous carbon clusters into fullerenes under high temperature is studied using molecular dynamics simulations at microsecond times. On the basis of the analysis of both the structure and energy of the system, it is found that fullerene formation occurs in two stages. First, fast transformation of the initial amorphous structure into a hollow sp shell with a few chains attached occurs with a considerable decrease of the potential energy and the number of atoms belonging to chains and to the amorphous domain. Then insertion of the remaining carbon chains into the sp network takes place at the same time as the fullerene shell formation. Two types of defects remaining after the formation of the fullerene shell are revealed: seven-membered rings and single one-coordinated atoms. One of the fullerene structures obtained contains no defects at all, which demonstrates that defect-free carbon cages can be occasionally formed from amorphous precursors directly without defect healing. No structural changes are observed after the fullerene formation, suggesting that defect healing is a slow process in comparison with the fullerene shell formation. The schemes of the revealed reactions of chain atom insertion into the fullerene shell just before its completion are presented. The results of the performed simulations are summarized within the paradigm of fullerene formation due to self-organization of the carbon system.This research was supported by the Russian Foundation of Basic Research (Grant 14-02-00739-a). I.V.L. acknowledges Grupos Consolidados del Gobierno Vasco (Grant IT-578-13) and EU-H2020 Project “MOSTOPHOS” (No. 646259).Peer Reviewe