1,128 research outputs found
Spin-transfer mechanism of ferromagnetism in polymerized fullerenes: calculations
A mechanism of the high temperature ferromagnetism in polymerized fullerenes
is suggested. It is assumed that some of the C molecules in the crystal
become magnetically active due to spin and charge transfer from the
paramagnetic impurities (atoms or groups), such as hydrogen, fluorine, hydroxyl
group OH, amino group NH, or methyl group CH, dispersed in the
fullerene matrix. The exchange interaction between the spins localized on the
magnetically active fullerenes is evaluated using \textit{ab initio}
calculations. The nearest neighbour and next nearest neighbour exchange
interaction is found to be in the range eV, that is, high enough
to account for the room temperature ferromagnetism.Comment: typos corrected, 8 pages, 3 figures, LaTe
Observation of Magnetic Edge State and Dangling Bond State on Nanographene in Activated Carbon Fibers
The electronic structure of nanographene in pristine and fluorinated
activated carbon fibers (ACFs) have been investigated with near-edge x-ray
absorption fine structure (NEXAFS) and compared with magnetic properties we
reported on previously. In pristine ACFs in which magnetic properties are
governed by non-bonding edge states of the \pi-electron, a pre-peak assigned to
the edge state was observed below the conduction electron {\pi}* peak close to
the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak,
which was assigned to the \sigma-dangling bond state, was observed between the
pre-peak of the edge state and the {\pi}* peak in the NEXAFS profile. The
intensities of the extra peak correlate closely with the spin concentration
created upon fluorination. The combination of the NEXAFS and magnetic
measurement results confirms the coexistence of the magnetic edge states of
\pi-electrons and dangling bond states of \sigma-electrons on fluorinated
nanographene sheets.Comment: 4 figures, to appear in Phys. Rev.
Detecting bivariate outliers on the basis of normalizing transformations for non-Gaussian data
The statistical technique for detecting
outliers in bivariate non-Gaussian data on the basis of
normalizing transformations, prediction ellipse and a
test statistic (TS) for the Mahalanobis squared
distance (MSD), which has an approximate F
distribution, is proposed. Application of the technique
is considered for detecting outliers in two bivariate
non-Gaussian data sets: the first, actual effort (hours)
and size (adjusted function points) from 145
maintenance and development projects, the second,
effort (hours) and mass (tonnes) of designed the
section of the ship from 188 designs of sections
Fingerprints of Spin-Orbital Physics in Crystalline O
The alkali hyperoxide KO is a molecular analog of strongly-correlated
systems, comprising of orbitally degenerate magnetic O ions. Using
first-principles electronic structure calculations, we set up an effective
spin-orbital model for the low-energy \textit{molecular} orbitals and argue
that many anomalous properties of KO replicate the status of its orbital
system in various temperature regimes.Comment: 4 pages, 2 figures, 1 tabl
Detecting bivariate outliers on the basis of normalizing transformations for non-Gaussian data
The statistical technique for detecting
outliers in bivariate non-Gaussian data on the basis of
normalizing transformations, prediction ellipse and a
test statistic (TS) for the Mahalanobis squared
distance (MSD), which has an approximate F
distribution, is proposed. Application of the technique
is considered for detecting outliers in two bivariate
non-Gaussian data sets: the first, actual effort (hours)
and size (adjusted function points) from 145
maintenance and development projects, the second,
effort (hours) and mass (tonnes) of designed the
section of the ship from 188 designs of sections
Improved genome editing in human cell lines using the CRISPR method
The Cas9/CRISPR system has become a popular choice for genome editing. In this system, binding of a single guide (sg) RNA to a cognate genomic sequence enables the Cas9 nuclease to induce a double-strand break at that locus. This break is next repaired by an error-prone mechanism, leading to mutation and gene disruption. In this study we describe a range of refinements of the method, including stable cell lines expressing Cas9, and a PCR based protocol for the generation of the sgRNA. We also describe a simple methodology that allows both elimination of Cas9 from cells after gene disruption and re-introduction of the disrupted gene. This advance enables easy assessment of the off target effects associated with gene disruption, as well as phenotype-based structure-function analysis. In our study, we used the Fan1 DNA repair gene as control in these experiments. Cas9/CRISPR-mediated Fan1 disruption occurred at frequencies of around 29%, and resulted in the anticipated spectrum of genotoxin hypersensitivity, which was rescued by re-introduction of Fan1
Kramers-Kronig constrained variational analysis of optical spectra
A universal method of extraction of the complex dielectric function
from
experimentally accessible optical quantities is developed. The central idea is
that is parameterized independently at each node of a
properly chosen anchor frequency mesh, while is
dynamically coupled to by the Kramers-Kronig (KK)
transformation. This approach can be regarded as a limiting case of the
multi-oscillator fitting of spectra, when the number of oscillators is of the
order of the number of experimental points. In the case of the normal-incidence
reflectivity from a semi-infinite isotropic sample the new method gives
essentially the same result as the conventional KK transformation of
reflectivity. In contrast to the conventional approaches, the proposed
technique is applicable, without readaptation, to virtually all types of
linear-response optical measurements, or arbitrary combinations of
measurements, such as reflectivity, transmission, ellipsometry {\it etc.}, done
on different types of samples, including thin films and anisotropic crystals.Comment: 10 pages, 7 figure
Magnetic properties of carbon phases synthesized using high pressure-high temperature treatment
Two sets of samples were synthesized at 3.5 GPa near the point of C60 cage
collapse at different annealing times. A clear structural transformation from
mixture of C60 polymeric phases to graphite-like hard carbon phase was
confirmed by X-ray diffraction and Raman spectroscopy. Magnetic force
microscopy and superconducting quantum interference device were used to
characterize the magnetic properties of the synthesized samples. We found that
the sample preparation conditions used in this study are not suitable to
produce bulk magnetic carbon.Comment: 26 pages, 7 figure
Understanding Human and Ecosystem Dynamics in the Kola Arctic : A Participatory Integrated Study
The Lake Imandra watershed is located in one of the most developed regions in the Arctic - the Kola Peninsula of Russia. Approximately 300 000 people live on the roughly 27 000 km² watershed, making it one of the most densely populated areas of the Arctic. Most of the people are involved in large-scale mineral extraction and processing and the infrastructure needed to support this industry. This paper reports the results of a pilot project staged for the Lake Imandra watershed that has put human dynamics within the framework of ecosystem change to integrate available information and formulate conceptual models of likely future scenarios. The observation period is one of both rapid economic growth and human expansion, with an overall economic decline in the past decade. We are applying the Participatory Integrated Assessment (PIA) approach to integrate information, identify information gaps, generate likely future scenarios, and link scientific findings to the decision-making process. We found an increasingly vulnerable human population in varying states of awareness about their local environment and fully cognizant of their economic troubles, with many determined to attempt maintenance of relatively high population densities in the near future even as many residents of northern Russia migrate south. A series of workshops have involved the citizens and local decision makers in an attempt to tap their knowledge of the region and to increase their awareness about the linkages between the socioeconomic and ecological components.Le bassin hydrographique du lac Imandra est situé dans l'une des régions les plus développées de l'Arctique, soit la presqu'île de Kola, en Russie. Près de 300 000 personnes vivent dans la zone du bassin qui couvre environ 27 000 km², ce qui en fait l'une des régions les plus peuplées de l'Arctique. La plupart des habitants travaillent dans l'extraction et le traitement miniers à grande échelle ainsi que dans l'infrastructure qui soutient cette industrie. Le présent article rapporte les résultats d'un projet pilote mis sur pied pour le bassin du lac Imandra, projet qui a placé la dynamique humaine dans le cadre du changement des écosystèmes, afin d'intégrer l'information disponible et de formuler des modèles conceptuels de scénarios probables dans l'avenir. La période d'observation en est une à la fois de croissance économique et d'expansion démographique rapides, suivie d'un déclin général au cours de la dernière décennie. On a recours à la méthode d'évaluation participative intégrée (EPI) pour intégrer l'information, y dégager des lacunes, générer des scénarios probables dans l'avenir et établir un lien entre résultats de la recherche et processus décisionnel. On a trouvé qu'il y avait une population humaine de plus en plus vulnérable qui était sensibilisée à divers degrés aux problèmes locaux de l'environnement et pleinement consciente des difficultés économiques, population dont une bonne part était fermement décidée à tenter de maintenir à brève échéance des densités de population relativement élevées, alors même que les résidents du nord de la Russie migrent en grand nombre vers le Sud. On a tenu une série d'ateliers avec citoyens et décideurs locaux pour chercher à capter leurs connaissances de la région et à accroître leur sensibilisation aux liens existant entre les composantes socio-économiques et écologiques
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