Low temperature fullerene encapsulation in single wall carbon nanotubes: synthesis of N@C60_{60}@SWCNT

High filling of single wall carbon nanotubes (SWCNT) with C$_{60}$ and C$_{70}$ fullerenes in solvent is reported at temperatures as low as 69 $^{o}$C. A 2 hour long refluxing in n-hexane of the mixture of the fullerene and SWCNT results in a high yield of C$_{60}$,C$_{70}$@SWCNT, fullerene peapod, material. The peapod filling is characterized by TEM, Raman and electron energy loss spectroscopy and X-ray scattering. We applied the method to synthesize the temperature sensitive (N@C$_{60}$:C$_{60}$)@SWCNT as proved by electron spin resonance spectroscopy. The solvent prepared peapod samples can be transformed to double walled nanotubes enabling a high yield and industrially scalable production of DWCNT

Low energy high angular resolution neutral atom detection by means of micro-shuttering techniques: the BepiColombo SERENA/ELENA sensor

The neutral sensor ELENA (Emitted Low-Energy Neutral Atoms) for the ESA cornerstone BepiColombo mission to Mercury (in the SERENA instrument package) is a new kind of low energetic neutral atoms instrument, mostly devoted to sputtering emission from planetary surfaces, from E ~20 eV up to E~5 keV, within 1-D (2x76 deg). ELENA is a Time-of-Flight (TOF) system, based on oscillating shutter (operated at frequencies up to a 100 kHz) and mechanical gratings: the incoming neutral particles directly impinge upon the entrance with a definite timing (START) and arrive to a STOP detector after a flight path. After a brief dissertation on the achievable scientific objectives, this paper describes the instrument, with the new design techniques approached for the neutral particles identification and the nano-techniques used for designing and manufacturing the nano-structure shuttering core of the ELENA sensor. The expected count-rates, based on the Hermean environment features, are shortly presented and discussed. Such design technologies could be fruitfully exported to different applications for planetary exploration.Comment: 11 page

Molecular Inventories and Chemical Evolution of Low-mass Protostellar Envelopes

This paper presents the first substantial study of the chemistry of the envelopes around a sample of 18 low-mass pre- and protostellar objects for which physical properties have previously been derived from radiative transfer modeling of their dust continuum emission. Single-dish line observations of 24 transitions of 9 molecular species (not counting isotopes) including HCO+, N2H+, CS, SO, SO2, HCN, HNC, HC3N and CN are reported. The line intensities are used to constrain the molecular abundances by comparison to Monte Carlo radiative transfer modeling of the line strengths. An empirical chemical network is constructed on the basis of correlations between the abundances of various species. For example, it is seen that the HCO+ and CO abundances are linearly correlated, both increasing with decreasing envelope mass. Species such as CS, SO and HCN show no trend with envelope mass. In particular no trend is seen between ``evolutionary stage'' of the objects and the abundances of the main sulfur- or nitrogen-containing species. Among the nitrogen-bearing species abundances of CN, HNC and HC3N are found to be closely correlated, which can be understood from considerations of the chemical network. The CS/SO abundance ratio is found to correlate with the abundances of CN and HC3N, which may reflect a dependence on the atomic carbon abundance. An anti-correlation is found between the deuteration of HCO+ and HCN, reflecting different temperature dependences for gas-phase deuteration mechanisms. The abundances are compared to other protostellar environments. In particular it is found that the abundances in the cold outer envelope of the previously studied class 0 protostar IRAS16293-2422 are in good agreement with the average abundances for the presented sample of class 0 objects.Comment: Accepted for publication in A&A. 29 pages, 23 figures. Abstract abridge

Electronic transport, structure, and energetics of endohedral Gd@C82 metallofullerenes

Electronic structure and transport properties of the fullerene C$_{82}$ and the metallofullerene Gd@C$_{82}$ are investigated with density functional theory and the Landauer-Buttiker formalism. The ground state structure of Gd@C$_{82}$ is found to have the Gd atom below the C-C bond on the C$_2$ molecular axis of C$_{82}$. Insertion of Gd into C$_{82}$ deforms the carbon chain in the vicinity of the Gd atoms. Significant overlap of the electron distribution is found between Gd and the C$_{82}$ cage, with the transferred Gd electron density localized mainly on the nearest carbon atoms. This charge localization reduces some of the conducting channels for the transport, causing a reduction in the conductivity of the Gd@C$_{82}$ species relative to the empty C$_{82}$ molecule. The electron transport across the metallofullerene is found to be insensitive to the spin state of the Gd atom.Comment: 13 pages, 7 figures, submitted Nano Let

Prediction of Anisotropic Single-Dirac-Cones in Bi1−x{}_{1-x}Sbx{}_{x} Thin Films

The electronic band structures of Bi${}_{1-x}$Sb${}_{x}$ thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi${}_{1-x}$Sb${}_{x}$ thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band-gap, which can be used in a general two-dimensional system that has a non-parabolic dispersion relation as in a Bi${}_{1-x}$Sb${}_{x}$ thin film system

Rapid enhancer remodeling and transcription factor repurposing enable high magnitude gene induction upon acute activation of NK cells

During development, innate lymphocytes acquire defined sets of primed enhancers facilitating the rapid immune response. In this issue of Immunity, Sciumè et al. delineate the epigenetic changes occurring during acute NK cell activation, revealing the formation of de novo enhancers and repurposing of both lineage-determining and signal-regulated transcription factors

Electro-Fluidic Shuttle Memory Device: Classical Molecular Dynamics Study

We investigated the internal dynamics of several electro-fluid shuttle memory elements, consisting of several media encapsulated in C640 nanocapsule. The systems proposed were (i) bucky shuttle memory devices (C36+ @C420 and C60+ @C420), (ii) encapsulated-ions shuttle memory devices ((13+)@C420, (3+ -C60-2+ )@C640 and (5+ -C60)@C640) and (iii) endo-fullerenes shuttle memory devices ((K+ @C60- F-@C60)@C640). Energetics and operating responses of several electro-fluidic shuttle memory devices, such as transitions between the two states of the C640 capsule, were examined by classical molecular dynamics simulations of the shuttle media in the C640 capsule under the external force fields. The operating force fields for the stable operations of the shuttle memory device were investigated