On Infravacua and the Localisation of Sectors

A certain class of superselection sectors of the free massless scalar field in 3 space dimensions is considered. It is shown that these sectors, which cannot be localised with respect to the vacuum, acquire a much better localisation, namely in spacelike cones, when viewed in front of suitable ``infravacuum'' backgrounds. These background states coincide, essentially, with a class of states introduced by Kraus, Polley and Reents as models for clouds of infrared radiation.Comment: LaTeX, 18 pages, minor corrections in order to conform with published versio

On Infravacua and Superselection Theory

In the DHR theory of superselection sectors, one usually considers states which are local excitations of some vacuum state. Here, we extend this analysis to local excitations of a class of "infravacuum" states appearing in models with massless particles. We show that the corresponding superselection structure, the statistics of superselection sectors and the energy-momentum spectrum are the same as with respect to the vacuum state. (The latter result is obtained with a novel method of expressing the shape of the spectrum in terms of properties of local charge transfer cocycles.) These findings provide evidence to the effect that infravacua are a natural starting point for the analysis of the superselection structure in theories with long-range forces.Comment: LaTeX, 18 pages, spelling errors correcte

Spacelike localization of long-range fields in a model of asymptotic electrodynamics

A previously proposed algebra of asymptotic fields in quantum electrodynamics is formulated as a net of algebras localized in regions which in general have unbounded spacelike extension. Electromagnetic fields may be localized in `symmetrical spacelike cones', but there are strong indications this is not possible in the present model for charged fields, which have tails extending in all space directions. Nevertheless, products of appropriately `dressed' fermion fields (with compensating charges) yield bi-localized observables.Comment: 29 pages, accepted for publication in Annales Henri Poincar\'

Combining carbon nanotubes and chitosan for the vectorization of methotrexate to lung cancer cells

A hybrid system composed of multi-walled carbon nanotubes coated with chitosan was proposed as a pH-responsive carrier for the vectorization of methotrexate to lung cancer. The effective coating of the carbon nanostructure by chitosan, quantified (20% by weight) by thermogravimetric analysis, was assessed by combined scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy (N1s signal), respectively. Furthermore, Raman spectroscopy was used to characterize the interaction between polysaccharide and carbon counterparts. Methotrexate was physically loaded onto the nanohybrid and the release profiles showed a pH-responsive behavior with higher and faster release in acidic (pH 5.0) vs. neutral (pH 7.4) environments. Empty nanoparticles were found to be highly biocompatible in either healthy (MRC-5) or cancerous (H1299) cells, with the nanocarrier being effective in reducing the drug toxicity on MRC-5 while enhancing the anticancer activity on H1299

Temperature induced change of conformation of Sc2TbN@C80 on h-BN/Ni(111)

The conformation of molecules on surfaces is decisive for their functionality. For the case of the endofullerene paramagnet Sc2TbN@C80 the conformation is linked to an electric and a magnetic dipole moment. Therefore a workfunction change of a substrate with adsorbed molecules, qualifies the system to be magnetoelectric. One monolayer of Sc2TbN@C80 has been studied on h-BN/Ni(111). The molecules assume a hexagonally close packed lattice aligned with the substrate high symmetry directions. The structure is incommensurate and arranges at a periodicity of about 4.3x4.3 substrate unit cells. At low temperatures a (2 x 2) superstructure is observed. Angular resolved valence band photoemission spectroscopy shows a temperature induced 0.3 eV shift on the C80 molecular orbitals to lower binding energies that is parallel to a workfunction increase. From comparison of the molecular orbital angular photoemission intensity distributions it is conjectured that the molecules undergo a change in conformation between 30 and 300 K. This phase transition is centred at 125 K as observed with high resolution x-ray photoelectron spectroscopy that shows the core levels of the atomic species on the molecules to shift parallel to the workfunction. The temperature dependence of the workfunction can be described with a two level model that accounts for the disordering with an excitation energy of 60 meV into a highly degenerate ensemble. The experimental findings are backed by density functional theory calculations for the diamagnetic sibling of Sc2TbN@C80 : Sc2YN@C80 that rationalize the incommensurate structure, show a permanent dipole moment of Sc2YN@C80 and a relation between the workfunction and the orientation of the endohedral cluster.Comment: 7 pages 6 figure

Electrostatic Interaction across a Single-Layer Carbon Shell

International audienceIons inside of fullerene molecules are model systems for the study of the electrostatic interaction across a single layer of carbon. For TbSc2N@C80 on h-BN/Ni(111), we observe with high-resolution X-ray photoelectron spectroscopy a splitting of the C 1s core level. The data may be explained quantitatively with density functional theory. The correlation of the C 1s eigenvalues and the Coulomb potential of the inside ions at the corresponding carbon sites indicates incomplete screening of the electric field due to the endohedral ions. The screening comprises anisotropic charge transfer to the carbon atoms and their polarization. This behavior is essential for the ordering of endohedral single-molecule magnets and is expected to occur in any single-layer material

Electrostatic Interaction across a Single-Layer Carbon Shell

Ions inside of fullerene molecules are model systems for the study of the electrostatic interaction across a single layer of carbon. For TbSc2N@C80 on h-BN/Ni(111), we observe with high-resolution X-ray photoelectron spectroscopy a splitting of the C 1s core level. The data may be explained quantitatively with density functional theory. The correlation of the C 1s eigenvalues and the Coulomb potential of the inside ions at the corresponding carbon sites indicates incomplete screening of the electric field due to the endohedral ions. The screening comprises anisotropic charge transfer to the carbon atoms and their polarization. This behavior is essential for the ordering of endohedral single-molecule magnets and is expected to occur in any single-layer material

Fluoroscopically guided thin needle aspiration biopsy of the abdomen and retroperitoneum

The results of 49 transabdominal and translumbar thin needle percutaneous aspiration biopsies in patients suspected of having malignant disease are reported. A correct diagnosis was obtained in 40 cases. Placement of the Chiba needle was accomplished by fluoroscopically controlled biplane radiography during constrast examinations. No complications were encountered. The technique allows cytologic diagnosis of malignancy without high risk exploratory surgery, prolonged hospitalization, or delay of treatment. Use of fluoroscopic needle guidance and biplane radiography for confirmation of position using various contrast examinations as markers is felt to be superior to either CT or ultrasound. The technique is readily available in all radiology departments