Plasma Response to Resonant Perturbations at Tokamak Edge

In certain circumstances, plasma response suppresses magnetic islands expected at perturbed resonant magnetic surfaces. We investigate the plasma response to the resonant magnetic perturbations in a large aspect ratio tokamak perturbed by external resonant helical windings, considering polar toroidal coordinates for which analytical toroidal equilibrium solutions and perturbing fields are available. We apply an empirical approach to mimic the plasma screening effects by introducing presumed plasma current sheets on the resonance surfaces to cancel the RMP effects. Numerical examples show the effect of plasma response reducing magnetic islands at the plasma edge and also regularizing field lines around the resonant surface. The distribution of connection lengths along the plasma cross section indicates that the plasma response increases the connection lengths since more toroidal turns are performed until a field line reaches the tokamak wall.     

Lefschetz Complex Conditions for Complex Manifolds

For any compact complex manifold M with a compatible symplectic form, we consider the homomorphisms L _1,0: H ^1,0(M) H ^{{n, n–1}(M) and L _{0, 1}: H ^{0, 1}(M) H ^{n – 1, n} (M) given by the cup product with [] ^{n – 1}, n being the complex dimension of M andH ^{*, *}(M) the Dolbeault cohomology of M. We say that Mhas Lefschetz complex type (1, 0) (resp. (0, 1)) if L _{1, 0} (resp.L _{0, 1}) is injective. Such conditions can be considered as complexversions of the (real) Lefschetz condition studied by Benson and Gordonin [Topology 27 (1988), 513–518]for symplectic manifolds. Within the class of compactcomplex nilmanifolds, we prove that the injectivity of L _{1, 0}characterizes those complex structures which are Abelian in the sense ofBarberis et al. [Ann. Global Anal. Geom. 13 (1995), 289–301]. In contrast, complex tori are the only nilmanifolds having Lefschetz complex type (0, 1).     

Non-haloaluminate room-temperature ionic liquids in electrochemistry--a review.

Some twenty-five years after they first came to prominence as alternative electrochemical solvents, room temperature ionic liquids (RTILs) are currently being employed across an increasingly wide range of chemical fields. This review examines the current state of ionic liquid-based electrochemistry, with particular focus on the work of the last decade. Being composed entirely of ions and possesing wide electrochemical windows (often in excess of 5 volts), it is not difficult to see why these compounds are seen by electrochemists as attractive potential solvents. Accordingly, an examination of the pertinent properties of ionic liquids is presented, followed by an assessment of their application to date across the various electrochemical disciplines, concluding with an outlook viewing current problems and directions.     

Electron-energy-loss and X-ray photoelectron spectra. Part 1. Electronic structure of tetraphenylporphyrin and its nickel derivative

Specific information on the energy level diagram and on the energy forbidden gap of tetraphenylporphyrin and its Ni derivative has been obtained by means of electron energy-loss spectroscopy (EELS) and X-ray photoelectron spectroscopy techniques. Comparison of the free ligand and its metal derivative emphasizes the importance of the metal 3d levels in the conduction processes. The interband and plasmon transition present in the EELS spectra of these species are compared with the theoretically calculated energy level diagram and experimental data.     

Raman spectroscopic analysis of a tembetá: a resin archaeological artefact in need of conservation

The Raman spectroscopic analysis of a Brazilian tembetá, a lip-plug which signifies the attainment of manhood in tribal cultures, and dated to about 1600 years BP is reported. Tembetá are usually made of wood or stone but this lip-plug is very rare in that it is made of resin, which has been severely degraded in the burial environment; the brownish-red fragmented remains are in an extremely fragile condition and information about the chemical composition was required before urgent conservation was undertaken. Raman spectra excited at 1064 nm showed the presence of triterpenoid materials in the main body of the artefact, and indicated that the red-brown coating was not iron(III) oxide as suspected but rather degraded resin. Comparison with contemporary resins has facilitated the partial identification of the material in this important artefact as a triterpenoid-rich material, which is closely similar to the Pistacia species. A possible archaeological link to the Jatobá do Cerrado (Hymenaea stigonocarpa Mart.) resin has been excluded as the Raman spectra of this resin specimen and the tembetá do not match; indeed, the Jatobá do Cerrado resin specimen belongs to a diterpenoid-rich classification as befits its Hymenaea species.