An Alternative Construction of the Quantum Action for Supergravity

We develop a method to derive the on-shell invariant quantum action of the supergravity in such a way that the quartic ghost interaction term is explicity determined. First, we reinvestigate the simple supergravity in terms of a principal superfibre bundle. This gives rise to the closed geometrical BRST algebra. Therefore we determine the open BRST algebra, which realizes the invariance of the classical action. Then, given a prescription to build the full quantum action, we obtain the quantum BRST algebra. Together with the constructed quantum action this allows us to recover the auxiliary fields and the invariant extension of the classical action.Comment: 17 pages, No figure

On Auxiliary Fields in BF Theories

We discuss the structure of auxiliary fields for non-Abelian BF theories in arbitrary dimensions. By modifying the classical BRST operator, we build the on-shell invariant complete quantum action. Therefore, we introduce the auxiliary fields which close the BRST algebra and lead to the invariant extension of the classical action.Comment: 7 pages, minor changes, typos in equations corrected and acknowledgements adde

The presence of valine at residue 129 in human prion protein accelerates amyloid formation

The polymorphism at residue 129 of the human PRNP gene modulates disease susceptibility and the clinicopathological phenotypes in human transmissible spongiform encephalopathies. The molecular mechanisms by which the effect of this polymorphism are mediated remain unclear. It has been shown that the folding, dynamics and stability of the physiological, alpha-helix-rich form of recombinant PrP are not affected by codon 129 polymorphism. Consistent with this, we have recently shown that the kinetics of amyloid formation do not differ between protein containing methionine at codon 129 and valine at codon 129 when the reaction is initiated from the a-monomeric PrPC-like state. In contrast, we have shown that the misfolding pathway leading to the formation of beta-sheet-rich, soluble oligomer waS favoured by the presence of methionine, compared with valine, at position 129. In the present work, we examine the effect of this polymorphism on the kinetics of an alternative misfolding pathway, that of amyloid formation using partially folded PrP allelomorphs. We show that the valine 129 allelomorph forms amyloids with a considerably shorter lag phase than the methionine 129 allelomorph both under spontaneous conditions and when seeded with pre-formed amyloid fibres. Taken together, our studies demonstrate that the effect of the codon 129 polymorphism depends on the specific misfolding pathway and on the initial conformation of the protein. The inverse propensities of the two allelomorphs to misfold in vitro through the alternative oligomeric and amyloidogenic pathways could explain some aspects of prion diseases linked to this polymorphism such as age at onset and disease incubation time. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved

An Approach To The Defect Structure Analysis Of Lithium Niobate Ilmenite Type Structure

We present in this work a comparative study between the normal and the ilmenite structural of LiNbO3. Namely, the normal cation stacking sequence is replaced by the ilmenite ordering: …Nb Li vacancy Li Nb vacancy Nb Li vacancy Li Nb vacancy…. . From Safaryan’s approach which combines a ferroelectric phase transition theory and vacancy models we allows to calculate the Curie temperature in ilmenite LiNbO3. Comparatively, we showed that the ilmenite structural LiNbO3 is in an excellent agreement with experiment result than the normal LiNbO3We present in this work a comparative study between the normal and the ilmenite structural of LiNbO3. Namely, the normal cation stacking sequence is replaced by the ilmenite ordering: …Nb Li vacancy Li Nb vacancy Nb Li vacancy Li Nb vacancy…. . From Safaryan’s approach which combines a ferroelectric phase transition theory and vacancy models we allows to calculate the Curie temperature in ilmenite LiNbO3. Comparatively, we showed that the ilmenite structural LiNbO3 is in an excellent agreement with experiment result than the normal LiNbO