Spectral decomposition for the Dirac system associated to the DSII equation

A new (scalar) spectral decomposition is found for the Dirac system in two dimensions associated to the focusing Davey--Stewartson II (DSII) equation. Discrete spectrum in the spectral problem corresponds to eigenvalues embedded into a two-dimensional essential spectrum. We show that these embedded eigenvalues are structurally unstable under small variations of the initial data. This instability leads to the decay of localized initial data into continuous wave packets prescribed by the nonlinear dynamics of the DSII equation

Free Boundary Poisson Bracket Algebra in Ashtekar's Formalism

We consider the algebra of spatial diffeomorphisms and gauge transformations in the canonical formalism of General Relativity in the Ashtekar and ADM variables. Modifying the Poisson bracket by including surface terms in accordance with our previous proposal allows us to consider all local functionals as differentiable. We show that closure of the algebra under consideration can be achieved by choosing surface terms in the expressions for the generators prior to imposing any boundary conditions. An essential point is that the Poisson structure in the Ashtekar formalism differs from the canonical one by boundary terms.Comment: 19 pages, Latex, amsfonts.sty, amssymb.st

Combining scanning probe microscopy and x-ray spectroscopy

A new versatile tool, combining Shear Force Microscopy and X-Ray Spectroscopy was designed and constructed to obtain simultaneously surface topography and chemical mapping. Using a sharp optical fiber as microscope probe, it is possible to collect locally the visible luminescence of the sample. Results of tests on ZnO and on ZnWO4 thin layers are in perfect agreement with that obtained with other conventional techniques. Twin images obtained by simultaneous acquisition in near field of surface topography and of local visible light emitted by the sample under X-Ray irradiation in synchrotron environment are shown. Replacing the optical fibre by an X-ray capillary, it is possible to collect local X-ray fluorescence of the sample. Preliminary results on Co-Ti sample analysis are presented

Ammonite Faunal Dynamics Across Bio-Events During the Mid-and Late Cretaceous Along the Russian Pacific Coast

Jagt−Yazykova, E.A. 2012. Ammonite faunal dynamics across bio−events during the mid − and Late Cretaceous along th

Spatial resolution of confocal XRF technique using capillary optics

XRF (X-ray fluorescence) is a powerful technique for elemental analysis with a high sensitivity. The resolution is presently limited by the size of the primary excitation X-ray beam. A test-bed for confocal-type XRF has been developed to estimate the ultimate lateral resolution which could be reached in chemical mapping using this technique. A polycapillary lens is used to tightly focus the primary X-ray beam of a low power rhodium X-ray source, while the fluorescence signal is collected by a SDD detector through a cylindrical monocapillary. This system was used to characterize the geometry of the fluorescent zone. Capillary radii ranging from 50 mu m down to 5 mu m were used to investigate the fluorescence signal maximum level This study allows to estimate the ultimate resolution which could be reached in-lab or on a synchrotron beamline. A new tool combining local XRF and scanning probe microscopy is finally proposed

The role of prefixes in the formation of aspectuality. Issues of grammaticalization

Gli studi raccolti nella presente miscellanea si inseriscono nell\u2019ambito delle ricerche tipologiche sull\u2019aspetto verbale e sulla sua grammaticalizzazione e, in particolare, sul ruolo della prefissazione in questo processo. Le lingue pi\uf9 studiate e considerate, in un certo senso \u201cle pi\uf9 prototipiche\u201d per quanto riguarda questa categoria linguistica sono le lingue slave nelle quali i prefissi inizialmente hanno svolto la funzione di concretizzare dal punto di vista spaziale o azionale il verbo, ma successivamente, nel processo diacronico di grammaticalizzazione, hanno acquisito significati pi\uf9 astratti, primo tra i quali la terminativit\ue0 dell\u2019azione, che \ue8 alla base della perfettivit\ue0. Analoghi sviluppi hanno caratterizzato anche altre lingue (non slave, appartenenti al ceppo indo-europeo, ma non solo), pure caratterizzate dalla presenza dei preverbi nel loro sistema verbale ma senza che questo portasse allo sviluppo della categoria dell\u2019aspetto verbale di tipo slavo. Tra gli autori dei contributi si possono annoverare studiosi italiani e stranieri di fama internazionale come P. Arkadiev, R. Benacchio, W. Breu, S.M. Dickey, F. Esvan, J. Kamphuiis, E.V. Petruchina, V. Plungjan, B. Wiemer