Search results for "SHIFT"
showing 10 items of 1226 documents
Nonlocalization Properties of Time Operators Transformations
2014
It is presented a general approach to the problem of extension of time operators and the associated Lambda transformations on singular measures. It is also shown that Lambda transformations defined on function spaces having the Urysohn property are non localized. Particular attention has been devoted to time and Lambda operators associated with the Walsh-Paley system and to a characterization of their domain and non locality.
Elliptic convolution operators on non-quasianalytic classes
2001
For those nonquasianalytic classes in which an extension of the classical Borel's theorem holds we show that every elliptic convolution operator is the composition of a translation and an invertible ultradifferential operator. This answers a question asked by Chou in: La transformation de Fourier complexe et l'equation de convolution, LNM 325, Berlin-Heidelberg-New York (1973).
Waveguiding properties of a photonic crystal fiber with a solid core surrounded by four large air holes
2009
The polarization-dependent guiding properties of a hexagonal-lattice photonic crystal fiber with a solid-core surrounded by four large air holes are investigated. The appearance of a polarization dependent cutoff frequency, together with several parameters as the birefringence, the modal effective area, the group velocity dispersion and the polarization dependent loss are analyzed. A collection of fibers with different structural parameters were fabricated and characterized. An effective anti-guide structure from at least 450 nm to 1750 nm, a polarizing fiber with a polarization dependent loss of 16 dB/m at 1550 nm, and an endlessly singlemode polarization-maintaining fiber with group biref…
Sensitivity optimization with cladding-etched long period fiber gratings at the dispersion turning point
2016
This work presents a refractive index sensor based on a long period fiber grating (LPFG) made in a reduced cladding fiber whose low order cladding modes have the turning point at large wavelengths. The combination of these parameters results in an improved sensitivity of 8734 nm/refractive index unit (RIU) for the LP0,3 mode in the 1400-1650 wavelength range. This value is similar to that obtained with thin-film coated LPFGs, which permits to avoid the coating deposition step. The numerical simulations are in agreement with the experimental results. This work was supported in part by the Spanish Ministry of Education and Science-FEDER TEC2013-43679-R. J.L. Cruz also acknowledges financial s…
Multioctave midinfrared supercontinuum generation in suspended-core chalcogenide fibers
2014
An As2S3 fiber-based supercontinuum source that covers 3500 nm, extending from near visible to the midinfrared, is successfully reported by using a 200-fs-pulsed pump with nJ-level energy at 2.5 μm. The main features of our fiber-based source are two-fold. On the one hand, a low-loss As2S3 microstructured optical fiber has been fabricated, with typical attenuation below 2 dB/m in the 1-4 μm wavelength range. On the other hand, a 20-mm-long microstructured fiber sample is sufficient to enable a spectral broadening, spreading from 0.6 to 4.1 μm in a 40 dB dynamic range.
Alla ricerca dei fattori rilevanti nell’adozione dei sistemi di gestione della performance nelle amministrazioni pubbliche territoriali. L’analisi di…
2013
La ricerca scientifica ha dimostrato che la gestione della performance nelle amministrazioni pubbliche sta oggi spostando il proprio focus dalla mera attività di raccolta e rendicontazione di dati alla generazione di informazioni atte a supportare la formulazione di decisioni. L’analisi comparativa dei casi di studio analizzati in questo articolo mira ad identificare i fattori critici sottostanti alla progettazione e all’utilizzo dei sistemi di gestione della performance nelle amministrazioni regionali. Da questa analisi emerge che alcune variabili risultano essenziali ai fini di un’efficace adozione dei sistemi di performance management. Tra queste variabili sono annoverabili: il ruolo del…
Understanding the ring current effects on magnetic shielding of hydrogen and carbon nuclei in naphthalene and anthracene
2008
The local response to an external magnetic field normal to the molecular plane of naphthalene and anthracene was investigated via current density and magnetic shielding density maps. The Biot-Savart law shows that the deshielding caused by pi-ring currents in naphthalene is stronger for alpha- than for beta-protons due to geometrical factors. The shielding tensor of the carbon nuclei in both molecules is strongly anisotropic and its out-of-plane component determines the up-field chemical shift of (13)C in nuclear magnetic resonance spectra. The pi-ring currents flowing beyond the C-skeleton in front of a probe carbon nucleus, and on remote parts of the molecular perimeter, yield positive co…
Simplification, not “tropicalization”, of temperate marine ecosystems under ocean warming and acidification
2021
Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed “tropicalization”. A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral-dominated systems…
Climate change and the ecology and evolution of Arctic vertebrates.
2012
25 pages; International audience; Climate change is taking place more rapidly and severely in the Arctic than anywhere on the globe, exposing Arctic vertebrates to a host of impacts. Changes in the cryosphere dominate the physical changes that already affect these animals, but increasing air temperatures, changes in precipitation, and ocean acidification will also affect Arctic ecosystems in the future. Adaptation via natural selection is problematic in such a rapidly changing environment. Adjustment via phenotypic plasticity is therefore likely to dominate Arctic vertebrate responses in the short term, and many such adjustments have already been documented. Changes in phenology and range w…
DNA fluorescence induced by polymethine cation pyrvinium binding
1991
Pyrvinium is a polymethine cation which shows interesting fluorescence emission and DNA binding properties. In diluted aqueous solution, pyrvinium pamoate induced a bright yellow fluorescence in kinetoplast DNA from Trypanosoma cruzi epimastigotes as well as in chicken erythrocyte nuclei under a wide range of excitations. No fading was observed after mounting in suitable media. Spectroscopic studies on pyrvinium solutions revealed bathochromic and hypochromic shifts in the absorption spectrum of its complex with DNA. A striking enhancement of pyrvinium fluorescence was found in solvents of high viscosity or after binding to DNA. Experimental results and the chemical structure of pyrvinium a…