Search results for " inversion"
showing 10 items of 167 documents
Atypical liver hemangiomas: contrast enhancement patterns with SH U 508A and pulse inversion ultrasound
2003
A new proof of the support theorem and the range characterization for the Radon transform
1983
The aim of this note is to give a new and elementary proof of the support theorem for the Radon transform, which is based only on the projection theorem and the Paley-Wiener theorem for the Fourier transform. The idea is to solve a certain system of linear equations in order to determine the coefficients of a homogeneous polynomial (interpolation problem). By the same method, we get a short proof of the range characterization for Radon transforms of functions supported in a ball.
Chiral Inversion of Thiolate-Protected Gold Nanoclusters via Core Reconstruction without Breaking an Au-S Bond
2019
On the basis of density functional theory computations of the well-known chiral Au38(SR)24 nanocluster and its Pd- and Ag-doped derivatives, we propose here a mechanism for chiral inversion that does not require the breaking of a metal-sulfur bond at the metal-ligand interface but features a collective rotation of the gold core. The calculated energy barriers for this mechanism for Au38 and Pd-doped Au38 are in the range of 1-1.5 eV, significantly lower than barriers involving the breakage of Au-S bonds (2.5 eV). For Ag-doped Au38, barriers for both mechanisms are similar (1.3-1.5 eV). Inversion barriers for a larger chiral Au144(SR)60 are much higher (2.5-2.8 eV). Our computed barriers are…
Crustal Structure of the Seismogenic Volume of the 2010–2014 Pollino (Italy) Seismic Sequence From 3D P- and S-Wave Tomographic Images
2021
A tomographic analysis of Mt. Pollino area (Italy) has been performed using earthquakes recorded in the area during an intense seismic sequence that occurred between 2010 and 2014. 870 local earthquakes with magnitude ranging from 1.8 to 5.0 were selected considering the number of recording stations, the signal quality, and the hypocenter distribution. P- and S-wave arrival times were manually picked and used to compute 3D velocity models through tomographic seismic inversion. The resulting 3D distributions of VP and VS are characterized by high resolution in the central part of the investigated area and from surface to about 10 km below sea level. The aim of the work is to obtain high-qual…
Faults role in geological processes. Repeated changing of activity mode and magnitude fron basin formation to mountain belt staking: the case of the …
2010
Le violazioni inerenti agli obblighi di documentazione, di registrazione e di individuazione di determinati prodotti, alle operazioni non imponibili …
2011
Commento delle norme sanzionatorie relative alle violazioni inerenti agli obblighi di emissione di documenti fiscali in materia di imposta sul valore aggiunto, compresi quelli relativi al regime monofase nel settore delle telecomunicazioni e quelli riferibili alla documentazione nel regime dell'inversione contabile
Libre circulación de inversiones en la Unión Europea en tiempos de COVID-19
2020
Las inversiones extranjeras han fluido como nunca durante las últimas décadas, en el marco de una aceptación generalizada de sus beneficios. Esta situación, sin embargo, comienza a alterarse de forma acelerada en múltiples lugares del planeta. La presencia de un entorno geoestratégico más complejo y la aproximación crítica de muchos Estados hacia la globalización y lo que ella significa, está consolidando una visión más cautelosa hacia la libre circulación de inversiones extranjeras que, entre otros efectos, se plasma en la elaboración de normativas más restrictivas. La Unión Europea es un espacio económicamente integrado, muy abierto a las inversiones extranjeras y dotado además, de una po…
Deep Gaussian processes for biogeophysical parameter retrieval and model inversion
2020
Parameter retrieval and model inversion are key problems in remote sensing and Earth observation. Currently, different approximations exist: a direct, yet costly, inversion of radiative transfer models (RTMs); the statistical inversion with in situ data that often results in problems with extrapolation outside the study area; and the most widely adopted hybrid modeling by which statistical models, mostly nonlinear and non-parametric machine learning algorithms, are applied to invert RTM simulations. We will focus on the latter. Among the different existing algorithms, in the last decade kernel based methods, and Gaussian Processes (GPs) in particular, have provided useful and informative so…
Zur Stereochemie der Oxidation chiraler, tertiärer Phosphine mit Dimethylsulfoxid
1976
Es wird uber den sterischen Verlauf der Oxidation der optisch aktiven, tertiaren Phosphine 3 and 4 mit Dimethylsulfoxid berichtet. Diese Umsetzung verlauft nur in Gegenwart elektrophiler Katalysatoren (Tabelle 1). Je nach Art and Menge des Katalysators zeigt die Stereochemie der Reaktion entweder uberwiegende Inversion oder Retention der Konfiguration am Phosphor an (Tabellen 2, 3); in einigen Fallen wird jedoch fast vollstandige Racemisierung beobachtet (Tabelle3). Auf der Grundlage dieser stereochemischen Resultate werden mogliche Mechanismen fur diese Umsetzung diskutiert. The Sterochemistry of the Oxidation of Chiral Tertiary Phosphines by Means of Dimethyl Sulfoxide The steric course o…
The in, out Asymmetric Pseudo-Triple Helical Form of a D3h Diaza-Macropentacycle
2007
A sterically encumbered [N(2)S(6)] macropentacycle (5) related to diazamacrobicycles and cryptands has been synthesized in 53% yield by the [1+1] condensation reaction between functionalized macrocyclic and macrotricyclic precursors. A macrononacycle (18) resulting from the corresponding [2+2] condensation was isolated in 7% yield from the reaction mixture. Both compounds showed broad features in their room-temperature (1)H NMR spectra, but their maximal average symmetry (D(3h) and D(2h), respectively) was achieved at high temperature (380 K). At low temperature (200 K, CD(2)Cl(2) solution), the macropentacycle is "frozen" to a single asymmetric (C1) conformation on the (1)H NMR time scale,…