Search results for " Spin"
showing 10 items of 1036 documents
Solid state NMR investigation of the roman Acqualadroni rostrum: tenth year assessment of the consolidation treatment of the wooden part
2020
Abstract: This work follows a previous one dealing with the state of conservation study of the wooden part of the roman Acqualadroni rostrum soon after its finding in the seabed of Acqualadroni (Messina, Italy). The archaeological survey and recovery were particularly relevant since this artefact is one of the two rostrums, nowadays known,found together with its wooden part. Following the recovery, it was consolidated by immersion in a melamine-formaldehyde resin (Kauramin) aqueous solution for eight months at the “Centro di Restauro del Legno Bagnato” (Pisa, Italy). The present investigation is aimed to determine at microscopic scale the wood state of conservation and to highlight interact…
Incorporating in vivo and ex vivo NMR sources of information for modeling robust brain tumor classifiers
2010
The purpose of this paper is to investigate the potential and limitations of using multimodal sources of information coming from in vivo NMR and ex vivo NMR data for detecting brain tumors. Supervised pattern recognition methods, whose performance directly depends on the prior available observations used in building them, are proposed. We show that high resolution magic angle spinning (HR-MAS) data act as complementary information for classifying magnetic resonance spectroscopic imaging (MRSI) data. In particularly, when considering rare brain tumors, since it is unlikely to acquire sufficient cases to define their metabolite profiles using only in vivo NMR information, HR-MAS can support t…
Quantifying brain tumor tissue abundance in HR-MAS spectra using non-negative blind source separation techniques
2012
Given high-resolution magic angle spinning (HR-MAS) spectra from several glial tumor subjects, our goal is to differentiate between tumor tissue types by separating the different sources that contribute to the profile of each spectrum. Blind source separation techniques are applied for obtaining characteristic profiles for necrosis, highly cellular tumor and border tumor tissue and providing the contribution (abundance) of each of these tumor tissue types to the profile of each spectrum. The problem is formulated as a non-negative source separation problem. Non-negative matrix factorization, convex analysis of non-negative sources and non-negative independent component analysis methods are …
Interplay between spin-crossover and luminescence in a multifunctional single crystal iron( ii ) complex: towards a new generation of molecular senso…
2019
Multifunctional mononuclear iron( ) complex coordinated with six phosphorescent ligands exhibiting correlated spin-crossover transition and enhanced fluorescence.
Tripartite thermal correlations in an inhomogeneous spin-star system
2010
We exploit the tripartite negativity to study the thermal correlations in a tripartite system, that is the three outer spins interacting with the central one in a spin-star system. We analyze the dependence of such correlations on the homogeneity of the interactions, starting from the case where central-outer spin interactions are identical and then focusing on the case where the three coupling constants are different. We single out some important differences between the negativity and the concurrence.
Non-Markovian master equation for the XX central spin model
2008
The non-Markovian correlated projection operator technique is applied to the model of a central spin coupled to a spin bath through non uniform XX Heisenberg coupling. The second order results of the Nakajima-Zwanzig and of the time-convolutionless methods are compared with the exact solution considering a fully polarized initial bath state.
Spin Cross-Over (SCO) Complex Based on Unsymmetrical Functionalized Triazacyclononane Ligand: Structural Characterization and Magnetic Properties
2019
International audience; The unsymmetrical ligand 1-(2-aminophenyl)-4,7-bis(pyridin-2-ylmethyl)-1,4,7-triazacyclononane (L6) has been prepared and characterized by NMR spectroscopy. The L6 ligand is based on the triazamacrocycle (tacn) ring that is functionalized by two flexible 2-pyridylmethyl and one rigid 2-aminophenyl groups. Reaction of this ligand with Fe(ClO4)2·xH2O led to the complex [Fe(L6)](ClO4)2 (1), which was characterized as the first Fe(II) complex based on the unsymmetrical N-functionalized tacn ligand. The crystal structure revealed a discrete monomeric [FeL6]2+ entity in which the unsymmetrical N-functionalized triazacyclononane molecule (L6) acts as hexadentate ligand. As …
Solid state NMR studies of gels derived from low molecular mass gelators
2016
The emergence of NMR crystallography provides a unique opportunity to study solids, gels and xerogels, thereby providing ample information to elucidate molecular packing in the native gel. This review details the importance as well as the application of solid state NMR spectroscopy combined with other analytical tools to study gels derived from low molecular mass organo- and hydrogelators.
Spin Crossover in Fe(II) Molecular Compounds — Mössbauer and µSR Investigations
2002
The compound [Fe(ptz)6](C104)2 (ptz = 1-propyl-tetrazole) displays a complete and gradual spin crossover centred around 125 K as evidenced by magnetic and muon measurements over the temperature range ∼ 4.2–300 K. Although the crystal structure reveals only one crystallographic site, line broadening is observed in the Mossbauer spectra in the vicinity of the spin transition. The muon spin relaxation behaviour of this compound indicates that a structural transformation rather than dynamic processes may account for the observed spectral features. Both the Mossbauer and muon measurements are consistent with a mixture of high and low spin Fe ions in the transition region.
Heavy-quark spin symmetry for charmed and strange baryon resonances
2013
We study charmed and strange odd-parity baryon resonances that are generated dynamically by a unitary baryon-meson coupled-channels model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg-Tomozawa chiral Lagrangian to SU(8) spin-flavor symmetry plus a suitable symmetry breaking. The model generates resonances with negative parity from the s-wave interaction of pseudoscalar and vector mesons with 1/2(+) and 3/2(+) baryons in all the isospin, spin, and strange sectors with one, two, and three charm units. Some of our results can be identified with experimental data from several facilities, such as the CLEO, Belle, or BaBar Collaborations, as we…