C. Casieri

Pore-size evaluation by single-sided nuclear magnetic resonance measurements: Compensation of water self-diffusion effect on transverse relaxation

The determination of penetration depth and distribution of water at surfaces is essential to knowledge of the state of conservation of Cultural Heritage items and materials, such as frescoes, stone, brick, wood, and paper. Water can penetrate the surface of an object, coming from either an external or an internal source, and in general the moisture content of the surface region is the cause of various decay phenomena such as microfractures and disintegration. The nuclear magnetic resonance (NMR) approach can be very powerful for the evaluation of the state of fine arts materials. Not only the water saturation and∕or the porosity of the material can be evaluated but also information on material pore-size distributions can be obtained by monitoring the distributions of relaxation times of the transverse (T2) and longitudinal (T1) components of the H1 magnetization of the trapped water. The drawback is that generally the sample does not fit into standard NMR magnets, and for in situ application, single-sided...

Self-diffusion coefficient by single-sided NMR

It is presented a novel method for the measure of the self-diffusion coefficient. The method exploits the fixed gradient of an open magnet, as that used in single-sided NMR, and it does not use prior information on T(2). The approach presented in this paper can be practiced also on the fringe field of superconducting magnets and it is based on the construction of the ratios between echoes taken at different interpulses separation in a Carr-Purcell-Meiboom-Gill pulse sequence. The determination of the self-diffusion coefficient facilitates the estimate of T(2) because the transverse relaxation results almost influenced by the molecular diffusion effect, also at the shorter interpulses time, when it is measured in field strongly inhomogeneous.

Two-dimensional longitudinal and transverse relaxation time correlation as a low-resolution nuclear magnetic resonance characterization of ancient ceramics

Longitudinal and transverse relaxation time correlation (T1-T2) is employed as a nuclear magnetic resonance noninvasive characterization tool for archeological ceramics. This paper is aimed at investigating whether the most relevant firing-induced changes in ceramics, including those involving pore space properties and paramagnetic mineral structures, could be used as markers of the firing process and therefore of ceramics themselves. Ancient ceramics are made up of naturally available clays, often rich in iron impurities, which undergo relevant modifications of pore distribution upon firing. The firing process also assists chemical and physical rearrangement of iron-bearing species, yielding mineral structures with different magnetic properties. That being so, T1-T2 maps are expected to show the interdependence between ceramic structure and firing technology. T1 and T2 distributions are basically proportional to pore-size distribution, but T2, which is also sensitive to magnetic susceptibility effects, m...

Orientational disordering of the CH4Kr mixture induced by spin conversion at T <1 K.

Abstract Measurements of the longitdinal relaxation time T l in the solid CH 4 ue5f8Kr mixture at low temperatures indicate that the orientationally ordered structure with 33% Kr is modified to a disordered phase by nuclear spin conversion as predicted by the Kyoto group.

Double-resonance J-edited 1H-NMR detection of [6-13C]-D-2-deoxyglucose uptake in glioma cells

The C6 methylene protons were selectively detected in 1H‐NMR spectra of intact glioma cells incubated with [6‐13C]‐D‐2‐deoxyglucose ([6‐13C]‐2dG), a 13C‐enriched glucose analog that is suitable for monitoring glucose utilization in brain tumors. Spectral editing via 1H–13C scalar coupling was performed with twin spin‐echo double resonance (T‐SEDOR), a pulse sequence which combines chemical specificity and high sensitivity, requires no solvent pre‐saturation, and can easily be adapted to imaging protocols. This work demonstrates the suitability of the pulse sequence for monitoring [6‐13C]‐2dG uptake in living cells in vitro, in spite of line‐broadening and the occurrence of other strong signals in the spectral region of interest (3.5–4.4u2005ppm). Copyright

In vivo detection of 13C-enriched glucose metabolites in mouse brain by T-SEDOR imaging

Protons J-coupled to 13C were selectively detected in the mouse head by in vivo 1H NMR imaging based on Twin Spin Echo DOuble Resonance (T-SEDOR) excitation. This pulse sequence combines a good chemical specificity with high sensitivity, requires no solvent pre-saturation and is well adapted to the imaging modality. 1H T-SEDOR maps of the mouse head allowed detection of areas of preferential accumulation of 13C-enriched compounds, upon repeated injections of uniformly 13C-labelled glucose, which induced hyperglycemia. The results demonstrated the feasibility, both in time scale and metabolite concentration, of applying T-SEDOR MRI for in vivo mapping brain areas characterized by enhanced rates of glucose uptake and/or accumulation of its metabolites.

Water confined in nanopores: Spontaneous formation of microcavities

Molecular dynamics simulations of water confined in nanometer sized, hydrophobic channels show that water forms localized cavities for pore diameter

Dipolar and chemical shift anisotropy relaxation in a solid polymer measured by the NMR coherence time in the rotating frame

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Spin interaction filter in solid-state NMR Imaging.

. The cavities present nonspherical shape and lay preferentially adjacent to the confining wall inducing a peculiar form to the liquid exposed surface. The regime of localized cavitation appears to be correlated with the formation of a vapor layer, as predicted by the Lum-Chandler-Weeks theory [J. Phys. Chem. B 103, 4570 (1999)], implying partial filling of the pore.

1H NMR detection of 13C–1H bonds by double 13C editing: application to the discrimination of glucose metabolites

Abstract In this paper a new approach is proposed to the study of slow dynamics in solid complex systems, such as solid polymer or dense macromolecular aggregates. The peculiar aspect of this method is its ability to separate the relaxation contribution coming from the NMR interactions, which are commonly found in such systems, namely the direct dipolar coupling and chemical shift anisotropy. In this approach, the effect of such interactions on relaxation are, to some extent, separable and observable experimentally vs. temperature and vs. the effective resonant frequency. This is realised by measuring the coherence time in the rotating frame T2ρ, which is an unusual NMR parameter whose behaviour is strictly related to the orientation of a tilted rotating frame with respect to the Zeeman field axis. Such an orientation drives the role of the secular part of spin Hamiltonian and makes it controllable experimentally. Thus `fine interaction effects, like the chemical shift one, may be observed to overcome the main effect of the stronger direct dipolar interaction.