Nuclear spin relaxation in aqueous paramagnetic ion solutions.

A Brownian shell model describing the random rotational motion of a spherical shell of uniform particle density is presented and validated by molecular dynamics simulations. The model is applied to proton spin rotation in aqueous paramagnetic ion complexes to yield an expression for the Larmor-frequency-dependent nuclear magnetic resonance spin-lattice relaxation rate T_{1}^{-1}(ω) describing the dipolar coupling of the nuclear spin of the proton with the electronic spin of the ion. The Brownian shell model provides a significant enhancement to existing particle-particle dipolar models without added complexity, allowing fits to experimental T_{1}^{-1}(ω) dispersion curves without arbitrary scaling parameters.

Advanced insight on the water dynamics of anisotropic hydrogels by field-cycling nuclear magnetic resonance: Application of 3-Tau model.

Fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry is used to investigate an anisotropic polygalacturonate hydrogel formed by the diffusion of calcium ions from an external reservoir (external gelation). Such a hydrogel has a gradient of polymer density accompanied by a gradient of the mesh size of its 3D network. The NMR relaxation process is dominated by the interaction of proton spins between water molecules located at polymer interfaces and in nanoporous spaces.

Distributed Tactile Display with Dual Array Design.

It is well-accepted that designing and manufacturing distributed tactile displays is hard owing to difficulties associated with packing many strong actuators in a small space. We explored a new design for such displays by reducing the number of independently actuated degrees of freedom while preserving the ability to decorrelate the signals applied to small regions of the fingertip skin inside the contact area. The device comprised two independently actuated tactile arrays so the degree of correlation of the waveforms stimulating those small regions could be globally controlled.

Monitoring the Effect of Calcium Nitrate on the Induction Period of Cement Hydration via Low-Field NMR Relaxometry.

The hydration process of Portland cement is still not completely understood. For instance, it is not clear what produces the induction period, which follows the initial period of fast reaction, and is characterized by a reduced reactivity. To contribute to such understanding, we compare here the hydration process of two cement samples, the simple cement paste and the cement paste containing calcium nitrate as an accelerator.

Water as a Lévy Rotor.

A probability density function describing the angular evolution of a fixed-length atom-atom vector as a Lévy rotor is derived containing just two dynamical parameters: the Lévy parameter α and a rotational time constant τ. A Lévy parameter α<2 signals anomalous (non-Brownian) motion. Molecular dynamics simulation of water at 298 K validates the probability density function for the intramolecular ^{1}H─^{1}H dynamics.