Multispin moments edited by multiple-quantum NMR: application to elastomers.

The spin system response to the five-pulse sequence used for measurements of double-quantum and triple-quantum buildup curves is evaluated in the initial excitation/reconversion regime. The multispin dipolar network that is present also in many soft solids like elastomers was considered. It is proved rigorously that the relevant quantity for analysis of double-quantum build-up curves in the initial regime is the second van Vleck moment. The higher-order moments edited by double-quantum as well as higher-order coherences in the multiple-quantum build-up experiments are different from van Vleck moments. These results can be applied to compare (1)H residual moments edited by double-quantum and triple-quantum experiments with those measured by other NMR methods. The sensitivity of multiple-quantum coherences to the changes in the values of residual dipolar couplings for cross-linked natural rubber under uniaxial elongation is also discussed. Under such conditions (1)H second van Vleck moments were measured for different elongation ratios of a cross-linked natural rubber. Moreover, (1)H triple-quantum edited moments were also measured for the same sample under uniaxial compression. The dependence of the second van Vleck moment and the time of the maximum of the double-quantum buildup curve on the cross-link density of natural rubber measured at low magnetic field was also investigated.

A therapeutic splint for hypertonic flexed elbow in upper motor neuron diseased patients.

Change in muscle tonus is characteristic of upper motor neuron disease. Upper limb hypertonus is mostly experienced in the flexor muscles group, causing abnormal fixed flexion of the elbow. This in turn leads to functional impairments in daily life (especially in stability while standing and walking, and in activities such as dressing), often accompanied by chronic pain. Extension of the spastic elbow is therefore a significant target goal of the rehabilitation process of these patients. This study presents the development of a simple, cheap and easy-to-use splint aimed at keeping the elbow extended. The splint is made out of cloth and plastic strips with longitudinal pockets sown into a double layer cloth surface. The splint is then wrapped and tightened around the extended elbow. The splint was applied to 30 patients with hypertonic flexed elbow. Patients were asked to keep the splint wrapped around their elbows between one to five hours a day, for a period of three weeks. They were instructed to shorten the time of use whenever they felt pain, discomfort or extended pressure on the arm. Most of the patients completed the trial as instructed and expressed their wish to carry on using it. The reported "side effects" included discomfort, feeling of pressure at the critical points and difficult self-application of the splint. The final splint model was developed based on this feedback. Its efficacy in keeping the elbow in an extended position, its low cost price and easy use makes this splint a viable and simple tool for the rehabilitation process of upper motor neuron disease patients.

Anti-Stokes laser cooling in Yb(3+)-doped KPb(2) Cl(5) crystal.

We report internal laser cooling in Yb(3+) -doped KPb(2)Cl(5) . From the quantum efficiency values measured in the heating and cooling regions by use of the photothermal deflection technique, we have obtained a room-temperature cooling efficiency of 0.2% in a sample doped with ~5x10(19)ions/cm(3) . Excitation spectra obtained under high irradiation fluences show an excess of fluorescence with regard to those obtained at low fluences, which agrees with the prediction of a model based on photon-ion-phonon interaction.