Two- and three-dimensional multinuclear stray-field imaging of rotating samples with magic-angle spinning (STRAFI-MAS): from bio to inorganic materials.

PURPOSE: To revisit and illustrate the potential of a simple and effective multidimensional stray-field imaging technique with magic-angle spinning, known as STRAFI-MAS. MATERIALS AND METHODS: STRAFI-MAS images are acquired with a standard NMR magnet and a traditional magic-angle sample spinning (MAS) probe. The stray-field gradients are achieved by placing the MAS probe, along the z-direction, at a distance from the center of the magnet. No pulsed-field gradients are applied. The multidimensional spatial encoding is carried out by synchronizing the radiofrequency pulses with the sample MAS rotation. RESULTS: Two-dimensional (2D) and 3D multinuclear images of various phantoms, including a tibia bone and silicon carbide, are recorded. Images of inorganic solids containing quadrupolar nuclei, (23)Na and (27)Al, are also explored for the first time by STRAFI-MAS. CONCLUSION: We have demonstrated that STRAFI-MAS is a simple and user-friendly technique for multidimensional imaging without the need of imaging equipment. With the current advancements in NMR and MRI methodologies, STRAFI-MAS is expected to be further developed and improved. We anticipate that STRAFI-MAS can spark a wide spectrum of interest, from material to bio science, where can benefit from high-resolution images.

Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy.

Despite the numerous studies of bone mineral, there are still many questions regarding the exact structure and composition of the mineral phase, and how the mineral crystals become organised with respect to each other and the collagen matrix. Bone mineral is commonly formulated as hydroxyapatite, albeit with numerous substitutions, and has previously been studied by (31)P and (1)H NMR, which has given considerable insight into the complexity of the mineral structure. However, to date, there has been no report of an NMR investigation of the other major component of bone mineral, calcium, nor of common minority cations like sodium. Here, direct analysis of the local environment of calcium in two biological apatites, equine bone (HB) and bovine tooth (CT), was carried out using both (43)Ca solid state NMR and Ca K-edge X-ray absorption spectroscopy, revealing important structural information about the calcium coordination shell. The (43)Ca delta(iso) in HB and CT is found to correlate with the average Ca-O bond distance measured by Ca K-edge EXAFS, and the (43)Ca NMR linewidths show that there is a greater distribution in chemical bonding around calcium in HB and CT, compared to synthetic apatites. In the case of sodium, (23)Na MAS NMR, high resolution 3Q-MAS NMR, as well as (23)Na{(31)P} REDOR and (1)H{(23)Na} R(3)-HMQC correlation experiments give the first direct evidence that some sodium is located inside the apatite phase in HB and CT, but with a greater distribution of environments compared to a synthetic sodium substituted apatite (Na-HA).

Forces of various nickel titanium closed coil springs.

OBJECTIVE: To compare the forces generated by 14 different 9 mm springs supplied by five different companies. MATERIALS AND METHODS: Five replicates of 14 different 9 mm springs were evaluated, resulting in 70 total specimens. Each was extended once from its resting length to 12 mm and then was deactivated. All tests were performed in a 37 degrees C water bath. Forces were recorded at the 12 mm extension and deactivation distances of 9 mm, 6 mm, 3 mm, and 1 mm using an MTS force gauge. Data were collected with Testworks software, version 4.0, and were analyzed by analysis of variance (ANOVA) with one factor alternated. RESULTS: Mean peak load forces at 12 mm were significantly different between springs, and these forces varied from 147 to 474 grams. Mean unload forces measured at 9 mm, 6 mm, and 3 mm of deactivation values were highly variable, and only 6 of the 14 springs exhibited a "physiologic" mean unload force of 50 grams or less over the total deactivation range. CONCLUSIONS: Few springs tested exhibited physiologic peak load forces and constant deactivation forces. This study suggests that labeling of nickel titanium closed coil springs is confusing and misleading.

Magnesium incorporation into hydroxyapatite.

The incorporation of Mg in hydroxyapatite (HA) was investigated using multinuclear solid state NMR, X-ray absorption spectroscopy (XAS) and computational modeling. High magnetic field (43)Ca solid state NMR and Ca K-edge XAS studies of a ∼10% Mg-substituted HA were performed, bringing direct evidence of the preferential substitution of Mg in the Ca(II) position. (1)H and (31)P solid state NMR show that the environment of the anions is disordered in this substituted apatite phase. Both Density Functional Theory (DFT) and interatomic potential computations of Mg-substituted HA structures are in agreement with these observations. Indeed, the incorporation of low levels of Mg in the Ca(II) site is found to be more favourable energetically, and the NMR parameters calculated from these optimized structures are consistent with the experimental data. Calculations provide direct insight in the structural modifications of the HA lattice, due to the strong contraction of the M⋯O distances around Mg. Finally, extensive interatomic potential calculations also suggest that a local clustering of Mg within the HA lattice is likely to occur. Such structural characterizations of Mg environments in apatites will favour a better understanding of the biological role of this cation.

Severe acute respiratory syndrome (SARS) in Hong Kong: patients' experiences.

BACKGROUND: This past year there was an outbreak of Severe Acute Respiratory Syndrome (SARS) in Hong Kong. During that time we investigated the clinical features, treatment, and nursing care of 36 patients and reported on 12 of these patients' perceptions of their illness experience. PURPOSE: The purpose of this article is to describe the clinical features, treatment, nursing care and perceptions of the illness experience of patients with SARS in Hong Kong in order to better inform nurses caring for patients with this highly contagious and potentially lethal disease. METHOD: We abstracted data from the medical and nursing records on the clinical features, treatment and nursing care of 36 patients (21 women, 15 men) in whom SARS was diagnosed and who were admitted to the Queen Mary Hospital in Hong Kong between March 15 and April 15, 2003. A review of the hospital's policy and procedures on infection control was also undertaken. Semi-structured interviews were conducted with 12 of the patients to elicit their perceptions of the illness experience. FINDINGS: The most common symptoms were cough (83%), dyspnea (80.6%), malaise (69.4%) and fever (61%). Less common symptoms included headache (38.9%), diarrhea (38.9%), dizziness (30.6%), myalgia (25%), chills (19.4%), nausea and vomiting (19.4%) and rigor (the occurrence of a sensation of hot-and-cold and shivering in addition to teeth chattering and bed shaking) (8.3%). All 36 patients received a combination of corticosteroids and ribavirin. The patients were at risk of drug-related adverse reactions and deterioration of respiratory function, and nursing vigilance was required. CONCLUSION: Nursing patients with SARS was challenging as the disease was highly contagious and potentially lethal, and not much was known about this disease. In addition to the use of frontline treatment, infection control and sensitivity to individual responses to sudden and catastrophic illness were required to support these patients. From this outbreak of SARS, we have learned the importance of infection control in containing and controlling the disease. Other lessons included the need to strengthen the surge capacity in our hospitals and support health care workers during the crisis.