Paramagnetic spherical nanoparticles by the self-assembly of persistent trityl radicals.

Spherical nanoparticles and fibres observable by cryo-electron microscopy are spontaneously formed by the Finland trityl radical at concentrations above 15 mM. These species represent a new class of paramagnetic, metal-free, nanoscale supramolecular materials. Self-association was observed under a variety of experimental conditions, including aqueous solution at room temperature, low temperature frozen glasses and the gas phase. Oligomers formed by at least 5 Finland radicals were detected by ion-mobility mass spectrometry. Magnetic susceptibility data as well as low temperature EPR spectra show coupling between electronic spins in the self-assembled species. Quantum chemical calculations show stacking along the C3 symmetry axis. Nanoparticle formation requires additional lateral packing that can be provided by hydrogen bonding involving the triangular array of carboxylic acid groups leading to the assembly of geodesic spheres.

Self-assembled trityl radical capsules--implications for dynamic nuclear polarization.

A new class of guest-induced, bi-radical self-assembled organic capsules is reported. They are formed by the inclusion of a tetramethylammonium (TMA) cation between two monomers of the stable trityl radical OX63. OX63 is extensively used in dissolution dynamic nuclear polarization (DNP) where it leads to NMR sensitivity enhancements of several orders of magnitude. The supramolecular properties of OX63 have a strong impact on its DNP properties. An especially relevant case is the polarization of choline-containing metabolites, where complex formation between choline and OX63 results in faster relaxation.

Periosteal ganglion in a child.

A case of periosteal ganglion in a 10-year-old boy is reported. The diagnosis of periosteal ganglion was made on roentgenographic and MR appearance and histologic evidence. The patient was successfully treated by excision. The follow-up examination showed no recurrence. Periosteal ganglia must be considered a cause of expanding cortical erosions. This lesion may mimic other peripheral expanding lesions.

Lesion/fat intensity ratio in MR characterization of hepatic masses.

On T2-weighted spin echo images, lesion/liver intensity ratios can be used to accurately distinguish hepatic cavernous hemangioma from malignant lesions. However, since patients with focal liver lesions may present diffuse liver disease, this relationship can be inaccurate. We studied 91 hepatic lesions to compare the value of lesion/liver and lesion/fat ratios in the differential diagnosis of liver lesions. In doubtful cases the use of lesion/fat intensity ratio can be used to improve accuracy in the diagnosis of liver lesions. The combination of both ratios into a single diagnostic index gave a correct classification of malignant versus hemangioma in 92.3% of the cases.

High density barium sulphate as an MRI oral contrast.

High density barium sulphate suspension was investigated as an oral contrast on MRI. On 30 consecutive subjects, the stomach (in all cases) and the two first portions of the duodenum (in 21 cases) were filled with the suspension. This oral contrast behaved as a negative contrast, being hypointense on all pulse sequences (spin-echo T1-weighted, spin-echo T2-weighted and STIR). This characteristic is probably due to the low proton density of the suspension (260 +/- 40). Since barium sulphate is inexpensive, harmless and available on all radiologic departments, it is recommendable in MRI studies of the liver and head of the pancreas.

[Relation between the carcinogenic activity of conjugated polycyclic hydrocarbons and the form of their localized molecular orbitals]. / Relación entre la actividad cancerígena de los hidrocarburos policíclicos conjugados y la forma de sus orbitales moleculares localizados.

The carcinogenic activity of some compounds is linked to the electronic structure of their molecules. The authors calculate the localized molecular orbitals (LMO) by means of a topologic method they have developed, based in the electronic distribution of a single molecular region, that coincides or is next to the K region, instead of having to consider the two classical regions (K and L).