Determination of phase stability of elemental boron.

Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or ß) is stable at ambient conditions. Through experiment, we quantify the relative stability of α-boron and ß-boron as a function of temperature. The ground-state energies of α-boron and ß-boron are nearly identical. For all temperatures up to 2000 K, the complicated ß-boron structure is more stable than the simpler α-boron structure at ambient pressure. Below 1000 K, ß-boron is entropically stabilized with respect to α-boron owing to its partially occupied sites, whereas at higher temperatures ß-boron is enthalpically stabilized with respect to α-boron. We show that α-boron only becomes stable on application of pressure.

Doxorubicin-loaded polyphosphate glass microspheres for transarterial chemoembolization.

The standard of care for intermediate stage hepatocellular carcinoma is transarterial chemoembolization (TACE). Drug-eluting bead TACE (DEB-TACE) has emerged as a leading form of TACE, as it uses highly calibrated microspheres to deliver consistent embolization and controlled drug release to the tumor microenvironment. We report here on doxorubicin (DOX)-loaded polyphosphate glass microspheres (PGM) as a novel resorbable, radiopaque, preloaded DEB-TACE platform. Coacervate composed of polyphosphate chains complexed with Ba2+ , Ca2+ , and Cu2+ can be loaded with DOX prior to PGM synthesis, with PGM production achieved using a water-in-oil emulsion technique at room temperature yielding highly spherical particles in clinically relevant size fractions. In vitro, DOX release was found to be linear, pH dependent, and in accordance with Type II non-Fickian transport. PGM degradation was characterized by an initial burst release of degradation products over 7 days, followed by a plateau in mass loss at approximately 75% over a period of several weeks. in vitro studies indicate that PGM degradation products, namely Cu2+ , are cytotoxic and may interact with eluted DOX to impair its pharmacological activity. With additional compositional considerations, this approach may prove promising for DEB-TACE applications.

Investigation of factors affecting crystallization of cyclopentane clathrate hydrate.

We report the results of systematic investigations of the influence of thermal history and other factors on crystallization of a model clathrate hydrate (cyclopentane hydrate) studied as water-in-oil and oil-in-water emulsions to remove the nucleation influence of substrates other than ice and hydrates. Hydrate and ice seem to form simultaneously under the conditions of these experiments, with ice forming preferentially. Thermal treatment, melting the ice, and leaving only the hydrate, promotes further hydrate formation. Not all the hydrate formed can be accounted for by the recrystallization of water freed by melting ice.