Some angular properties of magnesia and their relevance to material handling

Fine sand particles enable antlions to build pitfall traps with advanced three-dimensional geometry

Pit-building antlion larvae are predators that construct pitfall traps in fine sand. We used three-dimensional laser scanning and geometric morphometrics to reveal the shape of antlion pits of two antlion species, analysed the particle size composition of sands from the different natural habitats, and measured the slope angles of the pits of the two species. In most antlions, the pits are structured as a simple inverted cone, as in Myrmeleon hyalinus, studied here. The other antlion studied, Cueta lineosa, constructs a unique pit composed of two inverted truncated cones inserted into one another, which feature substantially steeper walls than the pits of any other antlion studied to date. Pit stability depends on the slope inclination, which oscillates between the maximum angle of stability and the angle of repose. The angles in C. linosa substrates were larger than those in M. hyalinus substrates. One reason for the steeper walls is the greater proportion of fine sand in the natural sand inhabited by C. lineosa However, video-recording revealed that both the natural sand of C. lineosa and the finest sand tested had a higher maximum angle of stability than any of the other substrates studied here. Furthermore, experiments with pits built in different substrates revealed that the shape of the pit is variable and depends on the structure of the sand. Myrmeleonhyalinus displayed a more flexible pit construction behaviour than C. lineosa The present demonstration of such differences in pit characteristics contributes to understanding how these two species co-exist in the same habitat.

Physico-mechanical characterization of policosanol, a novel hypocholesterolemic drug

As part of the formulation studies of policosanol, a new hypocholesterolemic drug, a physico-mechanical characterization was developed. Thermal analysis, using differential scanning calorimetry was used to evaluate the purity of policosanol from batch to batch and, also, the particle size distribution. The degree of wettability of policosanol was studied by measuring the contact angle and solubility in different solvents. The compressibility and cohesion of particles were evaluated using a profile of compression forces, ranging between 6.5 kN and 39.0 kN. Also, other properties such as flow properties, true density, and tapped and bulk density were measured. The industrial batches of policosanol that were studied show an adequate purity and a uniform distribution of the particle sizes. Policosanol shows good flow properties, compressibility, and cohesion as well as a low solubility in the majority of the solvents used in the pharmaceutical industry, and its solubility in water or in aqueous solutions was, mainly, null. The wettability of policosanol in the different solvents shows the following order: methylene chloride > ethanol > acetone >> water.

The formulation of powder inhalation systems containing a high mass of nedocromil sodium trihydrate

Nedocromil sodium trihydrate is not amenable to conventional methods of dry powder inhaler formulation, including the preparation of coarse carrier systems and aggregation of the pure drug powder. It is considered that the in vitro aerosol performance of such systems is governed by the cohesive drug-drug interactions. Therefore, alternative powder formulation strategies (novel to nedocromil sodium) were developed. By decreasing the particle size of the lactose carrier, the deaggregation and subsequent fine particle drug deposition were significantly improved. Further improvements were made by selecting and then optimizing high-shear mixing procedures. It was concluded, based on these findings and supportive microscopic studies (low-temperature and environmental scanning electron microscopy together with energy-dispersive X-ray analysis), that the FPL are producing their functional effects by intercalating within the drug self-agglomerates and physically disrupting the cohesive drug-drug interactions. The use of a smaller-sized lactose fraction in conjunction with a blending procedure capable of optimally disrupting the drug self-agglomerates allowed maximal intercalation of the excipient material within the drug self-agglomerates. The adhesive drug-FPL interactions are considered to be weak compared with the cohesive drug-drug particle interactions, cohesive interactions that would normally govern the aerosol performance of powder systems containing a high mass of nedocromil sodium trihydrate.

Flow rates and repose angles of wet-processed granulations

The equation of McDougall and Evans was found not to apply to granulations. The functional relationships among volumetric powder flow rates, angles of repose, and particle size were demonstrated to exhibit maxima (rather than minima) in five common pharmaceutical granulations produced by wet processing. The angular behavior of granules (such as the experienced range of angles) is explained via supported stacking geometries, and the shallow maxima in the angle of repose versus granule diameter was derived from this model.