A material-sparing simplified buoyancy method for determining the true density of solids.

True density is an important physical property of powdered materials, especially in the context of powder compaction. Currently available methods for true density determination either require a significant amount of materials or are laborious. Hence, a material-sparing and efficient method for true density determination is of value. In this work, we detail a simplified buoyancy-based method capable of fast determination of true density with accuracy comparable to helium pycnometry. This miniaturized method only uses a few milligrams of a powder with data collection process expedited by centrifugation in a laboratory centrifuge. This method can be easily adapted in a laboratory since determination of true density only requires a balance, a micropipette, a laboratory centrifuge, and standard stock liquids of low and high densities. Hence, it is a useful addition to the materials characterization tool kit critical for pharmaceutical formulation development.

Bulk phase biochemistry of PIF1 and RecQ4 family helicases.

DNA helicases are involved in nearly all facets of genome integrity, and in humans, mutations in helicase-encoding genes are often linked to diseases of genomic instability. Two highly studied and evolutionarily conserved helicase families are the PIF1 and RecQ helicases. Enzymes in these families have known roles in DNA replication, recombination, and repair, as well as telomere maintenance, DNA recombination, and transcription. Although genetics, structural biology, and a variety of other techniques have been used to study these helicases, ensemble analyses of their basic biochemical activities such as DNA binding, ATP hydrolysis, and DNA unwinding have made significant contributions to our understanding of their physiological roles. Here, we present general methods to generate recombinant proteins from both helicase families, as well as standard biochemical assays to investigate their activities on DNA.

Isolation of wild yeasts from Olympic National Park and Moniliella megachiliensis ONP131 physiological characterization for beer fermentation.

Thousands of yeasts have the potential for industrial application, though many were initially considered contaminants in the beer industry. However, these organisms are currently considered important components in beers because they contribute new flavors. Non-Saccharomyces wild yeasts can be important tools in the development of new products, and the objective of this work was to obtain and characterize novel yeast isolates for their ability to produce beer. Wild yeasts were isolated from environmental samples from Olympic National Park and analyzed for their ability to ferment malt extract medium and beer wort. Six different strains were isolated, of which Moniliella megachiliensis ONP131 displayed the highest levels of attenuation during fermentations. We found that M. megachiliensis could be propagated in common yeast media, tolerated incubation temperatures of 37 °C and a pH of 2.5, and was able to grow in media containing maltose as the sole carbon source. Yeast cultivation was considerably impacted (p < 0.05) by lactic acid, ethanol, and high concentrations of maltose, but ONP131 was tolerant to high salinity and hop acid concentrations. This is one of the first physiological characterizations of M. megachiliensis, which has potential for the production of beer and other fermented beverages.

Proportionality between powder cohesion and unconfined yield strength from shear cell testing.

From an analysis of the geometry of the yield locus and the Mohr's circle for determining unconfined yield strength (f c) in shear cell testing, it has been shown that powder cohesion is proportional to f c, where the proportionality constant is a function of angle of linearized yield locus, (1-sinθ)/(2cosθ). While both parameters are routinely included in shear cell data, only one parameter is needed to characterize flow properties of a new powder.