Surface Morphology Study of Solid Powders Evaluated by Particle Size Distribution and Nitrogen Adsorption

The surface morphology of five tableting excipients including unmilled dicalcium phosphate dihydrate (Di-Tab), microcrystalline cellulose (Avicel PH102), corn starch, croscarmellose sodium (Ac-di-sol), and sodium starch glycolate (Primojel) was studied using laser scattering particle size analysis and nitrogen adsorption surface area analysis. The surface area of particles disregarding porosity was obtained from the particle size distribution and the total area was obtained from the B.E.T. treatment of nitrogen adsorption results. The so-called Surface Irregularity Index (SII) was established to indicate surface roughness due to porosity. The SII value was consistent with the microscopic visualization of a powder sample. Furthermore, the nitrogen adsorption-desorption isotherm hysteresis which showed the evidence of porosity was also consistent with the index. The SII may be an alternative way to characterize the surface morphology of a solid powder.     

Multimethod comparison of similarity in school adjustment of siblings and unrelated children.

Examined similarities among 45 sibling pairs in Grades 2–5 in their social and academic adaptation to the school setting. Measures included teacher ratings and ranking of academic skills, social behavior, and peer acceptance; peer sociometric ratings; and direct observations on the playground with peers and in the classroom with teachers and peers. Comparisons were made with randomly selected, unrelated S pairs matched on sex, grade, and classroom. Significant correlations were found only among sibling pairs on peer ratings of social preference, teachers' judgments of academic competence, popularity, social behavior and school adjustment, positive behavior with peers on the playground, and teachers' disapproving behavior in the classroom. Results underscore the need for more multiagent and multimethod research on sibling concordant–discordant adjustment regardless of theoretical orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An electrophoretic study of the thermal- and reductant-dependent aggregation of the 27 kDa component of ammonia monooxygenase from Nitrosomonas europaea

Standard protocols for sample preparation for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) typically involve the combined use of heat and a reductant to fully disrupt protein-protein interactions and allow for constant ratios of SDS-binding to individual polypeptides. However, 14C-labeled forms of the membrane-bound, active-site-containing 27 kDa polypeptide of ammonia monooxygenase from Nitrosomonas europaea undergo an aggregation reaction when cells or membranes are heated in the presence of SDS-PAGE sample buffer. The aggregate produced after heating at 100 degrees C is a soluble complex which fails to enter the stacking gel in discontinuous SDS-PAGE gels. The extent of the aggregation reaction is dependent on the temperature of sample preparation, and the reaction exhibits first-order kinetics at 65 degrees C and 100 degrees C (rates constants = 0.07 and 0.35 min-1, respectively). The rate of the aggregation reaction is further dependent on the concentration of reductant used in the sample buffer. However, the concentration of SDS does not significantly affect the rate of aggregation. The aggregated form of the 27 kDA polypeptide can be isolated by gel-permeation chromatography in the presence of SDS. The aggregated protein can also be returned to the monomeric state by incubation at high pH in the presence of SDS. The aggregation reaction also occurs with 14C2H2-labeled polypeptides in other species of autotrophic nitrifiers and a methanotrophic bacterium which expresses the particulate form of methane monooxygenase. We conclude that strongly hydrophobic amino acid sequences present in ammonia monooxygenase are responsible for the aggregation phenomenon.     

Cell polarity. The importance of being polar

Cell polarization is often accompanied by cytoskeletal rearrangements. Two signalling proteins, a GTPase and a kinase, are required for both actin and microtubule rearrangements. Are these two systems coupled?     

Monoclonal antibodies to CD44 and their influence on hyaluronan recognition

Antibodies to CD44 have been used to inhibit a variety of processes which include lymphohemopoiesis, lymphocyte migration, and tumor metastasis. Some, but not all, CD44-mediated functions derive from its ability to serve as a receptor for hyaluronan (HA). However, sites on CD44 that interact with either ligands or antibodies are poorly understood. Interspecies rat/mouse CD44 chimeras were used to analyze the specificity of 25 mAbs and to determine that they recognize at least seven epitopes. Amino acid substitutions that resulted in loss of antibody recognition were all located in the region of homology to other cartilage link family proteins. While at least five epitopes were eliminated by single amino acid replacements, multiple residues had to be changed to destroy binding by other antibodies. One antibody was sensitive to changes in any of three separate parts of the molecule and some antibodies to distinct epitopes cross-blocked each other. Certain antibodies had the ability to increase HA binding by lymphocytes but this did not correlate absolutely with antibody specificity and was only partially attributable to CD44 cross-linking. Antibodies that consistently blocked HA recognition were all sensitive to amino acid changes within a short stretch of CD44. Such blocking antibodies interacted with CD44 more strongly than ligand in competition experiments. One large group of antibodies blocked ligand binding, but only with a particular cell line. This detailed analysis adds to our understanding of functional domains within CD44 and requirements for antibodies to influence recognition of one ligand.     

Behaviour of power leads for superconducting magnets

In this paper we have attempted to gather together much of the information required by the designer of dc superconducting magnets. The new aspects of this work are: more information concerning performance of leads operating away from optimum conditions; comparisons of ideal cooling and a more realistic model for gas cooling; properties of gas-cooled leads on loss of coolant.     

Differential Scanning Calorimetry of Aspartame-Mannitol Mixture

Differential scanning calorimetry was used to study both the qualitative and quantitative thermal properties of mixtures of aspartame with both mannitol and granular mannitol. Aspartame was found to be compatible with both forms of mannitol. No aspartame decomposition was observed in the preparation of a fused aspartame-mannitol mixture prepared at 161-165°C. L-(-)-leucine can be recommended as soluble lubricant for formulations containing aspartame and mannitol.     

Water Based Silicone Elastomer Controlled Release Tablet Film Coating III - Drug Release Mechanisms

The release of potassium chloride from polyethylene glycol-silicone elastomer coated tablets was achieved by the diffusion through water-filled pores formed in the hydrated coating and the osmotic pumping generated by the saturated salt solution. The relative contribution of these two mechanisms to the overall drug release rate was shown to be a function of the polyethylene glycol loading in the coating. As the polyethylene glycol loading level increased, the transpore diffusion became the predominant release mechanism. The capability of the polyethylene glycol-silicone elastomer coatings to provide controlled release for therapeutic agents of different water solubilities and dose levels was also demonstrated. Both the rate and extent of release of the active ingredients could be altered by the type of diluent used in the tablet matrix