Stability physical

Stability considerations Chemical stability Physical stability Microbiological stability Bioavailability stability... 

Work conducted by J. Rubin at PicArsn and reported in Ref 18 indicates that there is no significant difference in sensitivity between the 60/40/1 RDX/TNT/wax mix (Compn B) and the 60/40 mix without the wax when the expls are tested in the powdered form in standard laboratory tests. These studies also indicate no difference in stability, physical or other expl characteristics or casting properties. Subsequent results of work also reported by Rubin (Ref 24), however, indicated that when the two compns are tested for sensitivity in the cast form, the unwaxed expl is more sensitive than the waxed compn. Tests conducted which show this difference in sensitivity are the large scale Bureau... 

Physical Stability. Physical stability depends primarily on the purity of the enzyme. Impurities remaining from the fermentation broth may precipitate or form a hazy solution. Unwanted sedimentation is often related to Ca2+ or acidic polysaccharides. The solubility of some enzymes can be increased by optimizing the ionic strength or changing the dielectric constant of the solution by adding low molecular-weight polyols. 

Similar to the importance of mechanical stability, physical properties such as surface area, pore size, and pore size distribution, metal dispersion, and surface acidity are important parameters, which the catalytic chemist or engineer considers when developing a catalytic system. The physical properties are optimized to fit the catalytic application. Measurement of these properties, while not all are fully standardized, have been widely published for specific catalytic systems. The most complete review of these procedures with examples for specific catalytic systems and references have been published (7-8). ... 

The diffusion rate determines how e ily can be a stabilizer physically lost by extraction or volatilization. Changes in the mobility of stabilizers or of species with which a stabilizer interacts (e.g. RO2) are reflected in the finally observed stabilization effect [27]. 

S.H. White and W.C. Wimley. 1999. Membrane protein folding and stability Physical principles Annu. Rev. Biophys. Biomol. Struct. 28 319-365. (PubMed)... 

For pharmaceutical materials moisture is known to affect a wide range of properties such as powder flow compactibility and stability (physical chemical and microbiological) (8 46-53). The interaction between moisture and a solid is complex and can occur in a variety of ways. For example water can be stoichiometrically incorporated into a solid s crystal structure in the form of a hydrate (pseudo-hydrate) as discussed previously in this section. In addition moisture can have non-stroichiometrical i.e., nonspecific interactions with a solid by adsorbing on the surface or being absorbed into the material and acting as a plasticizer. These non-specific interactions are more common in amorphous or semi crystalline materials and are the subject of this section. 

Precision is worse with systematic errors Sample stability (physical or chemical) is occasionally a problem when sequential procession is used... 

Physical Stability Physical stability can refer to molecular level changes, such as polymorphic changes, or macroscopic changes, such as dissolution rate or... 

Stability testing Results of stability, physical as well as chemical tests, methodology used (WHO guidelines or ICH guidelines), validation ... 

Lallemand, P. Luo, L.-S. 2003 Theory of the lattice Boltzmann method dispersion, dissipation, isotropy, Galilean invariance, and stability. Physical Review E 68,036706. 

Kubsch, J.E., J.S. Rieck and N.D. Spencer, 1991, Cerium oxide stabilization physical property and three-way activity considerations, in Catalysis and Automotive Pollution Control II, ed. A. Crucg (Elsevier, Amsterdam) pp. 125-138. 

The second main point in the chapter is the stabilization of a radical center by the presence of alkyl groups attached to the radical carbon. So, ZerZ-butyl radical is more stable than isopropyl, which is better than ethyl methyl radical is the least stable. Hyperconjugation is one concept often used to explain this stabilization. Physically, and electrostatically, the radical carbon can be viewed as somewhat electron deficient (7 valence electrons instead of an octet). Hyperconjugation provides a means for bonds in neighboring alkyl groups to lend" a little electron density to the radical center, thereby making it feel a little less electron-poor. In doing so, the... 

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