P-speck

Schlapfer E, Fischer M, Ott P, Speck RF. Anti-HIV-1 activity of leflunomide a comparison with mycophenolic acid and hydroxyurea. AIDS 2003 17(ll) 1613-20. 

P. Speck, F. Escher, and J. Sohns, Effect of salt pretreatment on quality and storage stability of air-dried carrots, LWT, 70 308 (1977). 

Discolored specks are a common problem in extrusion and molding. This problem is similar to another common defect, which is the problem of gels. Like gels, discolored specks are formed not only in extrusion and molding at the processor but also in polymerization at the resin producer. As a result, in order to get a handle on the problem, we need to know how many specks are in the incoming raw material. We will distinguish between a speck formed in polymerization and located inside the pellet (P-speck) and a speck formed in extrusion (E-speck). 

If we have one pellet with a discolored speck for every N pellets, we can determine the average incidence of specks in the extruded product. If the cross-sectional area of the extruded product is and the volume of the pellet or powder particle is Vp, the average length over which a P-speck will occur in the extruded product is ... 

The volume of the pellet is 20 mm We will consider a plastic raw material that contains one pellet with a discolored P-speck for every 10,000 pellets this corresponds to 100 ppm. With this input data, we find the average length over which a P-speck will occur is 5806 mm or 5.8 m. If we generate specks in the extrusion process, the average length over which a speck occurs in the extruded product will be less than 5.8 meter. 

If we cannot tolerate one speck every 5.8 meter there is only one option reducing the number of P-specks in the raw material. Since resin producers can scan millions of pellets for specks, it is also possible to remove pellets with specks from the pellet stream. In other words, the processor can specify the ppm level of pellets with specks that can be tolerated by the processor. 

Discolored specks are ubiquitous in the plastic extrusion industry. Controlling specks starts with quantifying P-specks in the incoming raw material. Once we can control P-specks to an acceptable level, we can address E-specks. Important factors that affect E-specks have been identified with one factor, screw wear, discussed in detail. 

Slos, P., Speck, D., Accart, N., Kolbe, H.V., Schubnel, D., Bouchon, B., Bischoff, R., and Kieny, M.P., 1994, Recombinant Cholera Toxin B Subunit in E. Coli High-level Secretion, Purification, and Characterization, In Protein Expression Purif, 5, 518-26... 

Fraker, P.J., and Speck Jr., J.C. (1978) Protein and cell membrane iodinations with a sparingly soluble chlo-roamide, l,3,4,6-tetrachloro-3a,6a-diphenylglycouril. Biochem. Biophys. Res. Comm. 80, 849-857. 

P.Y.108 is applied in various types of industrial finishes, especially in original automotive (O.E.M) and in automotive refinishes. It is also recommended for metallic finishes, although it is much less weatherfast in such systems. The pigment tends to seed, i.e., it forms specks upon storage. The mechanism behind this phenomenon remains to be elucidated. Besides, P.Y.108 also lends color to emulsion paints, in which it is durable enough to satisfy the requirements for exterior paints based on synthetic resin dispersions. It is also fast to acids, alkali, and plaster. 

Haworth, S., Lawlor, T., Mortelmans, K., Speck, W. Zeiger, E. (1983) Salmonella mutagenicity test results for 250 chemicals. Environ. Mutag., 5 (Suppl. 1), 3-142 Kilpatrick, S.J. Laros, R.K. (1999) Maternal hematologic disorders. In Creasy, R.K. Resnik, R., q6.. Maternal-fetal Medicine, Philadelphia, W.B. Saunders, pp. 935-963 Lewis, R.J., Jr (1993) Hawley s Condensed Chemical Dictionary, 12th Ed., New York, Van Nostrand Reinhold, p. 55... 

Melnick, R.L. Tomaszewski, K.E. (1990) Triethanolamine. In Buhler, D.R. Reed, D.J., eds, Ethel Browning s Toxicity and Metabolism ofIndustrial Solvents, Vol. II, Nitrogen and Phosphorus Solvents, Amsterdam, Elsevier, pp. 441-450 Morin, R.J. Lim, C.T (1970) Inhibition in vitro of incorporation of [ P]-phosphate into rabbit and human endometrial phospholipids. J. reprod. Fert., 23, 456-462 Mortelmans, K., Haworth, S., Lawlor, T., Speck, W., Tainer, B. Zeiger, E. (1986) Salmonella mutagenicity tests II. Results from the testing of 270 chemicals. Environ, mol. Mutag., 8 (Suppl. 7), 1-119... 

Porphyrin quinones serve as biomimetic models for fundamental studies on photo-induced ET. Most studies have been performed with the well-known porphyrin p-quinones and the isomeric porphyrin o-quinones have been mostly neglected due to their higher chemical reactivity but in fact they should be better electron acceptors. Speck et al. synthesized several porphyrin o-quinones and have shown that a facile and simple variation of AGEt can be achieved by using in situ formed semiquinones for metal chelation230. 

Weinmann H-J, Gries H, Speck U (1989) In Runge VM (ed) Enhanced Magnetic Resonance Imaging The C.V. Mosby Company StLouis Baltimore Toronto p. 74... 

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