Howell Separation

The cytoplasmic organelles may be separated from each other by differential centrifugation or by density gradient centrifugation using sucrose or one of the commercially available alternatives, e.g. Percoll or Metrizamide. Some alternative approaches are considered by Howell et al. (1989). 

Subsequently, Howell improved the separation of heparin from protein by introducing the use of Lloyd s reagent (aluminum silicate) in acetic acid. The final stage then involved the precipitation of the heparin with excess barium hydroxide. Howell claimed that his heparin preparation con-... 

Howell JA. Future of membranes and membrane reactors in green technologies and for water reuse. Desalination 2004 162 1 -11. Kentish SE and Stevens GW. Innovations in separations technology for the recycling and re-use of Uquid waste streams. Chem. Eng. J. 2001 84 149-159. 

Colver and Howell (1980) used the electrostatic EPS (Electric Particulate Suspension) to measure diffusion of spherical copper spheres (74-88 and 125-147 pm) along a copper parallel plate duct having a 1 cm separation distance. The particles were dynamically suspended in the duct by inductive charging... 

The starting material for the present synthesis was the already described alcohol (171), prepared from the Wieland-Miescher ketone (1). It was converted to the ketone (182) by oxidation. Reduction of the ketone (182) yielded the alcohol (183) in 56% yield. Irradiation of a cyclohexane solution of the alcohol with lead tetra-acetate and iodine afforded the expected cyclic ether (184) in 45% yield, which on oxidation yielded the keto-ether (185). The formyl derivative prepared from the keto-ether on subjection to Robinson annelation with 4-diethylaminobutan-2-one methiodide following the procedure of Howell and Taylor [74] afforded the adduct (186). The adduct, when heated with sodium methoxide in methanol produced the tricyclic keto ether (187) whose H N.M.R. spectrum showed it to be a mixture of C-lOa epimers. The completion of the synthesis of pisiferic acid (196) did not require the separation of a and P-epimers and thus the keto ether (187) was used for the next step. 

These laws of friction apply to dry, unlubricated surfaces and to boundary lubricants (very thin solid or nonfluid films separating the surfaces) but not to hydrodynamic lubricants [120], such as fluid layers that separate the moving surfaces (e.g., engine-lubricating oUs). Generally, lipid on the surface of the hair provides a reduction in friction. This is an experimental variable of concern to control (e.g., by careful cleansing of the test surfaces of the fibers or by testing in surfactant solutions, this variable may be controlled). Several theories attempt to explain friction. For discussion of these theories, see the book by Howell et al. [120], Friction in Textiles. 

Jenkins (16) has isolated cyclic monocarboxylic and fatty acids as well as aliphatic esters from petroleum distillates and residues of several crudes. Seifert and Howells (17), through an elaborate extraction and separation scheme, have recovered phenols and carboxylic acids with molecular weights of 300 to 400 from the Midway-Sunset crude. The acidic extracts have been shown to give ultra low (< 10 dyne/cm) interfacial tensions when contacted with an alkali aqueous phase. Phenolic components isolated from the crude were found to diminish the interfacial activity of the acidic fraction. 

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