High absorption rate

Owing to the high absorption rate of hexachlorophene through damaged skin and the risk of fatal intoxication, the use of hexachlorophene in the treatment of burns or on otherwise excoriated skin is strongly contraindicated. 

As the suppository base is heated before moulding, certain effects can be noted which are unique to this type of medication. Testosterone dissolves when hot in the semisynthetic excipient Witepsol H, to give, on cooling, crystals of about 2-3 /rm in diameter. After dissolution in theobroma oil, the dmg does not crystallise on cooling but remains dissolved as a solid solution. In the former case, high absorption rates are obtained, while in the latter poor absorption is achieved. Because of the effect of particle size on the viscosity of suspensions (see section 7.4.4) it is preferable to avoid the incorporation of ultra-fine crystals as the resultant melt of suspension has a higher viscosity than those produced from coarser crystals. 

Swelling can cause softening of the polymer, introduce high stresses, and cause failure of the bond on lined components. If the polymer has a high absorption rate, permeation will probably take place. An approximation of the expected permeation and/or absorption of a polymer can be based on the absorption of water. This data is usually available. Table 1.8 provides the water absorption rates for the more common polymers. Table 1.9 gives the absorption rates of various liquids by FEP, and Table 1.10 provides the absorption rates of representative liquids by PFA. 

A recent innovation imder study in the area of radiation therapy is boron—neutron capture therapy for brain tumor. This form of therapy uses an inactive tracer containing boron, an element with a high absorption rate of neutron radiation. When the radiopharmaceutical has accumulated in the tumor, the patient is exposed to neutron radiation, which is absorbed by boron. The energy of secondary low-range a-radiation, which is formed in the boron—neutron reactions, is then absorbed by the tumor cells that are to be destroyed. 

Gas phase dispersion Important at high absorption rates and high conversion of gaseous reactant, respectively. Very important, comparable with one-phase reactors... 

Boron carbide has very high structural stability under irradiation [37]. However, when used as a neutron absorber, very high absorption rates are obtained (the volume density of neutron captures by °B is most often called bumup) in SFR, up to 10 He/cm is produced, leading to drastic modifications of the microstructure and of the composition and high energy release (about 100 W/cm ). 

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