Physical protective barrier

The viscous mucus layer provides a physical protective barrier for the mucosa trapping, binding, and clearing inspired particles. Approximately 1.5-2 L of mucus is secreted daily and the resultant gel layer varies between 5 and 10 pm in thickness. Mucus is composed of 95% water plus mucin glycoproteins (0.5%-5%), lipids in low proportions, mineral salts (1%), and... 

The disadvantage of physically protective barriers is the rapid and localized corrosion that occurs when the protective layer is scratched or removed locally (Figs. 16.10 and 16.11). Thus, in many cases, the utilization of methods involving continuous electrochemical protection is necessary. 

The side effects inherent to some of these drugs used as lifelong treatment must be taken into account. Also, reduced gastric acidity eliminates a natural physical protective barrier and may cause, with continuous use, bacterial overgrowth [91] and gastroenteral infections [92]. This would be especially problematic for cystic fibrosis patients, who, because of the nature of their disease, are more susceptible to intestinal infections. 

Fire retardancy behavior of PP/PA66 blends compatibilized with PP-g-MAH and modified with untreated and treated nanoclays was studied (Kouini and Serier 2012). It was found that the intercalation, exfoliation of nanoclays of nanocomposites, and the flame retardancy properties were improved significantly. In addition a good balance of impact strength and flame retardancy was obtained for PP/PA66 nanocomposites in the presence of PP-g-MA compatibilizer. The presence of the clay led to an increase in the flammability time. In addition, the treatment made a more pronounced effect. A 23 % increase was observed only when 4 wt% nanoclay was added and a longer flammabiUty time was noticed with treated clay. This was attributed to the stacking of nanoclay which created a physical protective barrier on the surface of the material. Similar behavior has been reported by earlier workers (Kocsis and Apostolov 2004). 

Self-protection means that the reactor plant is capable of preventing damage to physical protective barriers in emergency situations in the event of failure of active safety systems and non-intervention or errors by the plant personnel, by virtue of passive safety systems and inherent safety features based on the action of physical laws of nature which result in selflimitation of the reactor power and temperature. 

Blends of petroleum waxes are commonly used as antiozonants in the rubber industry. Just as 6PPD gives excellent protection against ozone attack of the surface of the rubber under dynamic conditions, waxes will bloom to the surface of the rubber to impart excellent resistance to ozone attack under static conditions. The wax actually exudes (or blooms) to the surface of the rubber article to create a physical protective barrier to protect the rubber surface against ozone attack, which can create cracking of the rubber. 

Rubber is protected against ozone attack by addition of physical and/or chemical antiozonants. Hydrocarbon waxes are the most common type of physical antiozonants, and p-phenylenediamine derivatives are the prevalent chemical antiozonants. Waxes bloom to the rubber surface and form a protective barrier. 

Ozone degradation is a surface phenomenon and hence a physical anti-ozonant must form a protective barrier. A chemical anti-ozonant can be added during polymer fabrication, but again it must diffuse to the surface. It must also provide a defence over the lifetime of the article. 

Hazardous substances may be protected from microbial attack by physical or chemical envelopes. These protective barriers must be destroyed mechanically or chemically to produce fine particles or waste suspensions to increase the surface area for microbial attachment and subsequent biodegradation. Another way to increase the bioavailability of hydrophobic substances is washing of waste or soil by water or a solution of surface-active substances (surfactants). The disadvantage of this technology is the production of secondary hazardous... 

Finally, the particulate barrier did serve to absorb pools of blood ( 150x), adhered to the injured tissue and provide physical abrasion properties that may eventually be a compliment or pretreatment to a wound instead of an environmentally protective barrier dressing. A demonstration of rapid blood absorption by the barrier dressing is shown in Figs. 2.35-2.38. Theoretically, only seconds would be required to absorb fluid from bleeding wounds and form a protective gelatinous layer over the wound. 

Because neither physical nor chemical properties of the immobilizing material in question change over time, monolithization of inner volumes of NS compartments would provide for reliable long-term insulation of immobilized structures from the environmental effects. Monolithized inter-board area would become a reliable protective barrier against radionuclide release to the environment from the inner compartment space and contaminated outer surface of the strong hull. 

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