Immunity from attack protection

Metals with protective oxide layers are not immune from attack, especially stainless steels and copper alloys, which may suffer aggressively from crevice corrosion. 

In contrast, most of recently developed pesticides are systemicaUy active and therefore they penetrate the plant cuticle and move through the plant vascular system. Examples of systemic fungicides are benomyl and hexacona-zole. These systemic agents can not only protect a plant from attack but also inhibit or cure established infections. They are not affected by weathering and also confer immunity to all new plant growth. 

The following regions are clearly outHned in F. 2.16 (i) immunity, in which the metal is considered to be immune from corrosion attack (ii) corrosion region, in which the metal corrodes and forms soluble species and (iii) passive region, in which the metal is coated with oxide or hydroxide. By decreasing the potential (cathodic protection), the metal can move from the active corrosion region to the immunity region. Zinc, because of its equiHbrium potential, is used as a sacrificial anode to protect the iron from corrosion. 

Scientists have used water to create almost frictionless lubricated surfaces that stay slippery even under heavy loads. The coating they have developed could shed light on how natural joints are lubricated and provide new ways to protect hip and knee joint implants from friction damage. Over time, the body s immune systan attacks artificial joints. Researchers are now targeting biological interactions rather than trying to solve the problem with new materials. 

However, when administered into the body, the particulate carriers are inevitably exposed to an attack firom the immune system, which protects the body from invasion by foreign products. Thus, injected particles are removed from blood via recognition by phagocytic cells [essentially macrophages located in the mononuclear phagocyte system (MPS), mainly in the liver and spleen]. For example, 50-90% of polystyrene latex particles disappear firom blood within the first five minutes after injection (Ilium et al, 1987). The same fate is observed in the case of particles made of other materials, such as poly(lactic acid) (PLA) (Bazile et al, 1992), polycyanoacrylate (Kreuter et al, 1979), polyacryl starch (Laakso et al, 1986), or albumin (Gottlieb ei a/., 1990). 

Encapsulation. Encapsulation is a technique that allows the cells or tissues from the donor animal to be separated from the human immune system. Usually it does not literally involve a capsule but rather drop>-lets of a viscous gel derived from a nonanimal source such as seaweed. The gel allows the grafted cells to accept nutrients from the human recipient and to diffuse hormones, such as insulin, into the body. At the same time, it protects the grafted cells from attacking antibodies. Encapsulation is not a viable technique for whole organ xenografts. 

Pesticides are chemicals or biological substances used to kill or control pests. They fall into three major classes insecticides, fungicides, and herbicides. Others classes are rodenticides, nematicides, molluscicides, and acaricides. These chemicals can be natural compounds or synthetic ones. Pesticides may also be divided into contact and systemic pesticides. Pesticides that were earlier produced were of the contact type. They do not appreciably penetrate plant tissue, so they are susceptible to the effects of the weather and moreover new plant growth is not protected. Vice versa, most of the recently developed pesticides are systemically active. They move through the plant vascular system and thus they not only can protect a plant from attack but also inhibit or cure established infections. Systemic pesticides are not affected by weathering and also confer immunity to all new plant growth. In 1993, 57% of all the pesticides used in the United States were herbicides, while 23% and 12% were insecticides and fungicides, respectively [1]. 

Immunity region In the conditions of potential and pH of that region a metal is considered to be totally immune from corrosion attack and safe to use. Cathodic protection may be used to bring the potential of a metal closer to that region by forcing a cathodic shift, as shown for aluminum by the domain specified in Fig. 4.14 (or -1.0 to 1.2 V vs. CCSRE). 

The effectors of the mammalian host immune attack against filaria include reactive oxygen intermediates. Filarial nematodes express glutathione peroxidase, thioredoxin peroxidase and superoxide dismutase at their surface - enzymes believed to protect the nematode from this attack (Selkirk et al., 1998). A bacterial catalase gene has been identified that most probably derives from the endosymbiont genome (Henkle-Duhrsen et al., 1998) this enzyme may contribute with other enzymes to the protection of both Wolbachia and its nematode host from oxygen radicals. 

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