Immune virtual

Vaccination and immunization programmes seldom confer 100% protection against the target disease. More commonly the degree of protection is c. 60-95%. In such instances, while individuals receiving treatment will have a high probability of becoming immune, virtually all members of a community must be treated in order to reduce the actual proportion of susceptible individuals to below the threshold for epidemic spread of the dis-... 

Virtually all metallurgies can be attacked by corrosive bacteria. Cases of titanium corrosion are, however, rare. Copper alloys are not immune to bacterial attack however, corrosion morphologies on copper alloys are not well defined. Tubercles on carbon steel and common cast irons sometimes contain sulfate-reducing and acid-producing bacteria. Potentially corrosive anaerobic bacteria are often present beneath... 

Admiralty brass (70% Cu, 29% Zn, 1% Sn, 0.05% As or Sb) and arsenical aliuninum brass (76% Cu, 22% Zn, 2% Al, 0.05% As) are resistant to dezincification in most cooling water environments. In the recent past, heat exchangers have virtually always been tubed with inhibited grades of brass. Brasses containing 15% or less zinc are almost immune to dezincification. Dezincification is common in uninhibited brasses containing more than 20% zinc. Inhibiting elements include arsenic, antimony, and phosphorus. Without inhibiting elements. 

Zinc brasses containing phosphorus, antimony, and/or arsenic dezinc-ify much less readily than brasses free of these elements. Brasses containing less than 15% zinc are virtually immune to attack, and those containing more than 32% zinc are readily dealloyed. 

Complexes o/M". The absence of any other oxidation state of comparable stability for nickel implies that compounds of Ni" are largely immune to normal redox reactions. Ni" forms salts with virtually every anion and has an extensive aqueous chemistry based on the green [Ni(H20)6] + ion which is always present in the absence of strongly complexing ligands. 

In practice, by far the most common case of stress corrosion is that occurring when austenitic stainless steels are simultaneously exposed to tensile stresses and hot, aqueous, aerated, chloride-containing environments. In this case the major variable is alloy composition and structure virtually all austenitic stainless steels are more or less susceptible to stress-corrosion cracking in these environments, while ferritic and ferritic/austenitic stainless steels are highly resistant or immune. 

Plain chromium, ferritic steels are much more resistant and for a time were considered virtually immune to stress-corrosion cracking. It is now known that failure can be caused, especially if the steels contain addition of copper, cobalt or nickel. Even so, resistance is superior to that of the standard austenitics, and ferritics are used where stress-corrosion cracking of the austenitic grades could be a possibility . 

Tantalum has a high resistance to general outdoor atmospheres. Tantalum and the Ta-lOW alloy are virtually immune to sea water at ambient conditions and tantalum is only tarnished in oxygenated sea water at 26°C. 

Some duplex alloys have even better pitting resistance than type 316 and should be considered in severely pitting media. Titanium is virtually immune to chloride pitting and cupro-nickel alloys are used for condensers where sea-water is the coolant high pitting resistance in this duty is claimed for Cu-25Ni-20Cr-4-5Mo. 

The proof of protection is more difficult to establish in this case for two reasons. First, the object is to restore passivity to the rebar and not to render it virtually immune to corrosion. Second, it is difficult to measure the true electrode potential of rebars under these conditions. This is because the cathodic-protection current flowing through the concrete produces a voltage error in the measurements made (see below). For this reason it has been found convenient to use a potential decay technique to assess protection rather than a direct potential measurement. Thus a 100 mV decay of polarisation in 4 h once current has been interrupted has been adopted as the criterion for adequate protection. It will be seen that this proposal does not differ substantially from the decay criterion included in Table 10.3 and recommended by NACE for assessing the full protection of steel in other environments. Of course, in this case the cathodic polarisation is intended to inhibit pit growth and restore passivity, not to establish effective immunity. 

Antibodies are highly specific, binding only to a restricted part of a given antigen known as an epitope. Given the billions of antibody specificities that may be produced by the immune system, an antibody that recognizes an epitope on virtually any molecule may be produced. It is this property that makes antibodies immensely powerful tools for experimental, diagnostic and therapeutic procedures. 

Compared with tar, which has a relatively short lifetime in the marine environment, the residence times of plastic, glass and non-corrodible metallic debris are indefinite. Most plastic articles are fabricated from polyethylene, polystyrene or polyvinyl chloride. With molecular weights ranging to over 500,000, the only chemical reactivity of these polymers is derived from any residual unsaturation and, therefore, they are essentially inert chemically and photochemically. Further, since indigenous microflora lack the enzyme systems necessary to degrade most of these polymers, articles manufactured from them are highly resistant or virtually immune to biodegradation. That is, the properties that render plastics so durable... 

Immunoassays are based on the ability of the immune system to produce a virtually unlimited variety of antibodies each with a high affinity for foreign compounds (immunogens like viruses, bacteria, proteins, and haptens). Analytically, this phenomenon can be exploited by detection of this immunoreaction using labeled antibodies or antigens (i.e., compounds that can be bound by antibodies). The equilibrium between antibody (Ab), antigen (Ag), and immune complex (Ab-Ag) may be expressed as ... 

There exists direct evidence that the immune system mounts an immune response against most cancer types. Virtually all transformed cells express (a) novel surface antigens not expressed by normal cells or (b) express, at greatly elevated levels, certain antigens present normally on the cell at extremely low levels. These normal expression levels may be so low that they have gone unnoticed by immune surveillance (and thus have not induced immunological tolerance). 

Virtually all serotypes of S. pneumoniae exhibiting intermediate or complete resistance to penicillin are found in the current 23 serotype pneumococcal vaccine. A heptavalent conjugate vaccine is available for use in infants between 2 months and 9 years of age. Current recommendations are for all healthy infants younger than 2 years of age to be immunized with the heptavalent vaccine at 2, 4, 6, and 12 to 15 months. 

Host resistance to disease has been used as an effective measure of the impact of environmental toxicants on immune function. To date, for virtually every agent examined,... 

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