Protective capacity

Reactions With Metals. AH metals react to some extent with the halogen fluorides, although several react only superficiaHy to form an adherent fluoride film of low permeabHity that serves as protection against further reaction. This protective capacity is lost at elevated temperatures, however. Hence, each metal has a temperature above which it continues to react. Mild steel reacts rapidly above 250°C. Copper and nickel lose the abHity to resist reaction above 400 and 750°C, respectively. 

In neutral and alkaline environments, the magnesium hydroxide product can form a surface film which offers considerable protection to the pure metal or its common alloys. Electron diffraction studies of the film formed ia humid air iadicate that it is amorphous, with the oxidation rate reported to be less than 0.01 /rni/yr. If the humidity level is sufficiently high, so that condensation occurs on the surface of the sample, the amorphous film is found to contain at least some crystalline magnesium hydroxide (bmcite). The crystalline magnesium hydroxide is also protective ia deionized water at room temperature. The aeration of the water has Httie or no measurable effect on the corrosion resistance. However, as the water temperature is iacreased to 100°C, the protective capacity of the film begias to erode, particularly ia the presence of certain cathodic contaminants ia either the metal or the water (121,122). 

Zinc is often used as a protective coating over iron to form galvanized iron. In industrial settings exposed to SOj and humidity, this zinc coating is subject to sufficient corrosion to destroy its protective capacity. Haynie and Upham (5) used their results from a zinc corrosion study to predict the useful life of a zinc-coated galvanized sheet in different environmental settings. Table 9-2 shows the predicted useful life as a function of SO concentration. 

Ramaswamy, K., Goodman, R.E. and Bell, R.G. (1994) Cytokine profile of protective anti-Trichinella spiralis CD4 0x22- and non-protective CD4+ 0x22+ thoracic duct cells in rats secretion of IL-4 alone does not determine protective capacity. Parasite Immunology 16, 435-445. 

To provide expert advice, and to assist a State Party, when requested, in identifying how its programmes for the development and improvement of a protective capacity against chemical weapons can be implemented3 ... 

Yorty, J.L. and Bonneau, R.H., Impact of maternal stress on the transmammary transfer and protective capacity of herpes simplex virus-specific immunity, Amer. J. Physiol. Reg. Integrat. Comp. Physiol., 287, R1316, 2004. 

CTL induction experiments consistently demonstrate that IRIV indeed enhance induction of HLA class I-restricted CTL specific for IMsg-ee and Melan-A/Mart-127-35 epitopes. CTL induction in presence of irradiated or nonirradiated CD4+ cells showed that IRIV CTL adjuvance requires CD4+ T-cell activation. Remarkably, IRIV CTL adjuvance observed in our in vitro studies is solely due to IRIV immunogenicity and independent of peptide delivery and protection capacities, as peptides were not encapsulated in nor attached to IRIV. Further studies are warranted to clarify whether and to what extent delivery, protection, and immunogenic capacities of IRIV synergize in CTL adjuvance. The fact that IRIV adjuvance was observed in relation to the tumor-associated epitope Melan-A/Mart-127-35 encourages further evaluation of IRIV as potential adjuvants in cancer... 

Percutaneous drug absorption can present special problems in newborns, especially in preterm infants. While the skin of a newborn term infant may have the same protective capacity as the skin of an adult, a preterm infant will not have this protective barrier until after 2 to 3 weeks of life. Excessive percutaneous absorption has caused significant toxicity to preterm babies. Absorption of hexachlorophene soap used to bathe newborns has resulted in brain damage and death. Aniline dyes on hospital linen have caused cyanosis secondary to methemoglobinemia, and EMLA (lidocaine/prilocaine) cream may cause methemoglobinemia when administered to infants less than 3 months of age. 

The durability of concrete is the ability of the material to maintain its structural integrity, protective capacity, and aesthetic qualities over a prolonged period of time. It is important that the benefits conferred to concrete in the plastic and early hardened state by water-reducing admixtures are not negated by any adverse effect on the long term durability. 

The formation of the passive layer at the concrete/reinforcement interface referred to earlier (Section 1.4) is due to the alkaline nature of the concrete. The alkalinity is due to calcium, sodium and potassium hydroxides which, over a period of time, react with atmospheric carbon dioxide to form carbonates. This reduction in alkalinity in reflected in a diminished protective capacity towards the steel reinforcement. 

The oxide film which helped create the cathodic areas in the first place may be destroyed by reductive dissolution, at least in the case of iron, because of the excess of electrons present at cathodic sites. This is possible for iron because of the accessibility of the iron (II) oxidation state. The extreme insolubility (and hence protective capacity) of the oxide film derives from its iron(III) content, but iron(II) hydroxide has a significant solubility in neutral water, as noted above, and of course is readily soluble in acidic media. 

Sebastian, S., Dillon, S.T., Lynch, J.G., Blalock, L.T., Balon, E., Lee, K.T., Comstock, L.E., Conlan, J.W., Rubin, E.J., Tzianabos, A.O., Kasper, D.L. A defined O-antigen polysaccharide mutant of Francisella tularensis live vaccine strain has attenuated virulence while retaining its protective capacity. Infect Immun 75 (2007) 2591-2602. 

The nature of the corrosion product plays an important part in deciding if the reaction occurs through a film or film-free reaction. This can distinguish electrochemical from chemical reactions. If a film is formed due to the oxidation of the metal, the properties of this film, such as coverage and protection capacity, partial pressure, resistivity, porosity,... 

A large variation of the duration of the detoxification was noted (Table 1). Only five patients could be treated for less than 10 weeks, while twelve other patients had to be treated for up to 91 weeks. The treatment was discontinued in patients in whom both s-Al and the increment of s-Al after desferrioxamine treatment were below 50 pg/L at two successive occasions). The treatment duration was significantly related to the residual diuresis as all patients with a residual diuresis of a liter/day or more could be treated for less than two months (Fig. 2). Other studies have also established the protective capacity of an even minimal functioning kidney [30, 67]. None of the patients died during treatment with desferrioxamine, and six patients (patient Nos. 11-13, 22, 25, 26) died more than one year after termination of the desferrioxamine treatment, due to causes unrelated to the A1 intoxication. As of November 2001, more than five years after the intoxication episode, 12 of the 17 surviving patients (patient Nos. 11, 12, 14, 16-24) are still alive and none of the patients developed any clinical signs of Al toxicity, like speech disturbances, cognitive defects, bone fractures or dementia-like symptoms. 

Table 5 Protective capacity of promazine in infected mice...

Table 21 Determination of the in vivo protective capacity of flupenthixol in mice receiving a challenge dose 1.85 x 109 CFU units of Salmonella typhimurium NCTC 74 in 0.5 ml nutrient broth ...

Table 25 Determination of protective capacity of YS06 in vivo ...

Table 29 Determination of mouse protective capacity of YS19 and YS19...

Fig. 2.8. Factors controlling the production of free radicals in cells and tissues (Rice-Gvans, 1990a). Free radicals may be generated in cells and tissues through increased radical input mediated by the disruption of internal processes or by external influences, or as a consequence of decreased protective capacity. Increased radical input may arise through excessive leukocyte activation, disrupted mitochondrial electron transport or altered arachidonic acid metabolism. Delocalization or redistribution of transition metal ion complexes may also induce oxidative stress, for example, microbleeding in the brain, in the eye, in the rheumatoid joint. In addition, reduced activities or levels of protectant enzymes, destruction or suppressed production of nucleotide coenzymes, reduced levels of antioxidants, abnormal glutathione metabolism, or leakage of antioxidants through damaged membranes, can all contribute to oxidative stress.

Some metals such as nickel, copper and aluminum yield fluoride films of low permeability which prevent further reactions. However, this protective capacity is lost at elevated temperatures. Metals such as molybdenum, tungsten and titanium form volatile metal fluorides. 

It is noteworthy that the assistance and protection provisions in Article X provide for a variety of mechanisms to deal with possible future CW threats, no matter how they might come about. The CWC not only establishes the right of States Parties to protect themselves against chemical weapons but calls for enhanced cooperation between the parties in the area of exchanging equipment, material and information needed for protective purposes and requires the Organisation as a whole to help States Parties improve their protective capacity and to provide assistance to those States Parties that are not in a position to acquire protection for themselves, by the coordination and delivery of such protection under procedures of the Organisation. ... 

The photostability of sunscreens has been, since the 1990s, primarily a UV-A issue due to the fact that no agreed method was (and still isn t at this time) available to assess the protective capacity of a sunscreen preparation towards UV-A radiation. As in the early days, the photostability of the UV filter or the sunscreen preparation itself was tentatively used instead of a skin-related end point. 

The influence of molecular structures and substituents on the antiozonant properties of a series of related aromatic diamine compounds was studied. The relative effectiveness of the compounds was determined by viscometric techniques and by comparison of the rate of degradation of protected vuicanizates. Results indicate that unsymmetrical p-phenylenediamine derivatives are less effective than analogous symmetrical compounds as antiozonants. The protective capacity of the antiozonants decreases as the size or number of the N-hydrogen substituents, or the distance between the amine groups, increases. The comparative stability of the free radicals of aryl diamines, in terms of the theory of resonance, is utilized to explain the relative inhibiting properties of the chemicals examined. 

A simple, rapid, and reliable viscometric technique for evaluating the protective capacity of commercially available materials as inhibitors of ozone-induced polymer chain scission has been described (1). This work included the results of an evaluation of several chemicals such as A,A -di-sec-butyl-p-phenylenediamine, nickel dibutyl di-thiocarbamate, l-(m-aminophenyl)-2,5-dimethylpyrrole, and 2,6-di-tert-butyl-4-methyl-phenol as antiozonants A,A -di-sec-butyl-p-phenylenediamine exhibited superior inhibiting characteristics. However, because of the potential toxic effects and relatively high vapor pressure of this chemical, its use is considered impractical. 

Influence of Amine-Group Substituents. Figure 6 shows the influence of the number of amine-group substituents on the protective capacity of aromatic diamine chemicals. An increase in the number of AT-phenyl-group sustituents produces a corresponding decrease in the antiozonant properties of the diamine. 

Influence of Ring Substituents. The influence of para ring substituents on the antiozonant characteristics of aromatic diamine chemicals is shown in Figure 7. Data indicate that the protective capacity of the additives decreases as the distance between the amine groups of the aromatic diamines increases. 

---