Element controlling deleterious

The rare earths play three roles in the production of nodular iron. These roles are as a nodulizing element (or as the growth modifier) as a means of enhancing the nodule count (or nucleation) and, finally as controllers of deleterious elements. The use of the rare earths for each of these purposes will be described in detail in the following sections. 

The mechanism by which these deleterious elements are controlled is still a matter of speculation. Some researchers have suggested that the rare earth elements combine with the deleterious elements to form innocuous insoluble intermetallic compounds (31). However, such particles have been observed, using the electron microprobe, only when concentrations of both the rare earths and deleterious elements were well above those levels usually found in commercial practice. Even then, the composition of the particular phases was not determined. Further, the effective level of cerium at which the beneficial effects are observed suggests that the mechanism may not be simply compound formation. 

It is also interesting to note that the deleterious elements, with the exception of titanium, are elements that can be used to stabilize the iron-carbide phase. Titanium is also the only so-called deleterious element that appears to be somewhat controllable by additions of more magnesium, instead of one of the rare earths in common use (34). However, the use of rare earths... 

Little research has been reported concerning the determination of which of the rare earths normally used in the industry might be more potent in controlling these deleterious elements. 

The rare earth elements have played a key part in the discovery and commercialization of nodular iron. The efficacy of these elements in controlling the effects of deleterious elements, in nucleation, and as nodulizers has assured their continued use. 

Reaction mechanisms in thermal analysis of lipid-based materials explain the changes in their behavior due to the action of deleterious elements that promote oxidation and lead to quality degradation, such as temperature, oxygen, light, and oxidizing metals. These elements set off reactions that induce changes in the chemical, nutritional, and functional structures of oils, making them unsuitable for human consumption, and should therefore be controlled and monitored in order to prevent quality loss. 

The constituent elements of anode materials, other than the basis metal, are present whether as a result of being impurities in the raw materials or deliberate alloying additions. The impurity elements can be deleterious to anode performance, thus it is necessary to control the quality of the input materials in order to achieve the required anode performance. Since this will usually have an adverse impact on costs it is often desirable to tolerate a level of impurities and to overcome their action by making alloying additions. Alloying elements may also be added for other reasons which are important to anode production and performance. These matters are discussed in this section. 

Coal contains most of the elements of the periodic table, the majority of which are present in concentrations of 100 ppm or less. Many of these trace elements are toxic to plant and animal life, even at low levels. Because U.S. power plants consune on the order of 600 million tons of coal annually for the production of electricity (1), coal combustion can mobilize thousands of tons of potentially hazardous trace elements into the environment each year. Due to the large quantities of coal combusted, even trace amounts of toxic elements present in the coals can accumulate to hazardous levels. Also, potentially deleterious effects of particulate emissions from coal combustion may be enhanced since many trace elements are surface-enriched (2) and concentrate preferentially in the smaller, more respirable particle sizes (3). Substantial amounts of some elements, such as As, Hg, and Se, are in the vapor phase in flue gases from coal combustion and are essentially unaffected by most particle control devices. Aside from the potential detrimental environmental aspects, trace elements in coal can pose adverse technological... 

Synthetic polyanionic iinmunomodulators present another approach for the control of neoplasia. These agents activate host elements to become cytotoxic to tumor cells thus eliminating or reducing the tumor size while the activated elements do not appear to be harmful to normal cells. These polyanionic polymers are not, however, void of toxic effects but it appears that these deleterious effects are indeed side-effects and not directly caused by the interaction of the immunomodulator with normal cells. 

---