Nonspecificity

As also noted in the preceding chapter, it is customary to divide adsorption into two broad classes, namely, physical adsorption and chemisorption. Physical adsorption equilibrium is very rapid in attainment (except when limited by mass transport rates in the gas phase or within a porous adsorbent) and is reversible, the adsorbate being removable without change by lowering the pressure (there may be hysteresis in the case of a porous solid). It is supposed that this type of adsorption occurs as a result of the same type of relatively nonspecific intermolecular forces that are responsible for the condensation of a vapor to a liquid, and in physical adsorption the heat of adsorption should be in the range of heats of condensation. Physical adsorption is usually important only for gases below their critical temperature, that is, for vapors. 

Leckband D ef a/1994 Direct force measurements of specific and nonspecific protein interactions S/oc/rem/sfry 33 4611-23... 

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic acids usually occurs with nonspecific oxidants such as KMnO, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(ll) acetate, allyiic and benzylic oxidations are aJso possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian. 1971 A. Friedrich, 1975). 

Since point x is nonspecific, Eq. (4.20) describes the fraction of observations in which no fronts cross any arbitrary point or the fraction of the area in any one experiment which is crossed by no fronts. 

Since London forces are universal and nonspecific, we shall eventually emphasize these, realizing that stronger forces may outweigh the London contribution in some systems. We anticipate the best results in nonpolar systems where London forces account for the interactions. 

Urethane sealants Urethane systems Urethane TPE Urethritis, nonspecific... 

The and Oj terms always contribute, regardless of the specific electric charge distributions ia the adsorbate molecules, which is why they are called nonspecific. The third nonspecific Op term also always contributes, whether or not the adsorbate molecules have permanent dipoles or quadmpoles however, for adsorbent surfaces which are relatively nonpolar, the polarization energy Op is small. 

FiaaHy, an analysis of the energies of adsorption on many practical polar and nonpolar adsorbents has shown not only that the magnitude of the Op term depends directly upon the polarizabiUty a, but also that the sum of all of the nonspecific terms taken together, ie, + Lp, iacreases... 

Infants maybe sensitive to doses of vitamin A [11103-57-4] in the range of 75,000—200,000 lU (22.5—60 mg), although the toxic dose in adults is probably 2—5 million lU (90.6—1.5 g). Intakes in this range from normal food suppHes without oral supplements are simply beyond imagination (79). Vitamin D [1406-16-2] toxicity is much more difficult to substantiate clinically. Humans can synthesize active forms of the vitamin in the skin upon irradiation of 7-dehydrocholesterol. Toxic symptoms are relatively nonspecific, and dangerous doses seem to He in the range of 1000—3000 lU/kg body wt (25—75 flg/kg body wt) (80). Cases of toxicity of both vitamins E and K have been reported, but under ordinary circumstances these vitamins are considered relatively innocuous (81). 

The advantages of homogenous immunoassays are simple formats and rapid data output producing user-friendly and cost-effective products. Technical challenges to consider, however, are the necessity to remove or minimize background interference from the reagents and nonspecific binding reactions. 

Interferons (lENs) (52,53), a family of species-specific vertebrate proteins, confer nonspecific resistance to a broad range of viral infections, affect cell proliferation, and modulate immune responses. AH three principal interferons, a-interferon (lEN-a) produced by blood leucocytes, P-interferon (lEN-P) by fibroblasts, and y-interferon (lEN-y) by lymphocytes, also have antiviral activity. The abiUty of interferons to inhibit growth of transplantable and carcinogen-induced tumor led to research showing the direct antiproliferative and indirect immune-mediated antitumor activities (see Chemotherapeutics, anticancer). IENs have been found to be efficacious in certain malignancies and viral infections, eg, hairy cell leukemia (85% response) and basal cell carcinoma (86% response). However, the interferons do have adverse side effects (54). 

Although there is no rehable method as of this writing for induction of Ag-speciftc unresponsiveness, some degree of tolerance has been observed by use of nonspecific immunosuppressive therapy. This conclusion is supported by a decrease in the frequency of precursor T-ceUs reactive with graft HLA Ags in long-term recipients of organ transplants. 

Nonspecific immunosuppressive therapy in an adult patient is usually through cyclosporin (35), started intravenously at the time of transplantation, and given orally once feeding is tolerated. Typically, methylprednisone is started also at the time of transplantation, then reduced to a maintenance dose. A athioprine (31) may also be used in conjunction with the prednisone to achieve adequate immunosuppression. Whereas the objective of immunosuppression is to protect the transplant, general or excessive immunosuppression may lead to undesirable compHcations, eg, opportunistic infections and potential malignancies. These adverse effects could be avoided if selective immunosuppression could be achieved. Suspected rejection episodes are treated with intravenous corticosteroids. Steroid-resistant rejection may be treated with monoclonal antibodies (78,79) such as Muromonab-CD3, specific for the T3-receptor on human T-ceUs. Alternatively, antithymocyte globulin (ATG) may be used against both B- and T-ceUs. 

Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

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