Synergism, definition

In the following, several terms used to describe interactions between chemicals are mentioned as well as basic concepts used in the hazard and risk assessment of chemical mixmres. The description of these basic concepts, first outlined by Bliss (1939) and Placket and Hewlett (1952), are based on the publications by Konemann and Pieters (1996), Cassee et al. (1998), and Groten et al. (2001). The definitions of additivity, synergism, antagonism, and potentiation are those of Klaassen (1995) and Seed et al. (1995). 

It should be noted that synergism and potentiation may be defined in the reverse way in some texts, and the term insecticide synergists," as defined here, usually reflects potentiation. The definition used here is the same as that used in pharmacology. 

Interaction Chemicals influence each other by physical, chemical, or biological means before or after reaching the molecular site of toxic action. Toxicological interactions are responses that deviate from those expected under some definition of additivity (e.g., following the concepts of IA or CA). The most commonly used terms for interaction are synergism and antagonism. ... 

The human data, as well as the animal studies indicate that cannabinoids may ameliorate some symptoms of MS. Unfortunately, a definitive large-scale study has yet to be performed. Such a study should take into account that (a) the placebo effect in MS is very high (b) the effective doses recorded are close to, or identical with the doses that cause cannabimimetic effects (c) cannabis (marijuana, hashish) is obviously not identical to zf9-THC, and that other constituents may synergize THC action (d) smoking cannot be compared with oral administration, and (e) the anal route of administration [141] may be a preferred one. 

Simultaneous Interaction. In the literature, the interaction of BR with auxin has been reported to be additive or synergistic depending on experimental systems and conditions (5). In cucumber hypocotyl sections, the interaction is definitely synergistic (5). The synergism is especially significant when the concentration of one of the two is suboptimal. The interaction at their optimal concentrations is synergistic only during the early period of incubation and becomes additive finally. A synthetic auxin, 2,4-D also interacts with BR similarly (8). 

A computer survey of the patent literature made a year ago came up with 515 recent patents claiming herbicidal synergies. A perusal of the abstracts of 45 of them, chosen as a sample, showed that the patent community uses a broader definition of synergy than used here they believe that there is a synergism when two herbicides control more weed species than each separately. This would better be termed "complementarity. The overlap of control range allows a lowering of herbicidal rates, which may or may not be due to a metabolic... 

From the relations upon which equations 11.1 and 11.2 are based and the definition for synergism or antagonism (negative synergism) of this type, it has been shown mathematically (Hua, 1982b, 1988) that the conditions for synergism or antagonism, in surface tension reduction efficiency to exist are ... 

FIGURE 17.4 Definition of synergism and antagonism between two stabilizers. 

The combination showed definite synergism, with a rapid show of the LSD effects (within fifteen minutes) and an almost three plus effect. 

Figure 3. An illustration of how the interaction term, / (inset), assumes a positive value when the concentration response profile of the mixture is shifted leftward (large dark arrow) relative to the null condition derived from a simple averaging model (see Fig. 1 legend for definitions). Positive values for / are defined as synergisms. Hence the component in a mixture combine to yield a repellent effect that is greater (i.e., the birds eats/drinks less) than that predicted from a simple averaging model.

The term compatibility has been used in different ways. The hard definition is correlated with miscibility on a molecular scale however, other definitions have been proposed based on the properties-composition relationships. Some define the term compatible as those blends that show synergism in some properties or even when they show some valuable end properties. 

The expression unusual has been deliberately been left open ended or ill defined since the effect will almost certainly differ between systems having different phenomenological bases for cooperativity or synergism. Nevertheless, a rather useful working definition might be a rate or selectivity dependence which cannot be explained as a strictly additive effect of the metal(s) used. Having said that, the homometallic and heterobimetallic catalytic binuclear elimination reactions (CBERs) which are the focus of this chapter have very well-defined rate dependences which can be traced back to the topology of the reaction mechanisms. 

To best effectiveness, purposefully designed and synthesized materials could emerge from synergic work between electroanalysts/electrochemists and chemists who are experts specifically in synthesis. The importance of gathering suitable expertise from many different scientific and technological fields should be emphasized. Competences as to the matrices on which their work should also contribute, in order to address the properties of the device developed to the goal pursued amperometric sensing is definitely a deeply interdisciplinary field. 

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