Synergizers

Tyson, J. P. Atomic Spectrometry and Plow Injection Analysis A Synergic Gombination, Anal Chim. Acta 1988, 214, 57-75. 

Chelidomne [476-32-4] CHEMASIM Chemcalc 5 Chemcalc 6 CHEh OC Chem-Fish Synergized Chemicalabstracts... 

E. D. Wed, "Additivity, Synergism and Antagonism in Flame Retardancy - Recent Developments," paper presented at 3rdMnnualBCC Conference on... 

Although aminyl radicals are stable towards oxygen, they can oxidi2e other aromatic amines, phenols and thiols (10), and regenerate the diarylamine. Thus, mixtures of phenols and diarylamines frequendy show better antioxidant activity than either one alone. This is called synergism. 

SCE increases absolute colony number and surviving fraction of CEU-E, CEU-G, and CEU-GM in kradiated human BM. An increase in the fraction of CDSd cells in the radioresistant S-phase has been noted, which suggests a possible mechanism (184). A cautionary note has been sounded about attempting to predict interactions between SCE and CSEs in hemopoieticaHy deprived individuals (185). Although SCE synergizes with GM-CSE or GM-CSE and lL-3 to increase CEU-GM in vitro, no such effect has been found in vivo. 

G-CSFPlus WR-2721. Because glucan is a potent inducer of several hemopoietic cytokines, it has been suggested that specific hemopoietic cytokines may also stimulate hemopoiesis and synergize with WR-2721 (252). Based on values, combining WR-2721 (4 mg/mouse ip 30-min... 

Fig. 4. Accelerator synergism where A is tetra-/ro-butyl thiuram disulfide and B is zinc di-/ro-butyl dithiocarbamate. To convert MPa to psi, multiply by 145.

Synergism is appHed to a situation where the effect of two or more chemicals that have common mechanism of toxicity, given together, is significantly greater than that expected from considerations on the toxicity of each material alone. This differs from potentiation in that both materials contribute to the toxic injury, and the net effect is always greater than additive. 

Clavulanic acid has only weak antibacterial activity, but is a potent irreversible inhibitor for many clinically important P-lactamases (10—14,57,58) including penases, and Richmond-Sykes types 11, 111, IV, V, VI ([Bacteroides). Type I Cephases are poorly inhibited. Clavulanic acid synergizes the activity of many penicillins and cephalosporins against resistant strains. The chemistry (59—63), microbiology (64,65), stmcture activity relationships (10,13,60—62,66), biosynthesis (67—69), and mechanism of action (6,26,27,67) have been reviewed. 

Table 3. Synergism Between a Hindered Phenol and a Thiosynergist ...

The toughness induced in ceramic matrices reinforced with the various types of reinforcements, that is, particles, platelets, whiskers, or fibers, derives from two phenomena crack deflection and crack-tip shielding. These phenomena usually operate in synergism in composite systems to give the resultant toughness and noncatastrophic mode of failure. 

Competition Predation Commensalism Mutualism Synergism Antibiosis A race for nutrients and space One feeds on another One lives off another with negligible help or barm Each benefits the other Combination has cooperative metabolism One excretes a factor harmful to the other... 

The corrosion of copper by carbonic acid deserves special attention. There is a synergism between oxygen and carbonic acid with regard to corrosion. Carbonic acid in the absence of oxygen is not corrosive to most copper alloys. However, corrosivity can be appreciable if oxygen is present. 

Many groups throughout the world tried to repeat the experiments using similar in vitro assays and other test systems, but without success. Current experimental data suggest additive interactions do occur between EDs, but the issue of interactive effects, and synergism in particular, will undoubtedly remain a topic of intense debate for some time to come. 

Antioxidants are today often used in combination. One reason for this is that certain combinations can exhibit in a polymer an effect sometimes found with other additives, that known as synergism. In these circumstances two antioxidants may exhibit a co-operative effect and be more powerful than either antioxidant used alone, even when the total antioxidant concentration is the same. Certain terms are sometimes encountered here and these are defined in Table 7.6. 

In commercially practical terms it may be that although synergism occurs, one additive may be sufficiently less expensive for more to be used to achieve the required stability and still give the lowest overall cost. 

In antioxidants, synergism appears to arise either from one antioxidant effectively regenerating another so that the latter does not become consumed or by the two antioxidants functioning by differing mechanisms. The latter is more important and it is easy to see how effective a combination of peroxide decomposer and chain-breaking antioxidant can be. 

Two final points should be made while considering antioxidant synergism. Firstly, some antioxidants which function by more than one mechanism are in all probability autosynergistic. Secondly, certain additives which appear to act... 

Figure 7.7. The synergism of sulphur antioxidants with carbon black as constrasted to the adverse effect shown with conventional antioxidants (in polyethylene)...

In the presence of carbon black the phenols and phenol/DLTP combinations are much less effective whilst some phenolic sulphides (e.g. Santonox) show positive synergism with carbon black. Flowever, in general terms the phenol systems tend to be reduced to about the same levels as to those to which the phenol sulphide systems are raised. Some typical figures are given in Table 10.8. 

There has been a revival of interest in recent years in antimony mercaptides as alternatives to the organo-tin stabilisers. This stems from the low level of toxicity and the strong synergism with calcium stearate. However, compared to the... 

When two antioxidants are used together, a synergistic improvement in activity usually results. Synergism can arise from three combinations (1) homosynergism — two chemically similar antioxidants (for instance, two hindered phenols) (2) autosynergism — two different antioxidants functions that are present in the same molecule (3) heterosynergism — the cooperative effect between mechanistically different classes of antioxidants, such as the combined effect of primary and secondary antioxidants. Thus, combinations of phenols and phosphites are widely used to stabilize synthetic rubbers. 

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