Physical matrix

Physical (matrix) Some Very few Very few Some... 

Test system (EPA) Any animal, plant, microorganism, chemical or physical matrix, including but not limited to soil or water, or subparts thereof, to which the test, control, or reference substance is administered or added for the study. 

Alternatively (or initially) the mixture is treated as a whole and tested in its crude state. The advantage of this strategy includes the relevancy of the tested sample to its environmental counterpart, decreased potential for artefact formation, and inclusion of combined effects of chemicals in the mixture. Moreover if the mixture is representative of others in its class (e.g., diesel emissions from different sources would share certain characteristics), it may be possible to extrapolate results across samples. This method also circumvents the labor-intensive process of individual testing of multiple chemicals. But sometimes a complex mixture is too cytotoxic to be tested directly in a bioassay. Furthermore, it may be incompatible with the test system because of the physical matrix. Other disadvantages include the inability to specify the constituent of the mixture responsible for the toxicity, as well as potential masking effects (e.g., the masking of mutagenicity by cytotoxicity). 

Since so many instances of environmental contamination involve soil, and since soil is a highly complex biological, chemical, and physical matrix, we have provided a full chapter (Chapter 2) on the influences of soil properties on bioremediation processes. These influences must be understood if bioremediation is ever to become a dependable technology. 

Heavy disintegration. This level of decay can be identified when whole areas of the structure have been assimilated, and only dissociated portions are left. The physical matrix has been seriously violated so that it no longer works as a unit. Degradation is apparent through the loss of mechanical properties, as well as through evidence from byproducts (frass, macerated cells, surface hyphae) and often audible sounds as dissociated sections rattle or rub together. 

It is essential quality in a model that it should be capable of having a life of its own. It may not, in practice, need to be sundered from its physical matrix. It may be a poor, an ill-favored thing when it is by itself. But it must be capable of having this independence. 

In most drug-eluting applications, the drug is physically matrixed by dissolving or melting with a polymer. Another approach has also been reported in which a drug is chemically attached as a side group to a polymer (16). If a... 

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