Water terms Links

A further important interaction, namely, that between an active substance and water, can be studied by DSC and TSC (28). To illustrate this case, we will present results obtained with a drug manufactured in three states labeled hydrated hemihydrate (HEMI), monohydrate (MONO), and freeze-dried (FD) forms. The last is mostly amorphous and absorbs water in nonstoichiometric quantities. The other two forms are highly crystalline and contain specific ratios of water per active molecule. Thermogravimetric experiments have shown that water is linked between two active molecules for the hemihydrate, whereas the distribution is homogeneous and the ratio unimolecular for the monohydrate. Moreover, two different hemihydrate batches obtained by two different industrial processes have been analyzed. Complementary studies have shown that the batch labeled PR, is more crystalline and more stable than the PR2 batch in terms of the transition to the monohydrate form. 

In multimedia box models, the environmental fate of a chemical is described by a set of coupled mass-balance equations for all boxes of the model. These equations include terms for degradation, inter-media exchange such as settling and resuspension of particles, and transport with air and water flows [19,20]. Equations for different boxes are coupled by inter-media exchange terms (linking different environmental media) and terms for trans-... 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

The excess of evaporation from the oceans is made up for by runoff from the land. Although this flux is much smaller than precipitation and ET, it is a major link in many cycles and is of particular importance to humans in terms of water supply. Runoff can be broadly categorized into subsurface, or groundwater, flow and surface flow, consisting of overland runoff and river discharge. 

This subject can be considered in terms of five different types of molecules or materials (a) biologically inert, water-insoluble polymers (b) water-insoluble polymers that bear biologically active surface groups (c) water-swellable polymeric gels, or amphiphilic polymers that function as membranes (d) water-insoluble but bioerodable polymers that erode in aqueous media with concurrent release of a linked or entrapped bioactive molecule and (e) water-soluble polymers that bear bioactive agents as side groups. 

The multimedia model present in the 2 FUN tool was developed based on an extensive comparison and evaluation of some of the previously discussed multimedia models, such as CalTOX, Simplebox, XtraFOOD, etc. The multimedia model comprises several environmental modules, i.e. air, fresh water, soil/ground water, several crops and animal (cow and milk). It is used to simulate chemical distribution in the environmental modules, taking into account the manifold links between them. The PBPK models were developed to simulate the body burden of toxic chemicals throughout the entire human lifespan, integrating the evolution of the physiology and anatomy from childhood to advanced age. That model is based on a detailed description of the body anatomy and includes a substantial number of tissue compartments to enable detailed analysis of toxicokinetics for diverse chemicals that induce multiple effects in different target tissues. The key input parameters used in both models were given in the form of probability density function (PDF) to allow for the exhaustive probabilistic analysis and sensitivity analysis in terms of simulation outcomes [71]. 

Nevertheless, the T1 and NOE values are found to be unchanged from the solution to the gel of water content 75% and 53%. As discussed already in Section 2.1, it is very difficult to analyse such relaxation parameters in terms of a single correlation time. The calculated correlation times are found to give consistent values among those obtained from the Ti, T2, and NOE values with the width parameter of p = 18 (PVP solution) and p = 16 (PVP gel) and b = 1000. As the degree of cross-linking is increased, a discrepancy in the correlation times still occurs (a factor of 3 at 75%) but is much improved by this treatment. 

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