Properties beliefs

The discovery in 1954 that fluorination of the glucocorticoid hormone cortisol could bring about remarkable changes in the biological properties of the hormone was entirely unexpected and violated the then prevalent belief that synthetic variants could not surpass a naturally occurring hormone in its biological activity. Because of the impact that fluorination of steroids has had on subsequent developments in this area the history of the discovery of fluorocortisol will be briefly recounted. 

Reductionist World-View Holistic World-View a shift away from a long held belief that complex self-organized behavior requires a complex underlying dynamics and/or substructure towards the new notion that complexity is an emer-gent/holistic phenomenon that often arises from the interactions among a large assemblage of otherwise simple parts i.e. the properties of the parts must be understood as a dynamics of whole. 

Corrosion (spontaneous dissolution) of the catalyticaUy active material, and hence a decrease in the quantity present. Experience shows that contrary to widespread belief, marked corrosion occurs even with the platinum metals. For smooth platinum in sulfuric acid solutions at potentials of 0.9 to 1.0 V (RHE), the steady rate of self-dissolution corresponds to a current density of about 10 A/cm. Also, because of enhanced dissolution of ruthenium from the surface layer of platinum-ruthenium catalysts, their exceptional properties are gradually lost, and they are converted to ordinary, less active platinum catalysts. 

Furthermore, the role of a poly hydroxy alcohol, like ethylene glycol, seems ambiguous. As mentioned above, it is believed that the presence of ethylene glycol favours esterification of chelates. IR and NMR studies performed in [7] do not present solid proofs of such a belief. Synthetic routines with and without alcohols look the same, and the absence of alcohol seem not to influence the properties of precursors and final products. Some evidence exists enabling one to consider the esterification idea liable to more than one interpretation it has been reported in [4] that the presence of ethylene glycol does not influence the morphology of oxides. 

With traditional solvents, the solvent power of a fluid phase is often related to its polarity. Compressed C02 has a fairly low dielectric constant under all conditions (e = 1.2-1.6), but this measure has increasingly been shown to be insufficiently accurate to define solvent effects in many cases [13], Based on this value however, there is a widespread (yet incorrect ) belief that scC02 behaves just like hexane . The Hildebrand solubility parameter (5) of C02 has been determined as a function of pressure, as demonstrated in Figure 8.3. It has been found that the solvent properties of a supercritical fluid depend most importantly on its bulk density, which depends in turn on the pressure and temperature. In general higher density of the SCF corresponds to stronger solvation power, whereas lower density results in a weaker solvent. 

The preparation of both, the particles themselves and the protective surface layer, has direct influence on their cytotoxicity. It is common belief that in the case of core/shell nanoparticles, properly prepared, close shell or multiple shells such as ZnS/Si02-shells prevents the leakage of toxic elements and thus makes cytotoxicity unlikely. Naturally, a better solution is to avoid cytotoxic materials in the first place. QDs, for example, can be synthesized without utilization of any class A or B elements InP/ZnS QDs have photophysical properties comparable to those of CdSe-based systems [43, 93]. Principally, whenever a new approach for QD synthesis or coating is used or if the QDs are applied in an extreme environment that could compromise their integrity, it is recommended to assess their cytotoxicity. 

One area not discussed so far is the problem of thermodynamic properties of mixtures containing both electrolyte and nonelectrolyte components. It is the belief of the author that this problem will not be completely resolved until equations of state are developed to handle these systems. We will only make progress in this direction when we recognize this as a problem and work toward solving the problem. Anything short of this also falls short in solving the ultimate problems of these mixtures. 

Further work in this area is underway employing polyamic acid systems which are known to produce higher viscosity solutions (e.g. polyimides derived from 4,4 -oxydianiline and either BTDA or pyromellitic dianhydride). This is being carried out in the belief that higher viscosity solutions will give rise to higher quality, less brittle films and will, thereby, enable a broader spectrum of metal systems to be studied regarding the adhesive and electrical conductance properties of metal ion filled polyimides. 

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