Obscuration

SWS are useful to obtain direct indications of hydrocarbons (under UV light) and to differentiate between oil and gas. The technique is applied extensively to sample microfossils and pollen for stratigraphic analysis (age dating, correlation, depositional environment). Qualitative inspection of porosity is possible, but very often the sampling process results in a severe crushing of the sample thus obscuring the true porosity and permeability. 

While bulk viscosity is a relatively obscure property of a liquid or a solid... 

Lin et al. [70, 71] have modeled the effect of surface roughness on the dependence of contact angles on drop size. Using two geometric models, concentric rings of cones and concentric conical crevices, they find that the effects of roughness may obscure the influence of line tension on the drop size variation of contact angle. Conversely, the presence of line tension may account for some of the drop size dependence of measured hysteresis. 

The nomesonant background prevalent in CARS experiments (discussed above), although much weaker than the signals due to strong Raman modes, can often obscure weaker modes. Another teclmique which can suppress the nonresonant background signal is Raman induced Kerr-efifect spectroscopy or RIKES [96, 97]. 

With relatively simple spectra, it is usually possible to extract the individual coupling constants by inspection, and to pair them by size in order to discover what atoms they coimect. However, the spectra of larger molecules present more of a challenge. The multiplets may overlap or be obscured by the presence of several unequal but similarly sized couplings. Also, if any chiral centres are present, then the two hydrogens in a... 

The relation between the dusty gas model and the physical structure of a real porous medium is rather obscure. Since the dusty gas model does not even contain any explicit representation of the void fraction, it certainly cannot be adjusted to reflect features of the pore size distributions of different porous media. For example, porous catalysts often show a strongly bimodal pore size distribution, and their flux relations might be expected to reflect this, but the dusty gas model can respond only to changes in the... 

Meanwhile fit up a Claisen flask (of about 175 ml. capacity) with a fine capillary and thermometer (see Fig. 12(A), p. 29), taking care that the range of temperature of 70°-100° is not obscured by the cork. Then filter the crude ester at the pump... 

Enzymes are proteins of high molecular weight, several of which have been isolated in a pure State consequently their precise nature is in some instances still obscure. They form solutions in water and in dilute salt solutions, and are precipitated when such solutions are saturated with ammonium sulphate. 

The state of nitric acid in g8-ioo% sulphuric acid In this section the pioneering work of Hantzsch will several times he mentioned. That later techniques made it necessary to modify his conclusions should not be allowed to obscure the great originality of his approach since investigations using these media provided the most compelling evidence for the existence of the nitronium ion. 

If this electrostatic treatment of the substituent effect of poles is sound, the effect of a pole upon the Gibbs function of activation at a particular position should be inversely proportional to the effective dielectric constant, and the longer the methylene chain the more closely should the effective dielectric constant approach the dielectric constant of the medium. Surprisingly, competitive nitrations of phenpropyl trimethyl ammonium perchlorate and benzene in acetic anhydride and tri-fluoroacetic acid showed the relative rate not to decrease markedly with the dielectric constant of the solvent. It was suggested that the expected decrease in reactivity of the cation was obscured by the faster nitration of ion pairs. 

Primary carbon Secondary a carbon Tertiary a carbon 1090-1060 (m) 1140-1035 (m) 1240-1020 (m) CN stretching Two bands but often obscured. Strong band at 800 cm Two bands. Strong band also at 745 cm i... 

The picture therefore remains obscure. The degree of localization may well depend on variable factors such as the purity of the surface (ultra high vacuum is now known to be essential), the temperature, and the magnitude of the lattice parameters relative to the (rather large) size of the xenon atom. 

The results of a comparison between values of n estimated by the DRK and BET methods present a con. used picture. In a number of investigations linear DRK plots have been obtained over restricted ranges of the isotherm, and in some cases reasonable agreement has been reported between the DRK and BET values. Kiselev and his co-workers have pointed out, however, that since the DR and the DRK equations do not reduce to Henry s Law n = const x p) as n - 0, they are not readily susceptible of statistical-thermodynamic treatment. Moreover, it is not easy to see how exactly the same form of equation can apply to two quite diverse processes involving entirely diiferent mechanisms. We are obliged to conclude that the significance of the DRK plot is obscure, and its validity for surface area estimation very doubtful. 

The initiators which are used in addition polymerizations are sometimes called catalysts, although strictly speaking this is a misnomer. A true catalyst is recoverable at the end of the reaction, chemically unchanged. Tliis is not true of the initiator molecules in addition polymerizations. Monomer and polymer are the initial and final states of the polymerization process, and these govern the thermodynamics of the reaction the nature and concentration of the intermediates in the process, on the other hand, determine the rate. This makes initiator and catalyst synonyms for the same material The former term stresses the effect of the reagent on the intermediate, and the latter its effect on the rate. The term catalyst is particularly common in the language of ionic polymerizations, but this terminology should not obscure the importance of the initiation step in the overall polymerization mechanism. 

Randall used C-NMR to study the methylene spectrum of polystyrene. In 1,2,4-trichlorobenzene at 120°C, nine resonances were observed. These were assumed to arise from a combination of tetrads and hexads. Using m and r notation, extend Table 7.8 to include all 20 possible hexads. Criticize or defend the following proposition Assuming that none of the resonances are obscured by overlap, there is only one way that nine methylene resonances can be produced, namely, by one of the tetrads to be split into hexads while the remaining tetrads remain unsplit. 

To apply these ideas to solution nonideality, we consider a theory developed by Flory and Krigbaum. This is only one of several approaches to the problem, but it is one which can be readily outlined in terms of material we have already developed. We shall only sketch the highlights of the Flory-Krigbaum theory, since the details are complicated and might actually obscure the principal ideas. 

Polydispersity obscures the nature of the average obtained, although the possibility of extracting more than one kind of average from the same data under optimum conditions partially offsets this. 

There is no official or universally accepted definition of what constitutes a "microemulsion." In fact, for several years, some leading scientists in microemulsion research considered the term to be an unnecessary and even an unfortunate one. Nevertheless (Table 1), during the years from about 1975 to 1980 the word ascended from obscurity to ubiquity. By the end of 1996 there were 13 widely available Knglish-language books (1 9) with the word "Microemulsion" in their tides (10). About 70 more books on surfactants are in print, of which those on industrial appHcations (9,11—18), and environmental effects (19—21) are of particular interest here. 

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