Borderline

Flaws under this dimension will be under the critical signal-to-noise ratio of 2 1 for a given film system class and for instance for the borderline film of class C5 a flaw must be already -21 % deeper for perception than for the film of class C4. 

Besides the five classical types there are borderline cases which, as in most classifications, are difficult to assign to one group rather than another. There are indeed a not inconsiderable number of isotherms which are difficult to fit into the classification at all. 

The borderlines between the different classes are not hard and fast, depending as they do both on the shape of the pores and on the nature (especially the polarizability) of the adsorptive molecule. Thus, the highest value of w (and therefore of p/p ) at which the enhancement of adsorption occurs, i.e. the upper limit of the micropore range, will vary from one adsorptive to another (cf. Chapter 4). 

Compositional aspects that are regulated include a label statement within 1.5% for table wine (for dessert wines, 1.0%) of the wine s alcohol content. Eor tax identity reasons, alcohol of 7—14% is required for table wines and 17—21% for dessert and appetizer wines. Eederal excise tax rates are 0.28/L for table wines, 0.41/L for wines 14—21% alcohol, and 0.83/L for those (rare) >21-24%. Coolers made with wine become taxable at 0.5% and are taxed as table wine above 7% alcohol. Sparkling wine is taxed at 0.90/L and carbonated at 0.87/L. The borderline to incur these taxes is CO2 above 3.92 g/L. 

SAE Viscosity grade Viscosity, mPa-s(=cP) at °C Borderline pumping temperature, °C Minimum Maximum... 

Inferred reserves are producible, but the assumption of their presence is based on limited physical evidence and considerable geologic extrapolation. This places them on the borderline of being considered undiscovered, and the accuracy of the estimate is very poor. 

Oleum Equipment ndPiping. The traditional material of constmction for oleum is carbon steel. Relatively low oleum velocities must be used in steel piping to prevent excessive corrosion. The corrosiveness of oleum decreases with increasing SO concentration. Eor oleum concentrations <5% SO, carbon steel is not recommended because of excessive corrosion. Steel is borderline from 5% to about 15% SO, depending on temperature. 

Monovalent cations are compatible with CMC and have Httle effect on solution properties when added in moderate amounts. An exception is sUver ion, which precipitates CMC. Divalent cations show borderline behavior and trivalent cations form insoluble salts or gels. The effects vary with the specific cation and counterion, pH, DS, and manner in which the CMC and salt are brought into contact. High DS (0.9—1.2) CMCs are more tolerant of monovalent salts than lower DS types, and CMC in solution tolerates higher quantities of added salt than dry CMC added to a brine solution. 

Electroless reactions must be autocatalytic. Some metals are autocatalytic, such as iron, in electroless nickel. The initial deposition site on other surfaces serves as a catalyst, usually palladium on noncatalytic metals or a palladium—tin mixture on dielectrics, which is a good hydrogenation catalyst (20,21). The catalyst is quickly covered by a monolayer of electroless metal film which as a fresh, continuously renewed clean metal surface continues to function as a dehydrogenation catalyst. Silver is a borderline material, being so weakly catalytic that only very thin films form unless the surface is repeatedly cataly2ed newly developed baths are truly autocatalytic (22). In contrast, electroless copper is relatively easy to maintain in an active state commercial film thicknesses vary from <0.25 to 35 p.m or more. 

The main features of the effect of structure on the site of attack are summarized in Table 3, and can be understood in.terms of a borderline 5n2 (59CRV737) transition state (48) which somewhat resembles an 5n1 transition state in charge distribution because C—O bond breaking runs ahead of Nu—C bond making. 

Alkyl groups under nonacidic conditions sterically deflect nucleophiles from C, but under acidic conditions this steric effect is to some extent offset by an electronic one the protonated oxirane opens by transition states (Scheme 40) which are even more 5Nl-like than the borderline Sn2 one of the unprotonated oxirane. Thus electronic factors favor cleavage at the more substituted carbon, which can better support a partial positive charge the steric factor is still operative, however, and even under acidic conditions the major product usually results from Cp attack. 

Two further compounds are on the borderline of stability. The oxathiirane (14), obtained by photorearrangement of a thioketone 5-oxide, could be characterized by its UV spectrum (76JCS(P1)1404). Thiazirine (15) was stable only at 15 K (78JCS(P1)746). 

Short-time tests also can give misleading results on alloys that form passive films, such as stainless steels. With Borderline conditions, a prolonged test may be needed to permit breakdown of the passive film and subsequently more rapid attack. Consequently, tests run for long periods are considerably more reahstic than those conducted for short durations. This statement must be quahfied by stating that corrosion should not proceed to the point at which the original specimen size or the exposed area is drastic y reduced or the metal is perforated. 

This simulation performed on the borderline of up-to-date computational capabilities is beyond the framework of the semiclassical approximation, since A is comparable with coq. As far as real systems are concerned, such simulations are often hardly feasible for higher barriers and more degrees of freedom. On the other hand, as tests show (see section 4.1 and sequel), semiclassical methods cost incomparably less, being at the same time quite accurate, even when the barrier is not too high. 

The goal of all economic evaluations should be to eliminate all unprofitable projects. Some borderline, and perhaps a few good projects, will be killed along with the bad ones. However, it is much better to pass up several good projects than to build one loser. 

SECTION 5.3. DETAILED MECHANISTIC DESCRIPTION AND BORDERLINE MECHANISMS... 

The ionization and direct displacement mechanisms can be viewed as the extremes of a mechanistic continuum. At the 8 1 extreme, there is no covalent interaction between the reactant and the nucleophile in the transition state for cleavage of the bond to the leaving group. At the 8 2 extreme, the bond formation to the nucleophile is concerted with the bondbreaking step. In between these two limiting cases lies the borderline area, in which the degree of covalent interaction between the nucleophile and the reactant is intermediate between the two limiting cases. The concept of ion pairs is important in the consideration of... 

The importance of solvent participation in the borderline mechanisms should be noted. Nucleophilic participation is minimized by high electronegativity, which reduces the Lewis basicity and polarizability of the solvent molecules. Trifluoroacetic acid and perfiuoro alcohols are among the least nucleophilic of the solvents used in solvolysis studies. These solvents are used to define the characteristics of reactions proceeding without nucleophilic solvent participation. Solvent nucleophilicity increases with the electron-donating capacity of the molecule. The order trifluoroacetic acid < trifluoroetha-nol <acetic acid < water < ethanol gives a qualitative indication of the trend in solvent nucleophilicity. More will be said about solvent nucleophilicity in Section 5.5. 

Studies of the stereochemical course of rmcleophilic substitution reactions are a powerful tool for investigation of the mechanisms of these reactions. Bimolecular direct displacement reactions by the limSj.j2 meohanism are expected to result in 100% inversion of configuration. The stereochemical outcome of the lirnSj l ionization mechanism is less predictable because it depends on whether reaction occurs via one of the ion-pair intermediates or through a completely dissociated ion. Borderline mechanisms may also show variable stereochemistry, depending upon the lifetime of the intermediates and the extent of internal return. It is important to dissect the overall stereochemical outcome into the various steps of such reactions. 

Many other cations besides the norbomyl cation have nonclassical structures. Scheme 5.5 shows some examples which have been characterized by structural studies or by evidence derived from solvolysis reactions. To assist in interpretation of the nonclassical stmctures, the bond representing the bridging electron pair is darkened in a corresponding classical stmcture. Not surprisingly, the borderline between classical stmctures and nonclassical stmctures is blurred. There are two fundamental factors... 

There are alternatives to the addition-elimination mechanism for nucleophilic substitution of acyl chlorides. Certain acyl chlorides are known to react with alcohols by a dissociative mechanism in which acylium ions are intermediates. This mechanism is observed with aroyl halides having electron-releasing substituents. Other acyl halides show reactivity indicative of mixed or borderline mechanisms. The existence of the SnI-like dissociative mechanism reflects the relative stability of acylium ions. 

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