Compared definitions

The configurational sequence and stereosequence coincide in this particular case because there is only one site of stereoisomerism in each constitutional repeating unit (compare Definitions 2.1.3 and 2.1.4). 

A reference method is a technique that can be accomplished with generally available equipment and that, after exhaustive investigation, has been shown to have acceptable known inaccuracy in comparison with a definitive method (Brown et al., 1976). This definition compares definitive and reference methods with regard to their inaccuracy. However, as there is no absolute method and the true value remains unknown, a classification based on this criterion remains questionable. The other criterion is precision, but methods cannot be classified as definitive or reference based on this criterion alone. Also, the third definition clearly describes the hierarchy in methods and materials. 

The similarity of ecdysteroids and brassinosteroids may cause some difficulties in their definition. Ecdysteroids were initially defined as "all compounds structurally related to ecdysone" (3). This definition would include brassinosteroids. Recently an attempt has been made by Lafont and Horn to redefine ecdysteroids (6). According to their definition one may "distinguish between true ecdysteroids as compounds where the steroid bears a cis-fused A/B ring junction, a 7-ene-6-one chromophore and a 14a-OH (irrespective of activity in a moulting hormone assay) and ecdysteroid-related compounds which do not fulfil all the above criteria (either they lack the 14a-OH, or the 7-ene, or they present one additional 4- or 14-ene double bond, etc.)" (6). The latter group would include brassinosteroids. Unfortunately, comparable definitions of brassinosteroids are not available so far. 

The preceding definitions of economic potential and total annual cost can be simplified if it is accepted that they will be used to compare the relative merits of difierent structural options in the flowsheet and difierent settings of the operating parameters. Thus items which will be common to the options being compared can be neglected. 

The two exponential tenns are complex conjugates of one another, so that all structure amplitudes must be real and their phases can therefore be only zero or n. (Nearly 40% of all known structures belong to monoclinic space group Pl c. The systematic absences of (OlcO) reflections when A is odd and of (liOl) reflections when / is odd identify this space group and show tiiat it is centrosyimnetric.) Even in the absence of a definitive set of systematic absences it is still possible to infer the (probable) presence of a centre of synnnetry. A J C Wilson [21] first observed that the probability distribution of the magnitudes of the structure amplitudes would be different if the amplitudes were constrained to be real from that if they could be complex. Wilson and co-workers established a procedure by which the frequencies of suitably scaled values of F could be compared with the tlieoretical distributions for centrosymmetric and noncentrosymmetric structures. (Note that Wilson named the statistical distributions centric and acentric. These were not intended to be synonyms for centrosyimnetric and noncentrosynnnetric, but they have come to be used that way.)... 

The problems already mentioned at the solvent/vacuum boundary, which always exists regardless of the size of the box of water molecules, led to the definition of so-called periodic boundaries. They can be compared with the unit cell definition of a crystalline system. The unit cell also forms an "endless system without boundaries" when repeated in the three directions of space. Unfortunately, when simulating hquids the situation is not as simple as for a regular crystal, because molecules can diffuse and are in principle able to leave the unit cell. 

Equation (9.23) is to be compared with the Feng and Stewart relations (9.4) which describe the fluxes in the same system under non-reactive conditions, The factor (BA coth BA - 1) has the form sketched in Figure 9.2. From the definition of B given by equation (9.19) it is seen chat 9- 0 as and each tend to zero, their ratio remaining equal to Che... 

Take two test-tubes A and B in A place about 5 ml. of neutralised tartaric acid solution and in B place 5 ml. of distilled water. To each solution add 3-4 drops of ferric chloride solution. Place a piece of white paper under the tubes, look down their length and note that A is definitely yellow compared with the control tube B. This yellow colour is given by a-hydroxy-carboxylic-acids, lactic acid, tartaric acid, citric acid. 

Extensive discussions have focused on the conformation of the alkyl chains in the interior ". It has been has demonstrated that the alkyl chains of micellised surfactant are not fully extended. Starting from the headgroup, the first two or three carbon-carbon bonds are usually trans, whereas gauche conformations are likely to be encountered near the centre of tlie chain ". As a result, the methyl termini of the surfactant molecules can be located near the surface of the micelle, and have even been suggested to be able to protrude into the aqueous phase "". They are definitely not all gathered in the centre of tire micelle as is often suggested in pictorial representations. NMR studies have indicated that the hydrocarbon chains in a micelle are highly mobile, comparable to the mobility of a liquid alkane ... 

How we report the result of an experiment is further complicated by the need to compare the results of different experiments. For example. Table 4.10 shows results for a second, independent experiment to determine the mass of a U.S. penny in circulation. Although the results shown in Tables 4.1 and 4.10 are similar, they are not identical thus, we are justified in asking whether the results are in agreement. Unfortunately, a definitive comparison between these two sets of data is not possible based solely on their respective means and standard deviations. 

In the extreme case where rjrj =0 because both rj and i2 equal zero, the copolymer adds monomers with perfect alternation. This is apparent from the definition of r, which compares the addition of the same monomer to the other monomer for a particular radical. If both r s are zero, there is no tendency for a radical to add a monomer of the same kind as the growing end, whichever species is the terminal unit. When only one of the r s is zero, say rj, then alternation occurs whenever the radical ends with an Mj unit. There is thus a tendency toward alternation in this case, although it is less pronounced than in the case where both r s are zero. Accordingly, we find increasing tendency toward alternation as rj 0 and rj 0, or, more succinctly, as the product X1X2 0. 

At this point it is useful to compare the result we have obtained with the expected behavior of P(0) that we anticipated from the definition of this quantity ... 

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

The definition of polymer thermal stabiUty is not simple owing to the number of measurement techniques, desired properties, and factors that affect each (time, heating rate, atmosphere, etc). The easiest evaluation of thermal stabiUty is by the temperature at which a certain weight loss occurs as observed by thermogravimetric analysis (tga). Early work assigned a 7% loss as the point of stabiUty more recentiy a 10% value or the extrapolated break in the tga curve has been used. A more reaUstic view is to compare weight loss vs time at constant temperature, and better yet is to evaluate property retention time at temperature one set of criteria has been 177°C for 30,000 h, or 240°C for 1000 h, or 538°C for 1 h, or 816°C for 5 min (1). 

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