Differences in practice

As is the case for diatomic molecules, rotational fine structure of electronic spectra of polyatomic molecules is very similar, in principle, to that of their infrared vibrational spectra. For linear, symmetric rotor, spherical rotor and asymmetric rotor molecules the selection mles are the same as those discussed in Sections 6.2.4.1 to 6.2.4.4. The major difference, in practice, is that, as for diatomics, there is likely to be a much larger change of geometry, and therefore of rotational constants, from one electronic state to another than from one vibrational state to another. 

The transport number is a measure of the permselec tivity of a membrane. If, for example, a membrane is devoid of coions, then all current through the membrane is carried by the counterion, and the transport number = 1. The transport numbers for the membrane and the solution are different in practical ED applications. 

The RP systems currently in force differ in practice, first in accordance with the size of the market covered. This in turn depends on the equivalence criterion chosen to classify drags, and also on the inclusion or otherwise of patented drags. 

We listed many examples early in this chapter, and they can be quite different in practice, from the msting of iron to the toasting of dough to the roasting of ore. The reactant A could be a gas or a liquid, and the film could be a sohd or liquid. The migration of A through the reacted film could be diffusion of A dissolved in C or permeation of A through a porous film of C. We describe this by a diffusion coefficient D s, but the value of D/ s and the mechanism by which transport occurs will not be discussed here. 

The primary results of economic evaluations usually is a comparison of average, or pooled, differences in costs and differences in effects among patients who received the therapies under study. It is an open question, however, whether pooled results are representative of the results that would be observed in the individual centers or countries that participated in the study. In some, the therapy may provide good value for the costs, whereas in others it may provide poor value. Three reasons commonly cited for these differences are differences in practice patterns (i.e., medical service use), differences in absolute and relative prices for medical service use (i.e., unit costs), and differences in underlying morbidity/mortality patterns in different centers and countries. 

Another, and on the face of it, rather different example, is the coprecipitation of solid solution compounds, such as CulnSi and CulnSei—semiconductors of particular interest due mainly to their applicability for photovoltaic cells. It was shown, by X-ray diffraction, that the precipitate resulting from reaction between H2S and an aqueous solution containing both Cu" and In " ions was, at least in part (depending on the concentrations of the cations), single-phase CulnSi [3]. Two factors were found to be necessary for this compound formation (1) the presence of sulphide on the surface of the initially precipitated colloidal solid metal sulphide and (2) one of the cations being acidic and the other basic. The monovalent Cu cation is relatively basic, while the trivalent In cation is relatively acidic. It is not clear what the physical reason is for this latter requirement. A difference in practice between acidic and basic cations is that, in an aqueous solution of both cations, the acidic cation is more likely to be in the form of some hydroxy species (not to be confused with hydrated cations), while the basic cation is more likely to exist as the free cation. 

We have chosen the formulation of Equation 3.28 because it seems to be more consistent with our discussion in Section 3.1 about the nature of Bronsted acid—base reactions. Since the quantity h0 is empirically determined and cannot be broken down experimentally into its component parts, it makes little difference in practice which derivation is used. For direct measurements of hydrogen ion activity coefficients in these solvents, see T. A. Modro, K. Yates, and J. Janata, J. Amer. Chem. Soc., 97, 1492 (1975). 

Therefore one, or a combination, of the following measures can be used to increase the amount to be transferred per unit time (1) Enhancing driving force (2) Increasing interface area and (3) Reducing specific resistance. All three measures are, of course, effective in principle. However, their potential to enhance transfer and the degree of difficulty in carrying them out are quite different in practice. 

The position of ZPD (Zero Path Difference) is critical to the Fourier Transform calculation, since the algorithm assumes that the central burst in the interferogram is in fact the ZPD. However, due to the refractive index properties of the beamsplitter material, the ZPD is not at the same position for every wavelength measured. There are several ways to overcome these phase differences. The most common method is to use a correction factor, which is known as phase correction. This correction factor is calculated for every wavelength, based on a double sided interferogram, since this tends to minimize the effects of phase difference. In practice, most infrared spectrometers collect single sided interferograms, since this halves the mirror movement, and consequently the number of datapoints to be Fourier transformed. 

Therefore, sugar was added to make up for the deficiency. Water, to reduce the high acidity, also was used commonly. The water also reduced the foxy flavor of the native varieties. Neither practice was necessary with V. vinifera varieties in California. Later in the nineteenth century, Eastern bottlers often blended California and Eastern wine. This reduced the strong labrusca and scuppernong flavors and, of course, reduced commercial rivalry. Later, laws permitted use of sugar and water except in California. This difference in practice still exists. 

Turner, Stephen, 2000, What are disciplines And how is interdisciplinarity different In Practicing Interdisciplinarity, edited by Peter Weingart and Nico Stehr, 46-65, Toronto University of Toronto Press,... 

Techniques and plants for polymerization have become more precise and specific but there is a possibility still that similar grades of the same material made in different units may differ in practice (in features such as the distribution of molecular weights, and colour). It will be appreciated too that many polymers and copolymers are used in combination with other substances— stabilizers, fillers, and miscellaneous additives—all of which (and especially those occurring naturally, like China clay and some types of plasticizer) may themselves differ appreciably from batch to batch. 

Now the quinolone synthesis can be executed with the same reagents we used before and all that remains is ester hydrolysis and alkylation at nitrogen. Notice that the quinolone cyclization could in theory have occurred in two ways as the two positions ortho to the amino group are different. In practice cyclization occurs away from the pyridine ring as the alternative quinolone would be impossibly crowded. 

This intense sweetener (8) is quoted as having the same effective sweetness as aspartame, but unlike aspartame it is sufficiently heat stable that it can be added at the beginning of the boil in high-boiled products. If a product with the same amount of acesulfame K is compared with one based on aspartame the taste will be different. In practice acesulfame K is not normally used on its own but is sometimes used with aspartame. Chemically, acesulfame K is the potassium salt of 6-methyl-l,2,3-oxathiazine-4(3//)-one-2,2 dioxide or 3,4-dihydro-6-methyl-l,2,3-oxathiazine-4-one 2,2-dioxide. It can be regarded as a derivative of acetoacetic acid. The empirical formula is C4H4N04KS and its molecular weight is 201.2. 

In 2D TLC, any spot can be defined by a pair of x and y coordinates the quality of a separation can be established by comparing the distance between all pairs of spots in the chromatogram. High resolution will be obtained when the selectivity between the two directions will be significantly different. In practice, several methods have been used to achieve this purpose. The potential methods for obtaining two different separation mechanisms in orthogonal directions are the following ... 

British and American cooperation has reduced to some extent differences in practice in these two English-speaking countries. The British have adopted many of the CA practices, including alphabetic order of prefixes. One of the differences has been in the use of italicized prefixes. The British have italicized many more prefixes than have the Americans. This means a different placement of such names in indexes, since italicized prefixes are not considered in alphabetizing. American and British cooperation has been extended and some of these differences have been eliminated. Thus the British no longer italicize bicyclo-, cyclo-, epi-, iso-, seco-, and spiro- (17). 

This defines a set of equations for the mean field Hamiltonians HPF. These equations have to be solved self-consistently since the thermodynamic values within the angle brackets in (109) involve the mean field Hamiltonians // F. In principle, all // F can be different in practice, we impose symmetry relations. Therefore, we choose a unit cell, compatible with the symmetry of the lattice introduced in Section II,D, and we put Hpf equal to // F whenever P and P belong to the same sublattice. Moreover, we apply unit cell symmetry that relates the mean field Hamiltonians on different sublattices. By using the symmetry-adapted functions introduced in Section II,B, the latter symmetry can be imposed as follows. We select a set of molecules constituting the asymmetric part of the unit cell. Then we assign to all other molecules P Euler angles tip-through which the mean field. Hamiltonian of some molecule P in the asymmetric part has to be rotated in order to obtain HrF. As a result, we... 

The technology proposed by Inventa is similar in principle to that of BASF, but it differs in practice in the type of material used in the unit (plastic instead of stainless steel), and in the choice of the catalyst (platinum instead of palladium). 

This problem is in principle the same as that of the structure of the substrate, but there are some differences in practice. In the first place, the acid-base strength of the catalyst is usually measurable by direct means, and a large part of the variations in reaction velocity merely parallel these variations in acid-base strength. In the second place, it is rarely practicable to vary the strength of the catalyst over a very wide range (because of the catalytic effect of the molecules or ions of the solvent). Moreover, most measurements on catalyzed reactions have been confined to a series of very similar catalysts, and little evidence is available as to how far catalysts of widely differing structure conform to a single Bronsted relation. 

The measurement techniques used at high pressure are similar in principle to tho.se used at low pressure, but different in practice since leakproof metal tubing, fittings, and equilibrium cells (frequently with sapphire windows to enable one to see inside the cell) are used. Also, circulation of the vapor, liquid, or both to ensure that there is good contact between the phases and that equilibrium is obtained is usually done by pumps, rather than by heating to promote boiling, as is the case at low pressures. One example of a high-pressure dynamic VLE cell is shown in Fig. 10.3-4. 

This equation can also be used, with minor differences in practice, for nonideal gases. 

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