Dissymmetry constant

The ratio Do/D is known as the dissymmetry constant or the frictional ratiOy and is a measure of the extent to which the molecule deviates from a perfect sphere. 

The enzyme ribonuclease has a dissymmetry constant of 1.04 thus the molecule is nearly spherical Tobacco mosaic virus, on the other hand, has a DoJD value of 3.12, and is cigar-shaped. If a molecule is assumed to have the shape of an ellipsoid, the ratio of the major and minor axes can be calculated from the dissymmetry constant. 

In 1964, Cahn, Ingold, and Prelog (see p. 130) proposed that chemists use the terms chiral and chirality as defined by Kelvin. Based on the Greek word for hand (cheir), chirality means handedness, in reference to that pair of non-supcrimposablc mirror images we constantly-have before us our two hands. There has been wide-spread acceptance of Kelvin s terms, and they have largely displaced the earlier dissymmetric and dissymmetry (and the still earlier—and less accurate— asymmetric and asymmetry ), although one must expect to encounter the older terms in the older chemical literature. 

The above-mentioned method was initially developed for measuring the isobaric heat capacities of aqueous salt solutions up to 573 K and 30 MPa. For a typical run, the sample cell was loaded with the sample solution and the reference cell was loaded with a reference fluid of known heat capacity (usually water). Then, the temperature was increased from to T, at constant pressure, and the difference Q in the transferred heat was corrected taking into account both the cell s volumetric dissymmetry and the differences between the densities and specific heat capacities of the measured sample and reference fluids, respectively. Such an experiment allows the measurement of the product pCp representing the isobaric heat capacity divided by volume. In order to obtain the desired isobaric heat capacity, Cp, of the solution, it was necessary to know its density. For this purpose, the isobaric specific heat capacity and density were represented by polynomials in terms of temperature T ... 

The dissymmetry of space-time is one of the basic features indicating the dynamic characteristics of living natural bodies. We could, for example, ask ourselves, whether the leaves of a lime-tree dried for a herbarium are living natural bodies The following could be an approximate answer although the pressed leaves manifest static space dissymmetry on the micro- and macrolevel they demonstrate no dynamic dissymmetry. Dissymmetry is a constant choice of the organism, a permanent process in the scale of the whole biosphere. The bilateral biocontrolled flow of atoms does not take place in this case because there is no dynamically filled boundary between the space-time of the pressed leaves and the space-time of the enviromnent , J)eath is the destruction of the space-time of the organism (Vernadsky, 1988, p. 285). 

We can also say that the dissymmetry principle is correct if the transition from a dissjonmetrical space-time to a symmetrical one is impossible without the loss of its own identity (substantial characteristic). However, such a transition from a dissymmetrical state of space-time into a space-time of the inert environment can be, according to Vernadsky, constantly observed. It is death. The transition from a symmetrical state of space-time to a dissymmetrical state of space-time is impossible. 

The Pfeiffer effect, the outer-sphere interaction of a chiral substrate with a rapidly interconverting racemic solution of a chiral lanthanide complex, can be investigated by measurement of the luminescence dissymmetry factor (the ratio of circularly polarized luminescence to total luminescence) for Eu or Tb " complexes. Thus the racemic D chiral complexes [M(dpa)3], where M = Eu or Tb, interact in an outer-sphere manner with the following optically active spiecies cationic chiral transition metal complexes, ascorbic acid, aminocarboxylates, tartrates, amines and phenols. Association constants can be obtained from limiting values of the dissymmetry factors. In some cases, inner-sphere complexation can be demonstrated, as judged by changes in the general nature of the circularly polarized luminescence spectrum and pH irreversibility of the complexation. 

It can be stated with reasonable assurance that the particle content is conserved in the process though the dissymmetry of the density profile in the blobs renders any Abel inversion strictly speaking unpracticable. Relaxation sets in, in pinch discharges, provided there is a small dissipative mechanism related to some level of microscopic activity. Then lines of force can break and rejoin on a time scale close to the resistive diffusion time. It is widely accepted that such states evolve towards a minimum energy state which obeys a force-free configuration in which V X -B = (jl-B with (ji a constant for all field lines, and B is the magnetic field. 

Minoura and co-workers [28], in contrast with previous expressions for degradation (see Section II.C), found that the reaction rate constant k increases and decreases with decreasing They attributed this discrepancy to a dissymmetry in the initial MWD for the poly(ethylene oxide). 

The feasibility of Kj determinations in the context of one-atom-at-a-time chemistry is very promising and the collection of Kj values will allow establishment of reliable variations of the chemical properties (complexation, hydrolysis) of elements within a group, for comparison with theoretical predictions, and, perhaps, for determination of thermodynamic constants. Moreover, other information can be derived from chromatography experiments. The mathematical treatment of elution curves can be carried out with various models, especially Glueckauf s, which offers the advantages of using simple equations and takes into account the possible dissymmetry of elution bands [31, 32]. The parameters included in Glueckauf s equations allow the determination of the distribution... 

The interpretation of turbidities in the absence of angular dissymmetry was developed by Stockmayer from the fluctuation of the refractive index in multicomponent systems. The turbidity t of a solution of C component at constant T and P is given by the equation... 

The equilibrium constants and the dissymmetry factors are very similar but the stoichiometry is very different. For further details see ref. [59]. 

Measurement of CPL from racemic mixtures is not a technique that can be applied to all racemic solutions. For moderately luminescence systems values of approximately 10 are measurable. This means that the intrinsic absorption and emission dissymmetry ratios need to be on the order of 10 for this experiment to be successful. Although there have been a couple of examples using this technique in organic systems, by far the most widely studied systems are racemic lanthanide complexes, such as given in Figure 5, because of the large and g bs values that may exist for certain f o f transitions. It is also useful to perform these experiments in a time-resolved mode and as a function of temperature to determine racemization rate constants. 

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