Primary structure parameters

The diffusion coefficient extrapolated to C2 = 0 can be related to a primary structural parameter, the Stokes radius Rg through the equation ... 

The determination of the absolute average molecular weight, which refers to the primary structure parameters, should be discussed first, because it is mainly responsible for the viscoelastic flow phenomena observed with polymer solutions in shear and elongational flow The absolute average molecular weight may be determined, either by light scattering (M ) or by osmotic pressure measurements It is a fact, that with... 

Here a spinodal decomposition can be initiated by a temperature jump into an upper miscibility gap. Similarity implies that in a representation with reduced variables, plotting log(///max) versus log q/qm3.x), curves measured at different times must become identical. As we can see, this is indeed true. We notice in addition that even the structures observed at different temperatures are similar to each other. We thus have a most simple situation that allows us to describe the kinetics of unmixing by the time dependence of just one parameter. Possible choices are either representing a typical length in the structure, or the interfacial area per unit volume, denoted by O12. In fact, both quantities are related. Two-phase systems in general have two primary structure parameters, namely the volume fraction of one phase, , and O12. As explained in Sect. A.4.2 in the Appendix, from 4> and O12 one can derive a characteristic length of the structure, Ic, as... 

To characterize the supermolecular structure of cellulose, the primary structural parameters (type of crystalline allomorph, crystallinity, paracrystallinity and amorphicity, and orientation of nanofibrils, nanocrystallites, and nanoscale non-crystalline domains, as well as porosity of cellulose) should be determined. These structural parameters can affect physicochemical, chemical, biochemical, physical and mechanical properties of cellulose materials. 

In this Chapter, the structure and properties of cellulose materials are discussed furthermore, in order to predict the cellulose properties, their dependence on the primary structural parameters is described. 

The primary structural parameters such as crystallinity, paracrystallinity, amorphicity, MFA, specific surface and porosity should be determined to characterize the supermolecular structure of cellulose. These structural parameters affect various physical, physicochemical, chemical and biochemical properties of cellulose materials. 

The molecular structure and properties of polyolefins have been explained by several workers in the past [10-14]. This chapter deals with the primary molecular parameters and their effect on processability and ultimate properties of PEs. Since molecular parameters are closely interrelated, it is not possible to discuss one without referring to the other. Hence, in the section relating to the effect of chain branching, reference has also been made to MW and MWD and vice versa. 

The cross-section of the primary X-ray beam is extended and not an ideal point. This fact results in a blurring of the recorded scattering pattern. By keeping the cross-section tiny, modern equipment is close to the point-focus collimation approximation - because, in general, the features of the scattering patterns are relatively broad. Care must be taken, if narrow peaks like equatorial streaks (cf. p. 166) are observed and discussed. The solution is either to desmear the scattering pattern or to correct the determined structure parameters for the integral breadth of the beam profile (Sect. 9.7). 

The rather time- and cost-expensive preparation of primary brain microvessel endothelial cells, as well as the limited number of experiments which can be performed with intact brain capillaries, has led to an attempt to predict the blood-brain barrier permeability of new chemical entities in silico. Artificial neural networks have been developed to predict the ratios of the steady-state concentrations of drugs in the brain to those of the blood from their structural parameters [117, 118]. A summary of the current efforts is given in Chap. 25. Quantitative structure-property relationship models based on in vivo blood-brain permeation data and systematic variable selection methods led to success rates of prediction of over 80% for barrier permeant and nonper-meant compounds, thus offering a tool for virtual screening of substances of interest [119]. 

The rates of formation of various cyclic peptides and DKPs have been documented and shown to be affected by a wide range of physicochemical and structural parameters. Goolcharran and Borchardt examined the effects of exogenous (i.e., pH, temperature, buffer species, and concentration) and endogenous (i.e., primary sequences) factors affecting the rate of cyclic dipeptide formation, using the dipeptide analogues of X-Pro-/)-nitroaniline (X-Pro-/>NA where X represents the amino acid residue of the respective cyclic dipeptide). 

Most of the unknown structures is determined from single crystal diffraction and refined from powder diffraction. Refinement is done with the Rietveld method, which is a least square fitting of the computed pattern to the measured one, while structure parameters are treated as the primary fitting parameters. This is in contrast to the procedure in pattern decomposition, which is outlined above (where not the structure parameters, but the peak intensities were the primary fitting parameters). Beside the... 

Crystalhzation is another typical example of self-organization. The form of the crystal lattice, say of crystallizing NaCl, is not imposed by external forces, but is the result of the internal structural parameters of the NaCl system under the given conditions (temperature, etc.). Protein folding is also a self-organization process, determined by the internal rules of the system (primarily the primary structure). As is well known, Chris Anhnsen and coworkers demonstrated in the 1970s that... 

An interesting aspect of many structural phase transitions is the coupling of the primary order parameter to a secondary order parameter. In transitions of molecular crystals, the order parameter is coupled with reorientational or libration modes. In Jahn-Teller as well as ferroelastic transitions, an optical phonon or an electronic excitation is coupled with strain (acoustic phonon). In antiferrodistortive transitions, a zone-boundary phonon (primary order parameter) can induce spontaneous polarization (secondary order parameter). Magnetic resonance and vibrational spectroscopic methods provide valuable information on static as well as dynamic processes occurring during a transition (Owens et ai, 1979 Iqbal Owens, 1984 Rao, 1993). Complementary information is provided by diffraction methods. 

In many instances, the linkage oligosaccharide is associated with a peptide moiety, and thus the amino acid sequence must be established and, in addition, the structural parameters of the CPL oligosaccharide determined. The latter comprise (i) primary structure, (i i) type and location of noncarbohydrate substituents, and (i i i) the linkage to the peptide backbone. For gaining insight into structure-function relations, it is important for the three-dimensional structure to be determined. 

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