Draw ration

Fig. 3a. P200 and P400 as a function of draw ration for the pseudo-affine deformation scheme (uniaxially oriented sample) b P20o and P400 as a function of draw ratio X for the rubber network affine deformation scheme (N = 6, uniaxially oriented sample). Reproduced from Journal of Polymer Science by permission of the publishers, John Wiley Sons Incs (C)...

The longest Ti c of each sample increase with the increases in draw ration. However, even for 150 fold drawn sample (E) the Tic does not exceed 1650 s. This seems to reflect the phase structure of this type of sample. In addition to the orthorhombic crystalline resonance at 32.9 ppm, the existence of downfield resonance at 34.7-34.8 ppm assignable to the monoclinic crystalline component for all samples was confirmed by examining the relaxation phenomena. 

Caffrey and Bilderback have made a similar study for natural rubber. Using a Vidicon camera they concluded that the amorphous halo disappears while the preferentially oriented powder pattern appears at the same time. Holl et all., have studied the reversibility of this process in more detail. Thus in Fig. 51 the variation of the modulus and the draw ration are compared with selected Vidicon patterns. corresponds to the onset of the crystallization, 3- to the maximum in crystallisation and 3-i to the melting of the last crystallites upon relaxation. Note that and Xj, occurr, at different draw ratios. This is obviously due to the nucleation process which demands a certain overdrawing while the melting occurs at the equilibrium melting temperature. 

V = 0.5 [3] contradict each other (see the Eq. (1.9)). In Refs. [7-9], the relationship was obtained, coupling conditional stress o and draw ration A, at uniaxial tension (compression) of elastomaterials within the frameworks of fractal analysis ... 

Figure 33.11 Draw ration (BUR) effect on bottle shrinkage on heating.

Structural drawings of carbohydrates of this type are called Haworth formulas, after the British chemist Sir Walter Norman Haworth (St Andrew s University and the University of Birmingham) Early m his career Haworth contributed to the discovery that carbohydrates exist as cyclic hemiacetals rather than m open chain forms Later he col laborated on an efficient synthesis of vitamin C from carbohydrate precursors This was the first chemical synthesis of a vitamin and provided an inexpensive route to its prepa ration on a commercial scale Haworth was a corecipient of the Nobel Prize for chem istry m 1937... 

Draw Lewis structures for methyl anion, ammonia and hydronium cation. How many electrons are left over in each after all bonds have been made Display and compare electron density surfaces for methyl anion, ammonia and hydronium cation. Which is the smallest molecule Which is the largest Rationalize your observation. (Hint Compare the number of electrons in each molecule, and the nuclear charge on the central atom in each molecule.)... 

Display and examine electrostatic potential maps for ethyl cation, 2-propyl cation and 2-methyl-2-propyl cation. Which cation shows the greatest localization of positive charge If you find that the methyl groups delocalize the positive charge, where does the charge go Write resonance contributors for the three cations to rationalize your conclusion. (Note You may need to draw resonance contributors that contain a CC double bond and are missing a CH bond see also Chapter 7, Problem 8.)... 

Which of the two enolates enolate A or enolate B) is lower in energy Rationalize your observation by comparing their structures, charge distributions and electrostatic potential maps. Draw all of the resonance contributors needed to describe each enolate. Which enolate is generated by reaction with NaH ... 

Onto which atoms (carbon, nitrogen or both) is the unpaired electron in tricyanomethyl radical delocalized Rationalize your result by drawing resonance contributors. 

Much effort has been expanded in drawing mechanistic inferences from the observation that cofacial bismetalloporphyrins containing a non-redox-active metal ion are fairly selective catalysts (e.g., (DPA)CoM, where M = Lu, Sc, Al, Ag, Pd, 2H, i.e., monometallic porphyrins Fig. 18.15). At least two hypotheses have been proposed (i) polarization of the 0-0 bond in catalytic intermediates by the second ion (on an N-H moiety) acting as a Lewis acid [CoUman et al., 1987, 1994] and (ii) spatial positioning of H+ donors especially favorable for proton transfer to the terminal O atoms of coordinated O2 [Ni et al., 1987 Rosenthal and Nocera, 2007]. To the best of my knowledge, neither hypothesis has yet been convincingly proven nor resulted in improved ORR catalysts. When seeking stereoelectronic rational of the observed av values, it is useful to be mindful that a fair number of simple Co porphyrins are also relatively selective ORR catalysts (Section 18.4.2). 

Usually, the composition of the compound is fulfilled in all of the hexagonal layers. This facilitates a rational classification of the extensive data it is only necessary to draw a sketch of the atomic arrangement in one layer and to specify the stacking sequence... 

Results are not easily rationalized. On one hand, the trend of the product s stereochemistry is comparable with that observed over Cu/Si02, but the reaction rate seems to depend on the steric hindrance of the donor. Moreover, as already mentioned, MgO play a significant role in this reaction. Such observations make it impossible to draw any conclusion about the mechanism. 

This leads to a value of 129° for the ONO bond angle, which may be compared v-ith the accepted value of 134° for free NO2. The smaller bond angle for the adsorbed molecule may be rationalized by assuming that the surface draws the unpaired electron out of the p orbital. 

The Monowitz inmates worked only at double pace, from morning to night. "When the inmates were counted, the living would hold up the dead for counting purposes so they could continue to draw their rations."... 

We underline these results and the implied concepts quoting from a comprehensive review on this subject (Simon 1983). We remember indeed that, ever since it was experimentally possible to determine atomic distances in molecules and crystals, efforts have been made to draw conclusions about the nature of the chemical bonding, and to compare interatomic distances (dimensions) in the compounds with those in the chemical elements. Distances between atoms in an element can be measured with high precision. As such, however, they cannot be simply used in predicting interatomic distances in the compounds. In a rational procedure, reference values (atomic radii) have to be extracted from the individual (interatomic distances) measured values. Various functions have been suggested for this purpose. In the specific case of the metals it has been pointed out that interatomic distances depend primarily on the number of ligands and on the number of valence electrons of the atoms (Pearson 1972). 

Delocalization of charge in the conjugate base anion through resonance is a stabilizing factor and will be reflected by an increase in acidity. Drawing resonance structures allows us to rationalize that the negative charge is not permanently localized on a particular atom, but may be dispersed to other areas of the structure. We should appreciate that a better interpretation is that the electrons are contained in a molecular orbital that spans several atoms. 

Along the same lines, a European Union initiative began last year (2006) to draw up common standards on HTA methods, which can increasingly make or break a new drug, even if it primarily addresses only the question of reimbursement by public health insurance. The hope is to bring greater rationality and speed to a process also known as the fourth hurdle for treatments to win approval, after safety, efficacy, and quality. 

The chemistry of the 2,5-anhydrides of aldoses subsequently entered a prolonged lull, and Peat s review21 of 1946 in this Series does not report on any work later than 1925. The experimental basis of the deamination of amino sugars with nitrous acid was, nevertheless, established. The progress afterwards made in the conformational analysis of sugars made it possible for Shafizadeh22 to draw a parallel with the nitrous acid deamination of the aminocyclohexanols, and to rationalize the whole of these results. 

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