Anisotropy positive

The methods diseussed so far, fluoreseenee upeonversion, the various pump-probe speetroseopies, and the polarized variations for the measurement of anisotropy, are essentially eonventional speetroseopies adapted to the femtoseeond regime. At the simplest level of interpretation, the infonnation eontent of these eonventional time-resolved methods pertains to populations in resonantly prepared or probed states. As applied to ehemieal kineties, for most slow reaetions (on the ten pieoseeond and longer time seales), populations adequately speeify the position of the reaetion eoordinate intemiediates and produets show up as time-delayed speetral entities, and assignment of the transient speetra to ehemieal stnietures follows, in most oases, the same prinoiples used in speotrosoopio experiments perfomied with oontinuous wave or nanoseoond pulsed lasers. 

Recent tlieoretical [35, 36 and 37] and experimental [38] research has revealed anomalous behaviour of tire dimer anisotropy under certain excitation conditions. If tire dimer is excited by broadband light tliat covers botli excitonic transitions, or by a relatively narrow band properly positioned between tire maxima of tire excitonic transitions, tire... 

Change of compensation temperature with composition is Positive value of K indicates perpendicular anisotropy. 

Mechanical Properties and Structural Performance. As a result of the manufacturing process, some cellular plastics have an elongated cell shape and thus exhibit anisotropy in mechanical, thermal, and expansion properties (35,36). Efforts are underway to develop manufacturing techniques that reduce such anisotropy and its effects. In general, higher strengths occur for the paraHel-to-rise direction than in the perpendicular-to-rise orientation. Properties of these materials show variabiUty due to specimen form and position in the bulk material and to uncertainty in the axes with respect to direction of foam rise. Expanded and molded bead products exhibit Httie anisotropy. 

Representative chemical shifts from the large amount of available data on isothiazoles are included in Table 4. The chemical shifts of the ring hydrogens depend on electron density, ring currents and substituent anisotropies, and substituent effects can usually be predicted, at least qualitatively, by comparison with other aromatic systems. The resonance of H(5) is usually at a lower field than that of H(3) but in some cases this order is reversed. As is discussed later (Section 4.17.3.4) the chemical shift of H(5) is more sensitive to substitution in the 4-position than is that of H(3), and it is also worth noting that the resonance of H(5) is shifted downfield (typically 0.5 p.p.m.) when DMSO is used as solvent, a reflection of the ability of this hydrogen atom to interact with proton acceptors. This matter is discussed again in Section 4.17.3.7. 

In the following development we consider a plane wave of infinite lateral extent traveling in the positive Xj direction (the wave front itself lies in the Xj, Xj plane). When discussing anisotropic materials we restrict discussion to those propagation directions which produce longitudinal particle motion only i.e., if u is the particle velocity, then Uj = Uj = 0. The <100>, <110>, and <111 > direction in cubic crystals have this property, for example. The derivations presented here are heuristic with emphasis on the essential qualitative features of plastic flow. References are provided for those interested in proper quantitative features of crystal anisotropy and nonlinear thermoelasticity. 

Anisotropy of molecular motion monosubstituted benzene rings, e.g. phenyl benzoate (44), show a very typical characteristic in the para position to the substituents the CH nuclei relax considerably more rapidly than in the ortho and meta positions. The reason for this is the anisotropy... 

Compound 68 can also be obtained by an acid-catalyzed cyclization of 42, which was prepared by the Michael addition reaction of 39 to mesityl oxide as shown in Section IV.A. As for the product 69, the presence of the tosyloxy group at the 5 position instead of the 6 position is determined, utilizing the anisotropy effect of the 1-acetyl group to the C-7 proton, by comparing its H NMR spectrum with that of 70, obtained in 69% yield by the treatment of 69 with NaH and AcCl. 

From the NMR data of the polymers and low-molecular models, it was inferred that the central C—H carbons in the aliphatic chain in polymer A undergo motions which do not involve the OCH2 carbons to a great extent. At ambiet temperatures, the chemical shift anisotropy of the 0(CH2)4 carbons of polymer A are partially averaged by molecular motion and move between lattice positions at a rate which is fast compared to the methylene chemical shift interaction. 

Kashiwagi et al.10) determined the second moment anisotropy for the one-way drawn polyethylene terephthalate sheets discussed above. The three lattice sums S00, S2q and S4o were calculated from the crystal structure determination of Daubeny et al., the proton positions being calculated on the basis of known bond angles and lengths. The isotropic lattice sum S00 was adjusted to a value consistent with the measured isotropic second moment of 10.3G2. The values for P200, P220 etc. were then used to predict the optical anisotropy. The predicted refractive indices for the sheets of draw ratio 2 1 and 2.5 1 are shown in Fig. 10, together with the experimental... 

Liquid crystals form a state of matter intermediate between the ordered solid and the disordered liquid. These intermediate phases are called mesophases. In the crystalline state the constituent molecules or ions are ordered in position and orientation, whereas in the liquid state the molecules possess no positional and orientational ordering. Liquid crystals combine to some extent the properties of both the crystalline state (optical and electrical anisotropy) and the liquid state (fluidity). 

The chemical shifts of the H-methyl groups in thiiranes 31a, 31b and 31c were found to be = 1.59,1.44 and 1.45, respectively. The chemical shifts of the -anti-methyl hydrogens (i.e. those of R ) where found to be (5 = 1.25,1.23 and 1.27 in 32a-c compared with <5= 1.74 and 1.64 for syn-R -hydrogens in 32a and 31c, respectively . The consistency of the deshielding effect in accordance with the position of the -hydrogens in ring sulfoxides is thus apparent. These observations validate the applicability of the S—O anisotropy rule to the three-membered ring system. 

In contrast, soft magnetic solids and paramagnetic systems with weak anisotropy may be completely polarized by an applied field, that is, the effective field at the Mossbauer nucleus is along the direction of the applied field, whereas the EFG is powder-distributed as in the case of crystallites or molecules. In this case, first-order quadrupole shifts cannot be observed in the magnetic Mossbauer spectra because they are symmetrically smeared out around the unperturbed positions of hyperfine fines, as given by the powder average of EQ mj, d, in (4.51). The result is a symmetric broadening of all hyperfine fines (however, distinct asymmetries arise if the first-order condition is violated). 

One can clearly see the large positive anisotropy in the [111] direction near the boundary of the first Brillouin zone (BZB). It is caused by the [111] high momentum component, which produces a continuous distribution of the momentum density across the BZB, as the Fermi surface has contact with the BZB in this direction. In the other directions, especially in [100], calculations show a steep decrease of the momentum density at the Fermi momentum and therefore a negative deviation from the spherical mean value. 

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