Antiparallel

Figure A3.5.2. The Ar photofragment energy spectmm for the dissociation of fiions at 752.5 mn. The upper scale gives the kinetic energy release in the centre-of-mass reference frame, both parallel and antiparallel to the ion beam velocity vector in the laboratory.

FIGURE 13 3 (a) In the absence of an external magnetic field the nuclear spins of the protons are randomly oriented (b) In the presence of an external magnetic field Xq the nuclear spins are oriented so that the resulting nuclear magnetic moments are aligned either parallel or antiparallel to Xq The lower energy orientation is the one parallel to Xq and more nuclei have this orientation... 

Among the 76 nucleotides of tRNA are two sets of three that are especially important The first is a group of three bases called the anticodon, which is comple mentary to the mRNA codon for the ammo acid being transferred Table 28 3 lists two mRNA codons for phenylalanine UUU and UUC (reading m the 5 3 direction) Because base pairing requires the mRNA and tRNA to be antiparallel the two anticodons are read m the 3 5 direction as AAA and AAG... 

Singlet states with the same configuration as in Equation (7.59) with antiparallel spins of the electrons in the n 2p orbital are higher in energy and are low-lying excited states. 

This result is similar to that for e x e, in Equation (4.29), in the point group and can be verified using the Tig , character table in Table A.36 in Appendix A. As the two electrons (or one electron and one vacancy) in the partially occupied orbitals may have parallel (S = 0) or antiparallel (5=1) spins there are six states arising from the configuration in Equation... 

The magnetic moments of the heavy RE elements (Gd, Tb, Dy, etc) are coupled antiparallel to the magnetic moments of the TM elements (Fe, Co, etc). The REj TM alloys are therefore ferrimagnetic below their Curie temperature (T )- The heavy TM moments form one magnetic sublattice and the RE moments the other one. In contrast, the light RE moments (eg, Nd, Pr) couple parallel to the moments of TM. The RE spia is always antiparallel to the TM spia, but for the light RE elements, the orbital momentum is coupled antiparallel to the spia and larger than the spia. 

Similar models for the crystal stmcture of Fortisan Cellulose II came from two separate studies despite quite different measured values of the diffraction intensities (66,70). Both studies concluded that the two chains in the unit cell were packed antiparallel. Hydrogen bonding between chains at the corners and the centers of the unit cells, not found in Cellulose I, was proposed to account for the increased stabiUty of Cellulose II. The same model, with... 

Cellulose III. Cellulose III results from treatment of cellulose with Hquid ammonia (ammonia mercerization) or amines. Cellulose III can be made from either Cellulose I or II. When treated with water. Cellulose III can revert to its parent stmcture. Some cellulose III preparations are much more stable than other preparations. The intensities on diffraction patterns from Cellulose III differ slightly depending on whether the Cellulose III was made from Cellulose I or II, and thus these allomorphs are called IIIj or IHjj- Workers studying III concluded, based partiy on the results of I and II, that the packings of IIIj and IIIjj are parallel and antiparallel, respectively (67). IIIjj also is thought to have hydrogen bonds between the corner and center chains. 

A study of the effect of substitution patterns in oxadiazoles and isoxazoles and their effect on the UV spectra in the lO -lO M concentration range was performed. Hypso-chromic effects and deviations from Beer s law were observed and were believed to be associated with antiparallel, sandwich-type self-association via dipole-dipole interactions. Beer s law is followed when the molecular dipole moments are small or when self-association is sterically hindered. 

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