Regular equimodular sets of matrices for generalized matrix functions

Using expansions of generalized matrix functions by means of cyclic products and principal majors, conditions for regularity of equimodular classes of matrices are found.     

Excitation and temperature dependence of the excitonic emissions in undoped and Mg-doped VPE InP

The photoluminescence of vapor phase epitaxial indium phosphide, both unimplanted and magnesium implanted, is investigated as a function of excitation intensity and temperature to gain a more complete understanding of the free exciton, exciton-bound donor, exciton-bound acceptor (residual and Mg), the 1.4155 eV emission identified with both the recombination of free holes with neutral donors and with bound excitons to ionized donors, and the recently identified 1.4122 eV emission (unique to Mg implanted layers). Emission peak broadening, quenching, and saturation is examined as the irradiance is varied from 0.002 to 33.3 W/cm² and the temperature from 2.6 to 50 K. The source of the 1.4122 eV emission is speculated to be a donor-acceptor recombination involving a donor center bond to an off-axis band and the Mg acceptor, or more likely, excitons bound to point defects which are created by the acceptor implant.     

Structural characterization of artificial self-assembling porphyrins that mimic the natural chlorosomal bacteriochlorophylls c, d, and e

We report two crystal structures of a synthetic porphyrin molecule which was programmed for self-assembly. The same groups which ensure that bacteriochlorophylls c, d, and e can self-assemble into the chlorosomal nanorods, the photosynthetic antenna system of some green bacteria, have been engineered into desired positions of the tetrapyrrolic macrocycle. In the case of the 5,15-meso-substituted anchoring groups, depending upon the concentration, by using the same crystallization solvents, either a tetragonal or a layered structure of porphyrin stacks were encountered. Surprisingly, pi-pi interactions combined with extensive dispersive interactions, which also encompass cyclohexane, one of the crystallization solvents, win over putative hydrogen bonding. We are aware that our compounds differ considerably from the natural bacteriochlorophylls, but based upon our findings, we now question the hydrogen-bonding network, previously proposed to organize stacks of bacteriochlorophylls. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS) on various isomeric compounds support our challenge of current models for the chlorosomal antenna as these show structures, astonishingly similar to those of chlorosomes.