Structures of flavone and flavonol glycosides
SummaryLiterature information on the structures of O-glycosides of flavones and flavonols has been generalized. Using the methods of combinatorial mathematics, the possibility of a great diversity of the structure of the glycosides has been shown without taking into account their acylation, the dimensions of the oxide rings of the sugars, and the nature of the glycosidic bonds.
A Study of Trillium cuneatum and T. luteum
A systematic study was made of two taxa of the genus Trillium subgenus Phyllantherum. }'rorphologi cal, biochemical, ecological, and distributional data were analyzed in order to reevaluate past taxonomic treatments of Trillium cuneatum and T. luteum. Morphological studies revealed the similarities of the two taxa. It was noted that T. cuneatum exhibited great plasticity with respect to morphology, whereas T. luteum shO"tled more homogeneous features. This same relationship was noted with the flavonoids of the two taxa with T. cuneatum showing more variability than T. luteum. The chemistry of the two taxa was unique in that quercetin and kaempferol compounds identified portrayed significant glycoside diversity. A survey of past literature dealing with similar phenolic compounds resulted in an elucidation of the color variation seen ~"i thin allopatric populations of T. cuneatum and led to a belief that T. luteum originally evolved from T. cuneatum as a homozygous recessive form which was favored due to more efficient sexual reproduction accompanying apomictic reproduction. Scanning electron micrographs revealed different types of pollen grains which appeared to have taxonomic significance. The abaxial surfaces of the bracts apparently iii were identical. Photom:icrographs were useful also in revealing spiders as possible pollinating agents within the genus. Predator--prey relationships and cryp tic coloring are discussed as possible factors affecting reproductive success of the plants. iv Recent taxonomic treatments were reviewed and possible taxonomic considerations were considered. Based on the results of this study and past work of other botanis ts, it was concluded that the two taxa should be recognized as distinct spocies in keeping with traditional tre a t~ents. It is believed that the two taxi represent a good case of directional selection resulting in divergent evolution . Whether this divergence will result in more speci Rtion in the future or whether the two taxa l.~ill merge into a single unit via introgressive hybridization, is a stimulating academic consideration.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME