Suppression of stimulated Brillouin scattering in optical fibers using a linearly chirped diode laser.

The output of high power fiber amplifiers is typically limited by stimulated Brillouin scattering (SBS). An analysis of SBS with a chirped pump laser indicates that a chirp of 2.5 × 10(15) Hz/s could raise, by an order of magnitude, the SBS threshold of a 20-m fiber. A diode laser with a constant output power and a linear chirp of 5 × 10(15) Hz/s has been previously demonstrated. In a low-power proof-of-concept experiment, the threshold for SBS in a 6-km fiber is increased by a factor of 100 with a chirp of 5 × 10(14) Hz/s. A linear chirp will enable straightforward coherent combination of multiple fiber amplifiers, with electronic compensation of path length differences on the order of 0.2 m.

Genetics of qualitative traits in domesticated chia (Salvia hispanica L.).

In Salvia hispanica L., several changes in qualitative characters, including seed coat color, stem pigmentation, and shattering, have evolved with cultivation and domestication. Three F(2) segregating generations from crosses between wild and domesticated parents were scored for three qualitative traits. A single recessive gene, designated scc, was found to govern the white seed characteristic. A single dominant gene, designated SSP, was found to control striated stem pigmentation. A complete dominance of open calyx over closed calyx was observed in F(1) generations and small numbers of plants with closed calyxes were observed in F(2) generations, not conforming to Mendelian ratios. For this non-shattering trait, a complementation test was conducted between two lines representative of geographically and morphologically divergent domesticated varieties. Complementary gene action was not observed in any F(1) plants, and all F(2) plants were homogeneous with respect to the trait, suggesting the same genetic control for non-shattering among domesticated varieties. An analysis of limited data for linkage of SSP and scc indicated that the two loci segregate independently.

Malignant melanoma of the gallbladder. Report of a case.

A case of malignant melanoma in a 31-year-old man is described to add to the eight cases previously reported in the literature. The tumor in this case shares many common gross and microscopic features with those previously reported. These similarities, in addition to the clinical absence of any primary melanoma in the more common site of occurrence, indicate that the tumor in this case is primary in the gallbladder.