Effects of chromophore dissociation on the optical properties of rare-Earth-doped polymers.

The observed dissociation of tetrakis rare-earth chromophores in rare-earth-doped organic polymers is reported, and a time-resolved spectroscopic technique is presented to determine quantitatively the fractional concentrations of different chromophore species in various solvents. Based on this technique, the equilibrium constants of tetrakis rare-earth chromophores in rare-earth-doped polymers are determined. Thus, the equilibrium constants for tetrakis rare-earth compounds of benzoyltrifluoroacetonate (BTF), for example, Sm(BTF)(4)P and Eu(BTF)(4)P in methyl methacrylate monomer, are K = 4.

Primitive mesenteric gastrointestinal stromal tumor with autonomic nerve/ganglionic differentiation presenting as a huge mass with small synchronous nodules.

We present a case of a primary mesenteric ectopic gastrointestinal stromal tumor. The pathologic characteristics of this neoplasm, autonomic nerve/ganglionic differentiation and presentation as a huge mass with small synchronous nodules, have not been previously described in the literature.

Effects of random perturbations in plastic optical fibers.

REVIEW The most important feature of an optical fiber waveguide is its bandwidth, which defines its information-carrying capacity. A major limitation on the bandwidth of multimode glass and plastic optical fibers is modal dispersion, in which different optical modes propagate at different velocities and the dispersion grows linearly with length. However, in plastic optical fibers, experimental and theoretical results indicate that the modes are not independent but are highly coupled, which leads to a characteristic square-root length dependence and an unanticipated large enhancement of the bandwidth to gigahertz levels.

Room-temperature green upconversion fluorescence of an Er(3+)-doped laser liquid.

Room-temperature green upconversion fluorescence of an Er(3+)-doped POCl(3)-SnCl(4) solution is achieved when the solution is pumped with an 800-nm GaAs laser diode. The upconversion emission at 550 nm is determined to be the result of a two-step absorption process. Numerical analysis reveals that laser systems that employ this erbium-doped laser liquid should be realizable with threshold pump powers as low as 45 mW.