Cd Mole Fraction Research Articles

Optically pumped laser oscillation at ≊2.9 μm of a HgCdTe layer grown by metalorganic chemical vapor deposition

Photopumped pulsed stimulated emission at 2.9 μm in a HgCdTe layer grown by metalorganic chemical vapor deposition on a CdTe substrate was studied as a function of temperature. The threshold power of the HgCdTe laser (photoexcited by a GaAs diode laser) increased from 0.04 W at 12 K to 1.58 W at 150 K. Above 50 K, the temperature dependence of the threshold is exponential, yielding a T0 of 31 K. From the observed laser emission wavelength a Cd mole fraction of x=0.422 was determined. The far-field angular full width at e−2 of peak intensity was 5.5° and 9.5° perpendicular and parallel to the film plane, respectively.

A kinetic model for colchicine inhibition of microtubule assembly

Colchicine is a potent drug used to probe microtubule dependent processes. We have recently shown that substoichiometric concentrations of colchicine-tubulin complex (CD), a 1:1 tight binding complex of drug with tubulin, copolymerizes with tubulin to form microtubule copolymers. The affinity of the microtubule ends for tublin decreased as the CD mole fraction in the microtubule increased. Mole fraction ratios as small as 1 CD to approx. 50 to 100 tubulins in the copolymers were accompanied by a significant change in binding affinities and polymerization rates. We have further extended our investigation of the CD-tubulin copolymerization reaction. A kinetic model was derived which relates the composition of the microtubule copolymer to the composition of the reaction mixture. This model allowed a predictive correlation to be made between copolymer composition and the extent of assembly inhibition.