RESUMO
HgCdTe is promising as a material to solve a problem of the development of semiconductor sources with an operational frequency range of 6-10â THz due to the small optical phonon energies and electron effective mass. In this study, we calculate the dependence of the metal-metal waveguide characteristics on the number of cascades for the 3-well design HgCdTe-based quantum cascade laser at 8.3â THz. It is shown that four cascades are sufficient for lasing at a lattice temperature of 80â K due to the large gain in the active medium. The results of this study provide a way to simplify the fabrication of thin active region HgCdTe-based quantum cascade lasers for operation in the range of the GaAs phonon Reststrahlen band inaccessible to existing quantum cascade lasers.
RESUMO
The effect of N-nitroxymethyl succinimide (1), N-(2-nitroxyethyl) succinimide (2) and N-(3-nitroxypropyl) succinimide (3) on enzymatic activity of cyclic guanosine monophosphate (cGMP) phosphodiesterase was studied and crystal structure of compound (2) was determined. It was shown that all studied N-nitroxy succinimides inhibited cGMP phosphodiesterase in a concentration range of 0.1-0.001 mM. Compound (2) noncompetitively and reversibly inhibited hydrolytic function of enzyme with Ki=1.7×10-5 Ð. Inhibition constant for the reference compound N-(2-nitroethyl) nicotinamide (nicorandil) was 3×10-5 Ð.
Assuntos
GMP Cíclico/metabolismo , Guanosina Monofosfato/metabolismo , Diester Fosfórico Hidrolases/metabolismo , Succinimidas/farmacologia , Animais , Ativação Enzimática/efeitos dos fármacos , Cinética , Ratos , Ratos WistarRESUMO
Radiative recombination is studied in CdHgTe/HgTe QWs with bandgap in the 40-140 meV range using four-band Kane model. Calculated radiative lifetimes agree well with the photoconductivity kinetics measurements. We show that the side maxima in the valence band hinder the radiative recombination at high carrier concentrations and discuss how to overcome this effect for the development of long-wavelength lasers.
RESUMO
We report stimulated emission in the 2.8-3.5 µm wavelength range from HgTe/CdHgTe quantum well (QW) heterostructures at temperatures available with thermoelectric cooling. The structures were designed to suppress the Auger recombination by implementing narrow (1.5 - 2 nm wide) QWs. We conclude that Peltier cooled operation is feasible in lasers based on such structures, making them of interest for spectroscopy applications in the atmospheric transparency window from 3 to 5 µm.
RESUMO
The effect of substituted nicotinamides and isonicotinamides and Pt(IV) metal complexes based on the substituted nicotinamides and isonicotinamides on the activity of cAMP phosphodiesterase was studied. Isonicotinamide derivatives are efficient enzyme activators, whereas substituted nicotine amides are inhibitors of enzymatic cAMP phosphodiesterase activity; their inhibitory potency is comparable to that of theophylline used as a reference drug.