Proposal for a phonon laser utilizing quantum-dot spin states.

We propose a nanoscale realization of a phonon laser utilizing phonon-assisted spin flips in quantum dots to amplify sound. Owing to a long spin relaxation time, the device can be operated in a strong pumping regime, in which the population inversion is close to its maximal value allowed under Fermi statistics. In this regime, the threshold for stimulated emission is unaffected by spontaneous spin flips. Considering a nanowire with quantum dots defined along its length, we show that a further improvement arises from confining the phonons to one dimension, and thus reducing the number of phonon modes available for spontaneous emission. Our work calls for the development of nanowire-based, high-finesse phonon resonators.

[Cloning of the flagellate Crithidia oncopelti on a solid nutrient medium of indeterminant composition not containing hemin]. / Klonirovanie zhgutikonostsa Crithidia oncopelti na plotnoi pitatel'noi srede neopredelnnogo sostava, na soderzhashchei gemin.

On a simple solid medium of indefinite content without hemin, colonies of Crithidia oncopelti were received. The clonal nature of them was proved. The survival in some experiments varied from 10 to 70%. Young colonies, 6 days after inoculation, were 0.3- 2.0 mm in diameter. C. oncopelti differed from Herpetomonas megaseliae and Crithidia harmosa in the morphology of colonies. To further genetical study of C. oncopelti, a possibility of cloning the object on a simple solid medium is an important prerequisite.