Surpassing fundamental limits of oscillators using nonlinear resonators.

In its most basic form an oscillator consists of a resonator driven on resonance, through feedback, to create a periodic signal sustained by a static energy source. The generation of a stable frequency, the basic function of oscillators, is typically achieved by increasing the amplitude of motion of the resonator while remaining within its linear, harmonic regime. Contrary to this conventional paradigm, in this Letter we show that by operating the oscillator at special points in the resonator's anharmonic regime we can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit. We develop a comprehensive model that accounts for the major contributions to the phase noise of the nonlinear oscillator. Using a nanoelectromechanical system based oscillator, we experimentally verify the existence of a special region in the operational parameter space that enables suppressing the most significant contributions to the oscillator's phase noise, as predicted by our model.

[Obtaining and rearing germ-free miniature piglets for biomedical research]. / Opyt polucheniia i vyrashchivaniia bezmikrobnykh miniatiurnykh porosiat dlia mediko-biologicheskikh issledovanii.

The method of obtaining and rearing germfree miniature piglets for medical-biological research is described. The gnotobiotes were reared in rigid organic glass isolation cells up to 3 months. Milk diets supplemented with minerals and vitamins were used for nutrition. The gnotobiotes gained weight well during the whole observation period.

[Ultrastructural changes in plague microbes, strain EV, and splenic cells of guinea pigs in their interaction in vitro]. / Ul'trastrukturnye izmeneniia chumnykh mikrobov shtamma EV i kletok selezenki morskikh svinok pri vzaimodeistvii in vitro.

Dilatation of the endoplasmic reticulum cavities, an increase in the number of ribosomes near bacteria, deformation of mitochondria and coarsening of cristae were revealed in phagocytosis of Past. pestis, strain EV, by reticular cells in the tissue culture of the spleen of intact guinea pigs. Lipophanerous "reticular" inclusions were found in the differentiated reticular cells of the infected cultures. In the reticular cell cytoplasma besides the intact bacteria there were revealed Past. pestis at the initial stages of involution.