RESUMO
The electrical response of a two-dimensional electron gas to vibrations of a nanomechanical cantilever containing it is studied. Vibrations of perpendicularly oriented cantilevers are experimentally shown to oppositely change the conductivity near their bases. This indicates the piezoelectric nature of electromechanical coupling. A physical model is developed, which quantitatively explains the experiment. It shows that the main origin of the conductivity change is a rapid change in the mechanical stress on the boundary between suspended and nonsuspended areas, rather than the stress itself.
RESUMO
The resistance R of the 2DEG on the vicinal Si surface shows unusual behavior which is very different from that in Si (100) MOSFET's studied earlier. The low-temperature crossover from dR/dT<0 ("insulator") to dR/dT>0 ("metal") occurs at a low resistance of R(c)square approximately 0.04xh/e2. This crossover, which we attribute to the existence of a narrow impurity band at the interface, is accompanied by a distinct hysteresis in the resistance. At higher temperatures, another change in the sign of dR/dT is seen. We describe it by temperature dependent impurity scattering of the 2DEG near the transition from the degenerate to nondegenerate state.
RESUMO
Experiments were made on 26-month-old piglets divided into 4 groups: Groups 1 and 4 included 5 piglets and Groups 2 and 3 comprised 8 animals. The piglets from Groups 1, 2, and 3 were peritoneally inoculated with 5000 protoscolices and acephalocysts of Echinococcus from patients with echinococcosis who had been operated on. On postinoculation day 60, Group 1 piglets were killed to measure the baseline weight of parasitic larvocysts (PL) developed by that time. On postinoculation day 61, Group 3 piglets continuously received feed in combination with CK-1 within 3 weeks. The mean daily doses of the agent were 0.05, 0.10, 0.25 g/kg, respectively. On day 91 following inoculation, all the animals were killed and dissected. The studies were made by using the procedures and formulas [9]. The growth suppression index for PL was 94.50, 92.39, and 96 for Groups 1, 2, and 3, respectively. Significant destruction of embryonic elements was revealed in 75-85% of PL in each treated animals. There was a tendency for blood indices to become normal in the treated animals. The acute toxicity of CK-1 was examined in outbred white mice, albino rats, chickens, piglets. The maximum non-lethal dose of CK-1 was 19 g/kg for white mice. The agent showed a low toxicity.