Movements are associated with a beta (15-30 Hz) power decrease during movement preparation and a rebound after its termination. Motor learning and practice are characterized by an increase of the ...rebound. However, the introduction of a sensorimotor perturbation negatively affects such measure. In this preliminary study, we investigated whether two learning processes affect beta electroencephalographic activity: (a) learning to perform a center-out reaching task by moving a passive robotic arm, and (b) learning to reach the same targets in the presence of a velocity-dependent force field. Seven subjects were exposed to the (a), then to the (b) condition. Results revealed that beta power rebound and its latency increased with practice with the passive manipulandum. When the force field was applied, beta power rebounded and its latency immediately dropped, but they started to increase again with the prolonged exposure to the predictable perturbations. These results suggest that increased rebound in beta power reflects cortical activity elicited by the correct prediction of movement outcomes.
Sinorhizobium meliloti is a soil bacterium that fixes atmospheric nitrogen in plant roots. The high genetic diversity of its natural populations has been the subject of extensive analysis. Recent ...genomic studies of several isolates revealed a high content of variable genes, suggesting a correspondingly large phenotypic differentiation among strains of S. meliloti. Here, using the Phenotype MicroArray (PM) system, hundreds of different growth conditions were tested in order to compare the metabolic capabilities of the laboratory reference strain Rm1021 with those of four natural S. meliloti isolates previously analyzed by comparative genomic hybridization (CGH). The results of PM analysis showed that most phenotypic differences involved carbon source utilization and tolerance to osmolytes and pH, while fewer differences were scored for nitrogen, phosphorus, and sulfur source utilization. Only the variability of the tested strain in tolerance to sodium nitrite and ammonium sulfate of pH 8 was hypothesized to be associated with the genetic polymorphisms detected by CGH analysis. Colony and cell morphologies and the ability to nodulate Medicago truncatula plants were also compared, revealing further phenotypic diversity. Overall, our results suggest that the study of functional (phenotypic) variability of S. meliloti populations is an important and complementary step in the investigation of genetic polymorphism of rhizobia and may help to elucidate rhizobial evolutionary dynamics, including adaptation to diverse environments.
A procedure for the optimization of a 3C–SiC buffer layer for the deposition of 3C–SiC/(001) Si is described. After a standard carbonization at 1125°C, SiH4 and C3H8 were added to the gas phase while ...the temperature was raised from 1125°C to the growth temperature of 1380°C with a controlled temperature ramp to grow a thin SiC layer. The quality and the crystallinity of the buffer layer and the presence of voids at the SiC/Si interface are related to the gas flow and to the heating ramp rate. In order to improve the buffer quality the SiH4 and C3H8 flows were changed during the heating ramp. On the optimized buffer no voids were detected and a high-quality 1.5μm 3C–SiC was grown to demonstrate the effectiveness of the described buffer.
•A procedure for the optimization of a 3C–SiC buffer layer for the deposition of 3C–SiC/(001) Si is presented.•Buffer layer quality and voids at interface depends on the gas flow and heating ramp rate. Lower ramp heating rate yield the best results.•On the optimized buffer very few density of voids were detected.•High-quality 1.5μm 3C–SiC was grown to demonstrate the effectiveness of the described buffer.
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