Produção de mudas de cupuaçu.

bitstream/item/78803/1/FOL-4806-0001.pd

Metal-Insulator Transition in a Disordered Two-Dimensional Electron Gas in GaAs-AlGaAs at zero Magnetic Field

A metal-insulator transition in two-dimensional electron gases at B=0 is found in Ga(Al)As heterostructures, where a high density of self-assembled InAs quantum dots is incorporated just 3 nm below the heterointerface. The transition occurs at resistances around h/e^2 and critical carrier densities of 1.2 10^11cm^-2. Effects of electron-electron interactions are expected to be rather weak in our samples, while disorder plays a crucial role.Comment: 4 pages, 3 figures, 21 reference

Third-order nonlinearities and other properties of molybdenum lead-pyrophosphate glass

Glasses in the binary system (100-x)Pb2P2O7-xMoO3, with x = 10 – 80 mol %, were synthesized by conventional melt-quenching technique. Thermal analysis, linear optical absorption, refractive index measurements, Raman scattering and nonlinear (NL) optical experiments were performed to characterize the samples. The dependence of MoO3 content on thermal, structural and optical properties was investigated. Molybdenum oxide increases both the glass transitions temperature and thermal stability against devitrification up to 50 mol % due to formations of P-O-Mo linkages and the glass network connectivity increases. The nonlinear optical properties were studied at 1064 nm and 532 nm with pulses of ≈17 ps. The NL refractive index measured was +10-19 m2/W at both wavelengths for samples with different relative concentrations of the constituent compounds. At 1064 nm we determined that the two-photon absorption coefficient, , is smaller than the minimum that we can measure ( <0.01 cm/GW) while at 532 nm we measured  0.25 cm/GW. The nonlinear response of the samples is attributed to contributions from the lone electron pairs of Pb2+, MoO3 clusters, and to Mo5+ and Mo4+ ions

Detection of two endornavirus in common bean genotypes in Brazil.

Endornaviruses (Endornaviridae) are persistent viruses that infect important crops such as pepper, rice, broad bean, and beans. However, these viruses are poorly studied and have not yet been reported in Brazil. In this study, we investigated the occurrence of two endornaviruses, Phaseolus vulgaris endornavirus-1 (PvEV-1) and Phaseolus vulgaris endornavirus-2 (PvEV-2) in bean genotypes

Detection and partial molecular characterization of isolates of Grapevine leafroll-associated virus 4 and Grapevine rupestris vein feathering virus.

Resumo apresentado de número 371-2