Sistematização de metadados de parcelas permanentes.

Resumo

High coercivity induced by mechanical milling in cobalt ferrite powders

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 treated by mechanical milling with different grinding balls. The cobalt ferrite nanoparticles were prepared using a simple hydrothermal method and annealed at 500oC. The non-milled sample presented coercivity of about 1.9 kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42. After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To investigate the influence of the microstructure on the magnetic behavior of these samples, we used X-ray powder diffraction (XPD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by the Williamson-Hall plot was used to estimate the average crystallite size and strain induced by mechanical milling in the samples

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE

Superscars in the LiNC=LiCN isomerization reaction

We demonstrate the existence of superscarring in the LiNC=LiCN isomerization reaction described by a realistic potential interaction in the range of readily attainable experimental energies. This phenomenon arises as the effect of two periodic orbits appearing "out of the blue"in a saddle--node bifurcation taking place in the dynamics of the system. Potential practical consequences of this superlocalization in the corresponding wave functions are also considered.Comment: 6 pages, 5 figures. to appear in EP

Universal quantum signature of mixed dynamics in antidot lattices

We investigate phase coherent ballistic transport through antidot lattices in the generic case where the classical phase space has both regular and chaotic components. It is shown that the conductivity fluctuations have a non-Gaussian distribution, and that their moments have a power-law dependence on a semiclassical parameter, with fractional exponents. These exponents are obtained from bifurcating periodic orbits in the semiclassical approximation. They are universal in situations where sufficiently long orbits contribute.Comment: 7 page

\u3cem\u3eBrachiaria Spp.\u3c/em\u3e (Syn. \u3cem\u3eUrochloa Spp.\u3c/em\u3e) CV. Mulato Ii (Convert HD364) Mass Production Under Continuous Grazing in the Water/Dry Transition Period

In the transition period between the rainy and dry seasons there is decreased water, temperature and luminosity, reducing forage production and quality. Because of this variability in forage mass production, it is essential to quantify forage mass for use in planning and decision making about pastures management. The objective was to evaluate Brachiaria spp. (Syn. Urochloa spp.) cv. Mulato II (Convert HD364) growth, biomass production managed under continuous grazing with steers fed with protein supplement feed in-trough and on-ground during the seasonal transition period. The experiment was carried out in the Beef Cattle Sector of Jatai Federal University (UFJ), Brazil, from March to June 2020, in a completely randomized design, using 18 male Nellore steers at 24 months of age, with two animals per paddock. Variance analysis was performed by SAS software using the GLM procedure and time repeated measures with significance set to P \u3c 0.05. There was no significant difference between way of supplementation. In the rainy/drought transition period, Convert-grass produced 7,622 kg DM/ha and 1,995 kg DM/ha of leaf mass. The pelleted protein supplement can be used both in-trough or with onground because the method of feeding did not change the forage offered but the canopy was undergrazed which could biased the responses to the supply method evaluated

Effects of contrasting irradiances on carbon balance, biomass partition, and leaf nutrient contents in brazilian cerrado woody species.

It was evaluated growth and photosynthetic peformance of two leguminosae woody species under contrasting irradiances environments, Anadenanthera falcata (Benth.) Speg. and Stryphnodendron adstringens (Mart.) Coville. Under total irradiance in open area both species presented greater biomass accumulation, height, stem diameter, total leaf area and higher photosynthetic capacity on area bases (Amaxa). Shaded individuals under canopy modified the biomass partition, presenting greater mean values of leaf area rate (LAR), and smaller values of the specific leaf mass (SLM), repiration in dark (Rd), and apparent photorespiration (Pr) , apparent carboxylation efficiency (eletron transport rate (J). High transitory concentrations of CO2 increased the photosynthetic capacity under total irradiance (83%) and under canopy (71%)