RESUMO
Using first-principles transport calculations, we predict that the anisotropic magnetoresistance (AMR) of single-crystal Co_{x}Fe_{1-x} alloys is strongly dependent on the current orientation and alloy concentration. An intrinsic mechanism for AMR is found to arise from the band crossing due to magnetization-dependent symmetry protection. These special k points can be shifted towards or away from the Fermi energy by varying the alloy composition and hence the exchange splitting, thus allowing AMR tunability. The prediction is confirmed by delicate transport measurements, which further reveal a reciprocal relationship of the longitudinal and transverse resistivities along different crystal axes.
RESUMO
Scanning electron microscope and energy-dispersive X-ray analysis were used to study the tissular distributions of elements Na, Mg, Cl, K, Ca, Mn, and Fe in leaves of cucumber seedlings in the absence or presence of La3+. The results showed that the atomic percentages of Na, Mg, Cl, K, and Ca were basically reduced and those of Mn and Fe were increased in the presence of La3+; in addition, at 0.02 mM La3+, the reduced or increased degrees were higher than those at 2.0 mM La3+. The effects of La3+ on ion absorption were similar to those of Ca2+, suggesting that the rare earth element lanthanum affects the plant physiological mechanism by regulating the Ca2+ level in plant cell.
Assuntos
Cucumis sativus/metabolismo , Lantânio/farmacologia , Oligoelementos/metabolismo , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/crescimento & desenvolvimento , Microscopia Eletrônica de Varredura/métodos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Sementes/efeitos dos fármacos , Oligoelementos/análise , Raios XRESUMO
The abscisic acid (ABA) content of the root tips of four crops grown in lanthanide chloride solution and their root lengths had been determined. At lanthanide concentrations of 5 and 10 ppm, these crops all grew well and the ABA decreased. At higher lanthanide concentrations (100-500 ppm), the ABA is increased again. At these concentrations of lanthanum chloride, the photosystems I and II (PSI and PSII) and whole electron chain transport activities were inhibited. PSII was more sensitive than PSI, and it is concluded that La3+ acts on the diphenylcarbazide (DPC) action place of PSII oxidizing site.