Observation of nanoscale magnetic fields using twisted electron beams

Electron waves give an unprecedented enhancement to the field of microscopy by providing higher resolving power compared to their optical counterpart. Further information about a specimen, such as electric and magnetic features, can be revealed in electron microscopy because electrons possess both a magnetic moment and charge. In-plane magnetic structures in materials can be studied experimentally using the effect of the Lorentz force. On the other hand, full mapping of the magnetic field has hitherto remained challenging. Here we measure a nanoscale out-of-plane magnetic field by interfering a highly twisted electron vortex beam with a reference wave. We implement a recently developed holographic technique to manipulate the electron wavefunction, which gives free electrons an additional unbounded quantized magnetic moment along their propagation direction. Our finding demonstrates that full reconstruction of all three components of nanoscale magnetic fields is possible without tilting the specimen

Estimating Terrestrial Primary Productivity by Combining Remote Sensing and Ecosystem Simulation

Beginning in 1972 with the launch of Landsat 1, estimation of terrestrial plant production has been one of the most important applications attempted of satellite remote sensing. Initial interest focused on the prediction of regional crop yields, such as wheat (Erickson, 1984). However, changing goals, hardware capabilities, and theory have produced a steady evolution in the approaches taken to calculate net primary production (NPP) of large areas. Interest has also expanded to calculating primary production of natural vegetation. The much wider array of topography, climate, canopy geometry, and life-cycle dynamics exhibited by natural vegetation make computation of primary production much more challenging than the rather controlled, organized field conditions of a crop