Improved apparatus for trapped radical and other studies down to 1.5 K.
This note describes a Dewar system and associated apparatus for trapped free radical and other studies at temperatures down to 1.5 K. Cylindrical and rectangular microwave cavities can be used.
AN OPTICAL CELL FOR USE WITH LIQUID HELIUM
A low temperature cell is described that permits spectral absorption and emission measurements, as well as high energy irradiation of materials held at liquid helium temperatures. The liquid helium capacity of one liter is sufficient for up to 24 hours of continuous operation. Any substance whether it be solid, liquid, or gas at room temperatures can be studied. The all‐metal cell is entirely portable and can be employed with a number of instruments without modification. A sylphon bellows arrangement permits vertical displacement within the cell of the samples under study.
Remote estimation of nitrogen and chlorophyll contents in maize at leaf and canopy levels
a b s t r a c t Leaf and canopy nitrogen (N) status relates strongly to leaf and canopy chlorophyll (Chl) content. Remote sensing is a tool that has the potential to assess N content at leaf, plant, field, regional and global scales. In this study, remote sensing techniques were applied to estimate N and Chl contents of irrigated maize (Zea mays L.) fertilized at five N rates. Leaf N and Chl contents were determined using the red-edge chlorophyll index with R2 of 0.74 and 0.94, respectively. Results showed that at the canopy level, Chl and N contents can be accurately retrieved using green and red-edge Chl indices using near infrared (780-800 nm) and either green (540-560 nm) or red-edge (730-750 nm) spectral bands. Spectral bands that were found optimal for Chl and N estimations coincide well with the red-edge band of the MSI sensor onboard the near future Sentinel-2 satellite. The coefficient of determination for the relationships between the red-edge chlorophyll index, simulated in Sentinel-2 bands, and Chl and N content was 0.90 and 0.87, respectively.