deletions | additions       diff --git a/ESEM_provides_the_suitable_environment__.tex b/ESEM_provides_the_suitable_environment__.tex  index 72c7926..5e976ab 100644  --- a/ESEM_provides_the_suitable_environment__.tex  +++ b/ESEM_provides_the_suitable_environment__.tex 
...
The samples imaged by Collins et. al. 1993\cite{Collins_1993} were the eukaryotic algae \textit{E. gracilis}, \textit{Spirogyra} and \textit{Saprolegnia} cells in either fully hydrated system or cryogenics states. The selected images are shown in Fig.2. In preparation of the sample, the cells were washed by deionized water and kept in a cacodylate buffer solution of pH 7.2. The samples were then fixed in formaldehyde for several minutes and ready to be imaged. The samples were imaged with or without metal coating under different primary beam energy ($20$ or $30 KeV$) by ESD or BSE detector signals. Moreover, the thickness of the sample was less than $10\mu m$ for imaging purposes. The environment for hydrated state was maintained $3 \sim 5 \space Torr$ water vapor and $4 ^{\circ}C$.   \textbf{ESD \raggedright\textbf{ESD  Images} The ESD images reflected the surface topology and the protein detectors and functional organs on the membranes of the cells can be clearly seen and identified. The resolution of the ESD images strongly depends upon the environment but are generally below $1 \mu m$ for $20 KeV$ primary beam. The dark and bright contrast represents the relative depth of different cells as discussed in SE sections. The limitation for ESD images is that the internal structures are obscure. The nucleus and other organelles cannot be seen by ESD images.