deletions | additions       diff --git a/section_Wet_SEM_From_the__.tex b/section_Wet_SEM_From_the__.tex  index 1459ab9..b296c11 100644  --- a/section_Wet_SEM_From_the__.tex  +++ b/section_Wet_SEM_From_the__.tex 
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\end{equation}  where the $K=0.064$ and $\gamma = 1.68$ with $E_0$ being the energy of the primary beam in $KeV$. And $\rho$ is the density of the gas in $g/cm^3$, approximated by the ideal gas relationship. From Eq. (17), the electron range for $1atm$ nitrogen is found to be $20 \sim 300 \mu m$ for energy $E_0 = 5 \sim 30 KeV$. The electron range is less than the working distance; thus, only a very small fraction of the primary electrons will reach and sample. Both the SE (with range $\approx$ several nanometers) and BSE (with range from nanometer to micrometer) cannot reach the detector with working distance $d = 5\sim 10 mm$ away. Without the possibility of operating ESEM in $1atm$, the sample protection should be introduced to avoid evaporation and drying effects.  The protected sample in a fully hydrated system is the typical sample for Wet SEM\cite{Thiberge_2004}. The protection of the sample can totally rule out the particle exchange between the specimen and the sample chamber. The high pressure of sample chamber becomes redundant so the sample chamber is pumped at low pressure similar to the conventional SEM. Wet SEM relies on a thin, membranous partition that protects the fully hydrated smaple from the vacuum while being transparent to the beam electrons. electrons, shown in Fig.5 a.  Such thin membranes must be nonconducting to have minimun interaction with electrons and strong enough to withstand the pressure difference across it. The polymer membranes turn out to be good candidates and polyimide membranes with the thickness of $145nm$ were found to be the best. The thickness of the protection layer prevents the SE produced inside the membrane from escaping out of the sample. The SE signals are lost. However, the BSE signals are well preserved due to its high energy in general. The Wet SEM takes advantage of the properties of the BSE to construct many images of high resolution and component dependence. The introduction of the polyimide membrane enables different ways of insertion of the specimen close to the membrane for better BSE resolution. Biological specimens such as bacteria, algae and Fungi cells can grow directly on the membranes before insertion into the sample. For some inorganic materials, the membranes can be brought into contact either manually or mechanically. It is desired that the specimens being adhered to the lower surface of the membrane to have the best image and resolution. The main problem of the polyimide protection membranes is that the membranes will swell outwards like a balloon because of the pressure differences. The swelling might distort the specimen, making some parts of it deeper and some shallower. The image will appear brighter in the center and darker at the edge. A tiny leakage opening with radius $\approx $ will be designed on the membrane to allow limited exchange of particles and reduce the strain in the membrane, as shown in Fig.5 a. b.  The thickness of the membranes can also be reduced from $145 nm$ to $50 nm$. The tiny hole and the thinner membranes further enable imaging with SE signals. With this set up, it was claimed that the spatial resolution could achieve the best resolution of conventional SEM down to $10 nm$ with heavy atomic stains and $100 nm$ in stainless samples. samples, shown in Fig.5 d.