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Title: Transmission-mode imaging in the environmental scanning electron microscope (ESEM
Author: Staniewicz, Lech Thomas Leif
ISNI:       0000 0004 2713 7234
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2012
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Electron microscopy was first conducted in the 1930s with the advent of theTEM and later the STEM. In 1969, the first commercial SEM was released,with the possibility of retrofitting it to behave like a STEM following soonafterwards. In 1979, Danilatos and Robinson advanced electron microscopyby creating a new type of SEM which allowed a controlled quantity of gasinto the sample chamber, termed ESEM. The most recent evolution in thisline was the combination of ESEM and STEM in 2005, a procedure termedWet STEM.The focus of this work is on investigating applications of this new technique,along with the contrast mechanisms involved in forming an image. Tothat end, a wide variety of samples will be imaged. Clay and paint suspensions(colloids) are used to test Wet STEM’s capacity to image submergedobjects, as well as thin objects which are stacked together. Diblock copolymerfilms are used to test Wet STEM’s ability to distinguish chemically similarmaterials without staining, the physical effects of heavy metal staining andto demonstrate the necessity of gas for the purpose of charge neutralisation. Single cell biological samples are also investigated. Internal contrast inmammalian cells is visible without recourse to staining, but chemical fixationis required despite maintaining a high relative humidity. Bacteria are moreresilient and as such are easier to image than animal cells, requiring no priortreatment. When exposed to low relative humidity, bacteria are found tocollapse. The collapse pattern is observed to differ between wild-type andcytoskeletal-deficient bacteria of the same species and strain, so it is likelythat dehydration-induced collapse offers information about the position andshape of the bacterial cytoskeleton.
Supervisor: Donald, Athene ; Stokes, Debbie Sponsor: ; CASE studentship from FEI Company
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Electron microscopy ; ESEM ; STEM ; Polymers ; Bacteria ; Clay ; Colloids