Control mechanisms of microtubule overlap regions

Measurement of Pore Sizes in Fine‐textured Soils: A Review of Existing Techniques

“…The limited use of thin sectioning for the study of pores may have been for several reasons (a) there is the problem of distinguishing soil pores from mineral grains, although this has often been overcome by the addition of fluorescent dyes t o impregnating resins (Fitzpatrick, 1970), (b) the difficulties in translating two dimensional images into volumes (Brewer, 1964), (c) the restricted range of pore size that can be measured due t o the practical limit of resolution of the optical microscope (about lo3 nm): in clay soils the majority of pores are < lo3 nm, (d) the tedious nature of measuring pore size distributions; this time factor has now been overcome t o a large extent by automatic analysing instruments such as Quantimet-B equipment (Jongerius et al, 1972), although these are very costly and (e) the need to dry soils before impregnation when using resins of the polyester, epoxy and polystyrene type, causing sample shrinkage; polyethylene glycols e.g. Carbowax 6000 have been used to impregnate wet clay samples (Morgenstern and Tchalenko, 1967) but this treatment has been found to cause up t o 20 per cent volumetric shrinkage (Greene-Kelly, 197 1 ).…”