An improved scanning system for a high-voltage electron microscope.

BACKGROUND AND AIMS: Silica deposition is one of the important characteristics of plants in the family Poaceae. There have been many investigations into the distribution, deposition and physiological functions of silica in this family. Two hypotheses on silica deposition have been proposed based on these studies. First, that silica deposition occurs passively as a result of water uptake by plants, and second, that silica deposition is controlled positively by plants. To test these two apparently contradictory hypotheses, silica deposition in relation to the ageing of leaf tissues in Sasa veitchii was investigated. METHODS: Tissues were examined using a light microscope and a scanning electron microscope equipped with an energy dispersive X-ray microanalyser. KEY RESULTS: The deposition process differed depending on cell type. In mesophyll tissue, fusoid cells deposited large amounts of silica depending on leaf age after maturation, while chlorenchyma cells deposited little. In epidermal tissue, comprised of eight cell types, only silica cells deposited large amounts of silica during the leaf's developmental process and none after maturation. Bulliform cells, micro-hairs and prickle hairs deposited silica densely and continuously after leaf maturation. Cork cells, guard cells, long cells and subsidiary cells deposited silica at low levels. CONCLUSIONS: The significance of these observations is discussed in relation to the two hypotheses proposed for silica deposition in Poaceae. The results of the present study clearly indicate that both hypotheses are compatible with each other dependent on cell types.

Microscopy, Electron, Scanning↗

PubMed2003

Studies on a poly(styrene-divinylbenzene)-encapsulated sub-micrometer sized organic-inorganic hybrid silica packing, its synthesis, some of its characteristics and applications.

The hydrolyzed product of a mixture of tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTEOS) was used to produce organic-inorganic hybrid silica by sol-gel processing. The product was a kind of composite with vinyl groups incorporated into the structure of the final particles through C-Si bonds. These hybrid silica particles were spherical and the average diameter was about 350 nm as measured by scanning electron microscopy (SEM). The particles were non-porous as proved by BET method. The hybrid silica particles were subsequently encapsulated with a layer of PS-DVB, a polymeric mixture of styrene and divinylbenzene, with the vinyl groups on the particle surface as anchors of the polymer chains. The encapsulated packing was used as stationary phases in CEC, and the chromatographic behaviors were studied. Experimental results showed that, as expected, the smaller diameter stationary phase resulted in higher column efficiencies. In comparison with the columns packed with 5 microm diameter encapsulated-silica stationary phases of the same kind and other sub-micron stationary phases reported, it can be concluded that the EOF velocity is independent of the particle diameter when using 350 nm phase, but determined by the surface nature of the stationary phase.

Microscopy, Electron, Scanning↗

PubMed2003

Structure and physicochemical properties of starches from kidney bean seeds at immature, premature and mature stages of development.

Starches from kidney bean (Phaseolus vulgaris L. cv. Toramame) seeds at the immature, premature, mature stages of development were examined. The starch content increased from 94, 219 to 265 mg per seed. Starches showed the C(a)-crystalline type composed of small (<5 micrometer) and large (10-35 micrometer) granules, with the large granules largely increasing with maturity. The amylose content increased from 21, 26 to 27%, and rapid viscograms and DSC thermograms suggested that the mature-stage starch was gelatinized with ease. The amylose increased in size from DPn 820, 1000 to 1080 and a number of chains per molecule (NC) from 3.3, 4.2 to 4.5. The branched amylose was a minor component (11-18% by mole) with NC 20-22. The amylopectin was similar in CL (23), beta-amylolysis limit (59%), and chain-length distribution, but reduced in size (DPn 17,100-5270) and increased in content of phosphorus (114-174 ppm) with an increase in the amount of phosphorus linked to C-6 of the glucose residue (8-66%).

Microscopy, Electron, Scanning↗