a b s t r a c tCalcium carbonate nanofibres are found in numerous terrestrial environments, often associated with needle fibre calcite. This study attempts to mimic the natural system and generate comparable crystalline structures. A comparison of natural and synthesized nanofibre structures, using HRTEM as well as electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI), has demonstrated that this type of nanocrystal can result from precipitation on organic templates, most likely cellulose nanofibres. This study emphasizes the fundamental role of organic templates in the precipitation of calcium carbonate in vadose environments, even at the nanoscale.

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Online NobleChem is a technology to mitigate stress corrosion cracking in reactor internals and recirculation pipes of boiling water reactors (BWRs). For a more efficient reduction of the electrochemical corrosion potential (ECP) under hydrogen water chemistry conditions, noble metals (e.g. Pt) are injected into the feed water during power operation. They are claimed to deposit as very fine metallic particles on all water wetted surfaces and to stay electrocatalytic over long periods. To study the deposition and (re)distribution behaviour of Pt, a sophisticated high temperature water loop has been constructed, in which specimens can be exposed to simulated BWR water and Pt can be deposited in situ. The specimens are analysed by laser ablationinductively coupled plasma-mass spectrometry and electron microscopy after the experiments. Results from two experiments with different Pt injection rates but similar total Pt amounts revealed a faster and more pronounced reduction of the ECP and slightly larger average Pt particle size using the higher Pt injection rate. A longer preoxidation of the specimens seems to increase the average Pt concentration on the specimen surface.7 Bright field (TEM) image of a, c non-preoxidised and b, d preoxidised specimens with Pt nanoparticles (pointed with arrows) from test 1 Ramar et al. Effect of Pt injection rate on corrosion potential and Pt distribution Corrosion Engineering, Science and Technology 2012 VOL 47 NO 7 495

We carried out a high-resolution ultrastructural analysis of the nucleolus in mouse P815 cells by combining specific DNA and RNA staining, anti-fibrillarin immunolabeling, contrast enhancement by energy filtering TEM and phosphorus mapping by ESI to visualize nucleic acids. We demonstrated that specifically contrasted DNA, fibrillarin and phosphorus overlap within the nucleolar dense fibrillar component. Moreover, we describe a ‘DNA cloud’ consisting of an inner core of DNA fibers (fibrillar center) and a periphery made of extremely thin fibrils overlapping the anti-fibrillarin immunolabeling (dense fibrillar component). This highly sensitive approach has allowed us to demonstrate, for the first time, the exact distribution of DNA within the decondensed interphase counterpart of the NOR, which includes both the fibrillar center and the dense fibrillar component.

The in situ distribution of phosphorus in perichromatin granules (PCGs), and in the surrounding nucleoplasm was investigated in rat liver cells by means of electron spectroscopic imaging of unstained preparations. A 2-3 nm fibril containing high concentration of phosphorus was found to be the main substructural feature of the PCGs revealed in the maps of phosphorus. This fibril is folded within the PCG with no apparent order. Fibrils of similar diameter and phosphorus content were also found in both the halo surrounding the PCG and dispersed in the nucleoplasm. Some of such fibrils are in continuity with those occurring within PCGs. Sometimes these fibrils are grouped forming a stalk connecting the PCG to chromatin. Some stalked PCGs are U-shaped or kidney-shaped, resembling Balbiani ring granules in the process of formation as observed in Chironomus salivary gland cell nuclei. The external fibrils are interpreted as perichromatin fibrils considered to be precursors of PCGs.