Impedance Study of Temperature-Stable Relaxor Dielectrics in the System of BCT-BMT Ceramics.

Preparation of a lead-free system (Ba0.8Ca0.2)TiO3-xBi(Mg0.5Ti0.5)O3 (BCT-BMT) with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was carried out using a solid-state reaction technique. X-ray (XRD) diffraction analysis confirmed a tetragonal structure for x = 0, which shifted to cubic (pseudocubic) at x ≥ 0.1. From Rietveld refinement, a single phase with a tetragonal symmetry model (P4mm) was observed for x = 0, and however, for sample x = 0.1 and sample x = 0.5, the data are modeled to cubic (Pm3m). Composition x = 0 showed a prominent Curie peak, typical of ordinary ferroelectrics with a Curie temperature (Tc) ∼130 °C, modified to a typical relaxor dielectric at x ≥ 0.1. However, samples at x = 0.2-0.5 displayed a single semicircle attributed to the bulk response of the material, whereas a slightly depressed second arc appeared for x = 0.5 at 600 °C, indicating a slight contribution to the electrical properties, ascribed to the grain boundary of the material. Finally, the dc resistivity increased with the increase of the BMT content and the solid solution increased the activation energy from 0.58 eV at x = 0 to 0.99 eV for x = 0.5. Adding the BMT content eliminated the ferroelectric behavior at compositions x ≥ 0.1 and led to a linear dielectric response and electrostrictive behavior with a maximum strain of 0.12% for x = 0.2.

A South African database of samples analysed for the presence of asbestos

Background: Asbestos mining and other activities have left a legacy of environmental contamination. Asbestos was used in a large number of manufactured products but little is documented about the nature and location of these products. Compliance with asbestos regulations depends on accurate identification of the presence of asbestos. The National Institute for Occupational Health (NIOH) has been identifying asbestos for regulatory purposes since 2003. Objective: To analyse a database of samples submitted for asbestos analysis to the NIOH. Methods: Asbestos was identified using scanning electron microscopy and energy dispersive spectroscopy. The data were analysed using STATISTICA version 11. Results: From 2003 to 2012; 1514 samples were analysed. Asbestos was identified in 59.9 of the bulk samples and crocidolite was present in 45.4 of these. Information about samples containing asbestos; including their origin and associated activities; are described. Conclusions: Although asbestos is no longer mined or used in South Africa; workers remain at risk of exposure due to asbestos-containing materials which persist in the environment. Knowledge of these materials gained from routinely collected data may assist in the safe removal of asbestos and prevent further adverse health =effects

Characterization of dentine structure in three dimensions using FIB-SEM.

All biological tissues are three dimensional and contain structures that span a range of length scales from nanometres through to hundreds of millimetres. These are not ideally suited to current three-dimensional characterization techniques such as X-ray or transmission electron tomography. Such detailed morphological analysis is critical to understanding the structural features relevant to tissue function and designing therapeutic strategies intended to address structural deficiencies encountered in pathological states. We show that use of focused ion beam milling combined with scanning electron microscopy can provide three-dimensional information at nanometre resolution from biologically relevant volumes of material, in this case dentine.

Nanoparticles for dentine tubule infiltration: an in vitro study.

Nanosized particles of hydroxyapatite were produced by a hydrothermal synthesis technique. Reaction time and starting pH were varied in order to produce a range of particle dimensions and morphologies. The particles were suspended in alcohol and used for in-vitro trials of dentinal tubule infiltration in etched sections of clinically extracted human molars. Particles were of rod-like morphology, and decreased in aspect ratio as the starting pH was raised. Particles prepared at pH 12 had a mean length of approximately 70 nm and diameter of approximately 30 nm. These showed the most promising infiltration results, with up to 90% of the tubules being fully or partially occluded. Comparisons were made with commercially-available 40 nm spherical silica particles. Information on the depth of infiltration was obtained from sections of dentine prepared using focussed ion beam milling (FIB-SEM).

The fluorescent detection of Paradiplozoon sp. (Monogenea: Diplozoidae) attachment clamps' sclerites and integumental proteins.

In the genus Paradiplozoon, few hard structures are present therefore most of the taxonomic studies have focused on the unique ultrastructure of the sclerites. Alcohol-fixed specimens were transferred to BSA-saline for 5 min. before staining indefinitely with 5 microl WGA-TRX, 5 microl SYTO 9 and 5 microl of Calcofluor White M2R. Rhodamine, Fluorescein and DAPI bandpass filters on the microscope enabled selective light wavelength illumination of the three flourochromes by a mercury light source. This method provided an easy and rapid methodology to show the internal sclerites of attachment clamps. It is suitable for alcohol preserved specimens and may have additional applications in other helminth organisms.