Prediction of mineral dust properties at mine sites

Predicting the properties of dust generated at mine sites is important for understanding the impact of dust dispersal to the surrounding environment. This chapter presents a new approach to predicting the mineralogical properties of the PM2.5 and PM10 dust fractions. A purpose-built dust resuspension machine was fitted with a size selective sampler to collect dust fractions. Dust particles were collected onto a polycarbonate filter, which was analyzed using a scanning electron microscope (SEM). Backscattered electron (BSE) maps of the polycarbonate surface were imaged and processed to determine dust properties. For a given population of particles, the BSE brightness distribution of the 2-5 and 5-10 µm size fractions were quantified. The mineralogical composition of the dust size fractions were inferred by the BSE brightness as biogenic particles and sulfates (30-50), silicates (60-100), iron silicates and oxides (110-190), and sulfides (>200). The method was validated by comparing laboratory-generated dust fractions with those collected from dust monitoring stations at a tailings repository site. Similar dust composition and size fractions were observed for both laboratory and field samples. Consequently, the purpose-built dust resuspension device and associated laboratory procedures allow the prediction of mineralogical properties of dust at mine sites

Exercise does not affect stiffness and mineralisation of third metacarpal condylar subarticular calcified tissues in 2 year old thoroughbred racehorses

Impact exercise has a profound effect in increasing volumetric density of epiphyseal bone, as clearly shown in 2 year old thoroughbred racehorses from which we derived the tissue studied in the present investigation. Here, we asked the question whether the fabric-level properties of the mineralised tissues immediately below hyaline articular cartilage which transmit the extra loads are themselves altered in consequence. We therefore studied the nanoindentation elastic modulus and its relationship to the concentration of mineral determined by quantitative backscattered electron imaging in the heavily loaded palmar medial and lateral condyles of the distal third metacarpal bone (Mc3) of 4 untrained and 4 trained 2-year old Thoroughbred racehorses. We found no difference between trained and untrained horses in either subchondral bone or calcified cartilage in the mean stiffness or mineral content or their correlation. Thus neither articular calcified cartilage nor the immediately adjacent subchondral bone were affected by exercise, even though they transmitted the higher load associated with athletic training through to the deeper bone, which itself responded floridly to exercise. Under the circumstances of this experiment and at least in the very small regions studied, therefore, the structure of these two tissues was apparently optimised to function

Scanning Electron Microscopy of Bone.

This is a post-peer-review, pre-copyedit version of an article published in Methods in Molecular Biolog. The final authenticated version is available online at: https://doi.org/10.1007/978-1-61779-415-5_24This chapter describes methods for preparing samples of bone and bone cells for scanning electron microscopy (SEM). Backscattered electron (BSE) imaging is by far the most useful in the bone field, followed by secondary electrons (SE) and the energy dispersive X-ray (EDX) analytical modes. Samples may have 3D detail in a 3D surface, or be topography-free, polished or micromilled, resin-embedded block surfaces, or resin casts of space compartments surrounded by bone matrix. Methods for cells include fixation, drying, looking at undersides of bone cells, and metallic conductive coating. Maceration with alkaline bacterial pronase, hypochlorite, hydrogen peroxide, and sodium or potassium hydroxide to remove cells and unmineralized matrix is described in detail. Attention is given especially to methods for 3D BSE SEM imaging of bone samples. Recommendations are made for the types of resin embedding for BSE SEM imaging. Correlated confocal and SEM imaging of PMMA embedded bone requires the use of glycerol to coverslip. Cathodoluminescence (CL) mode SEM imaging is an alternative for visualizing fluorescent mineralizing front labels such as calcein and tetracyclines. Making spatial casts from PMMA or other resin-embedded samples is an important use of this material. Correlation with other imaging means, including microradiography and microtomography is important. Shipping wet bone samples between labs is best done in glycerol. Control of the vacuum pressure in the SEM sample chamber (now generally available) can be used to eliminate "charging" problems which were common, for example, with large, complex, cancellous bone samples.Horserace Betting Levy Boar

A mouse model for spondyloepiphyseal dysplasia congenita with secondary osteoarthritis due to a Col2a1 mutation

Progeny of mice treated with the mutagen N-ethyl-N-nitrosourea (ENU) revealed a mouse, designated Longpockets (Lpk), with short humeri, abnormal vertebrae, and disorganized growth plates, features consistent with spondyloepiphyseal dysplasia congenita (SEDC). The Lpk phenotype was inherited as an autosomal dominant trait. Lpk/+ mice were viable and fertile and Lpk/Lpk mice died perinatally. Lpk was mapped to chromosome 15 and mutational analysis of likely candidates from the interval revealed a Col2a1 missense Ser1386Pro mutation. Transient transfection of wild-type and Ser1386Pro mutant Col2a1 c-Myc constructs in COS-7 cells and CH8 chondrocytes demonstrated abnormal processing and endoplasmic reticulum retention of the mutant protein. Histology revealed growth plate disorganization in 14-day-old Lpk/+ mice and embryonic cartilage from Lpk/+ and Lpk/Lpk mice had reduced safranin-O and type-II collagen staining in the extracellular matrix. The wild-type and Lpk/+ embryos had vertical columns of proliferating chondrocytes, whereas those in Lpk/Lpk mice were perpendicular to the direction of bone growth. Electron microscopy of cartilage from 18.5 dpc wild-type, Lpk/+, and Lpk/Lpk embryos revealed fewer and less elaborate collagen fibrils in the mutants, with enlarged vacuoles in the endoplasmic reticulum that contained amorphous inclusions. Micro-computed tomography (CT) scans of 12-week-old Lpk/+ mice revealed them to have decreased bone mineral density, and total bone volume, with erosions and osteophytes at the joints. Thus, an ENU mouse model with a Ser1386Pro mutation of the Col2a1 C-propeptide domain that results in abnormal collagen processing and phenotypic features consistent with SEDC and secondary osteoarthritis has been established