21 research outputs found
Computational study of crystallography, defects, ion migra-2 tion and dopants in almandine garnet
Almandine garnet has received considerable amounts of interest due to its application in manufacturing and engineering processes. Defect processes, Fe-ion diffusion pathways, and promising dopants on the Al, Fe, and Si sites are examined using classical pair potential simulations in almandine garnet. The cation antisite (Al–Si) defect cluster is the most favourable defect, highlighting the cation disorder in this material. A three-dimensional long-range Fe-ion diffusion pathway with an activation energy of 0.44 eV suggests that the ionic conductivity in this material is high. The most favourable isovalent dopants on the Fe, Al, and Si sites were found to be the Mn, Ga, and Ge, respectively. Subvalent doping of Ga on the Si site is a favourable process to increase the Fe content in this material
Proteomics of Buccal Cavity Mucus in Female Tilapia Fish (Oreochromis spp.): A Comparison between Parental and Non-Parental Fish
Mouthbrooding is an elaborate form of parental care displayed by many teleost
species. While the direct benefits of mouthbrooding such as protection and
transportation of offsprings are known, it is unclear if mouthbrooding offers
additional benefits to embryos during incubation. In addition, mouthbrooding
could incur negative costs on parental fish, due to limited feeding
opportunities. Parental tilapia fish (Oreochromis spp.) display
an elaborated form of parental care by incubating newly hatched embryos in oral
buccal cavity until the complete adsorption of yolk sac. In order to understand
the functional aspects of mouthbrooding, we undertake a proteomics approach to
compare oral mucus sampled from mouthbrooders and non-mouthbrooders,
respectively. Majority of the identified proteins have also been previously
identified in other biological fluids or mucus-rich organs in different
organisms. We also showed the upregulation of 22 proteins and down regulation of
3 proteins in mucus collected from mouthbrooders. Anterior gradient protein,
hemoglobin beta-A chain and alpha-2 globin levels were lower in mouthbrooder
samples. Mouthbrooder oral mucus collectively showed increase levels of proteins
related to cytoskeletal properties, glycolytic pathway and mediation of
oxidative stress. Overall the findings suggest cellular stress response,
probably to support production of mucus during mouthbrooding phase
The origin and composition of carbonatite-derived carbonate-bearing fluorapatite deposits
Carbonate-bearing fluorapatite rocks occur at over 30 globally distributed carbonatite complexes and represent a substantial potential supply of phosphorus for the fertiliser industry. However, the process(es) involved in forming carbonate-bearing fluorapatite at some carbonatites remain equivocal, with both hydrothermal and weathering mechanisms inferred. In this contribution, we compare the paragenesis and trace element contents of carbonate-bearing fluorapatite rocks from the Kovdor, Sokli, Bukusu, Catalão I and Glenover carbonatites in order to further understand their origin, as well as to comment upon the concentration of elements that may be deleterious to fertiliser production. The paragenesis of apatite from each deposit is broadly equivalent, comprising residual magmatic grains overgrown by several different stages of carbonate-bearing fluorapatite. The first forms epitactic overgrowths on residual magmatic grains, followed by the formation of massive apatite which, in turn, is cross-cut by late euhedral and colloform apatite generations. Compositionally, the paragenetic sequence corresponds to a substantial decrease in the concentration of rare earth elements (REE), Sr, Na and Th, with an increase in U and Cd. The carbonate-bearing fluorapatite exhibits a negative Ce anomaly, attributed to oxic conditions in a surficial environment and, in combination with the textural and compositional commonality, supports a weathering origin for these rocks. Carbonate-bearing fluorapatite has Th contents which are several orders of magnitude lower than magmatic apatite grains, potentially making such apatite a more environmentally attractive feedstock for the fertiliser industry. Uranium and cadmium contents are higher in carbonate-bearing fluorapatite than magmatic carbonatite apatite, but are much lower than most marine phosphorites