Synthesis and Characterization of Aluminium and Rare-Earth Ion Doped Strontium Ferrite Nanoparticles

Magnetic materials with high coercive fields, often called permanent magnets, have a wide industrial application ranging from loudspeakers to motors, and sensors. In particular, Strontium hexaferrite SrFe12O19 and Barium hexaferrite BaFe12O19 have received considerable attention trying to improve their magnetic properties because of their low price per unit of stored energy, which allows large scale production. Other factors such as high Curie temperature, excellent chemical stability, and light weight are associated with them. Many studies have focused on replacing Strontium (Sr) or Iron (Fe) atoms with magnetic and non-magnetic atoms to improve magnetic properties of these ferrites. The studies on Rare-Earth (RE) substituted SrFe12O19 are abound. However studies on non-magnetic ion substitution on SrFe12O19 are limited. Herein we present a study on the synthesis and characterization of Aluminium (Al) and RE doped SrFe12O19

Phase stability and electronic structures of perovskite and organic optoelectronic materials via first-principle calculations

Mixed ionic and electronic conductor oxides, in particular La1-xSrxCoyFe1-yO3-d (LSCF), have been widely used as the cathode materials in solid oxide fuel cells for high-temperature energy applications. The focus of this thesis is primarily on constructing the instability phase diagram of Sr segregations on LSCF surfaces at the experimentally relevant temperatures and oxygen partial pressures using the first-principles density functional theory (DFT). A generic first-principles free-energy functional is developed to obtain the nonstoichiometric oxygen vacancy concentrations for the bulk and surface phases. These results agree well with the corresponding thermo-gravimetry measurements, and furthermore suggest that the oxygen vacancies are energetically stabilized at surfaces for all temperatures and oxygen partial pressures, while such surface stabilization effects become stronger at higher temperatures and lower oxygen partial pressures. Based on these nonstoichiometric oxygen vacancy predictions, we construct the free-energy phase diagrams of the Sr-segregation reaction as a function of temperature, oxygen partial pressure, and CO2 partial pressure for both the bulk and surface LSCF phases. Our results suggest that Sr segregations strongly accumulate towards the LSCF surface phase where the oxygen vacancy nonstoichiometries are abundant. Our results also indicate that the Sr segregation reactions are significantly enhanced at high temperatures, low oxygen partial pressures, and high CO2 partial pressures. The computed reaction temperature ranges are consistent with the total reflection X-ray fluorescence (TXRF) measurements

Worldwide genetic variation of the IGHV and TRBV immune receptor gene families in humans.

The immunoglobulin heavy variable (IGHV) and T cell beta variable (TRBV) loci are among the most complex and variable regions in the human genome. Generated through a process of gene duplication/deletion and diversification, these loci can vary extensively between individuals in copy number and contain genes that are highly similar, making their analysis technically challenging. Here, we present a comprehensive study of the functional gene segments in the IGHV and TRBV loci, quantifying their copy number and single-nucleotide variation in a globally diverse sample of 109 (IGHV) and 286 (TRBV) humans from over a 100 populations. We find that the IGHV and TRBV gene families exhibit starkly different patterns of variation. In addition to providing insight into the different evolutionary paths of the IGHV and TRBV loci, our results are also important to the adaptive immune repertoire sequencing community, where the lack of frequencies of common alleles and copy number variants is hampering existing analytical pipelines

A Note on Entrepreneurial Risk, Capital Market Imperfections, and Heterogeneity

Empirical evidence shows that entrepreneurs hold a large fraction of wealth, have higher saving rates than workers, and face substantial uninsurable entrepreneurial and investment risks. This paper constructs a heterogeneous-agent general equilibrium model with uninsurable entrepreneurial risk and capital market imperfections to explore the implications of uninsurable entrepreneurial risk for wealth distribution and aggregate activity in an incomplete market economy. It is shown that entrepreurial risk can substantially affect both the wealth distribution and the macroeconomy.Wealth Distribution, Idiosyncratic Entrepreneurial Risk, Incomplete Capital Markets