Impurity removal from Si by Si-Ca-Mg ternary alloying-leaching system

In this work, Si-Ca-Mg alloys were made with different compositions and solidification conditions to investigate the impurity segregation and separation performance from Si, especially for the crucial P impurity at several ppmw levels. Varying acid leaching parameters were also employed to investigate the optimized process window. Results indicate that the novel Si-Ca-Mg alloying-leaching system is valid for high P extraction. The ternary intermetallic phase Ca7Mg7.5±δSi14 appears as the main precipitate in all alloys to gather other minor impurities. Rapid cooling significantly reduced the size of precipitates and Si grain, the impurity segregation was also limited. In the acid leaching experiments, HCl is found as the most economical leaching agents among the studied combinations. Smaller particle size promotes the leaching efficiency, but the increment narrows with increasing Ca/Mg ratio. Leaching kinetics of the studied alloys was found following the modified Kröger-Ziegler model based on a cracking-shrinking mechanism. The impurity purification efficiency increases with increasing Ca/Mg mixing ratio, but significantly reduced by rapid cooling. An analytical model was developed for ternary alloy system to predict the P segregation and its removal with varying alloy concentration through the thermodynamic approach, which shows good agreements of the experimental results.publishedVersio

First-principles study of spin orbit coupling contribution to anisotropic magnetic interaction

Anisotropic magnetic exchange interactions lead to a surprisingly rich variety of the magnetic properties. Considering the spin orbit coupling (SOC) as perturbation, we extract the general expression of a bilinear spin Hamiltonian, including isotropic exchange interaction, antisymmetric Dzyaloshinskii-Moriya (DM) interaction and symmetric $\Gamma$ term. Though it is commonly believed that the magnitude of the DM and $\Gamma$ interaction correspond to the first and second order of SOC strength $$ respectively, we clarify that the term proportional to $\lambda ^{2}$ also has contribution to DM interaction. Based on combining magnetic force theorem and linear-response approach, we have presented the method of calculating anisotropic magnetic interactions, which now has been implemented in the open source software WienJ. Furthermore, we introduce another method which could calculate the first and second order SOC contribution to the DM interaction separately, and overcome some shortcomings of previous methods. Our methods are successfully applied to several typical weak ferromagnets for $3d$, $4d$ and $5d$ transition metal oxides. We also predict the conditions where the DM interactions proportional to $\lambda$ are symmetrically forbidden while the DM interactions proportional to $\lambda ^{2}$ are nonzero, and believe that it is widespread in certain magnetic materials

Effects of Exogenous Melatonin on Body Mass Regulation and Hormone Concentrations in Eothenomys miletus

By regulating the pineal hormone, photoperiods affect many physiological characteristics in small mammals. Thus, melatonin might take part in the thermoregulation of seasonal variations in small mammals. This study determined the influence of melatonin treatment on thermogenic pattern, we measured body mass, thermogenic activities and hormone concentrations of Eothenomys miletus were given exogenous melatonin (MLT) for 28 days. The results shown that body mass was reduced significantly, whereas resting metabolic rate (RMR) and nonshivering thermogenesis (NST) increased at 28 days in MLT group compared to control group as well as the oxidative capacities of mitochondria in liver and brown adipose tissue (BAT) were enhanced; the contents of total and mitochodrial protein increased markedly. Melatonin treatment significantly increased the State 3, State 4 respiration of liver mitochondria, and the activity of cytochrome C oxidase (COX) in liver; but the α-glerocephasphate oxidase (α-PGO) capacity showed no differences during the acclimation in liver. Furthermore, the State 4 respiration, the activities of COX and α-PGO in BAT increased, respectively. The activity of thyroxin 5’-deiodinase ( T45’-DII) in BAT increased remarkably. The serum content of thyroxine (T 4) decreased, and that of tri-iodothyronine (T 3) increased. Moreover, serum leptin levels showed no significant differences in MLT group compared to control group. Together, these data indicate that melatonin enhances thermogenic capacity in E. miletus. Our results suggested that melatonin is potentially involved in the regulation of body mass, adaptive thermogenic capacity and hormone concentrations in E. miletus

Magnon-magnon interaction in monolayer MnBi2_2Te4_4

MnBi$_2$Te$_4$, the first confirmed intrinsic antiferromagnetic topological insulator, have attracted more and more attention in recent years. Here we investigate the energy correction and lifetime of magnons in MnBi$_2$Te$_4$ caused by magnon-magnon interaction. Firstly, a first-principles calculation was performed to get the parameters of the magnetic Hamiltonian of MnBi$_2$Te$_4$. Then the perturbation method of many-body Green's function is applied and the 1st-order self-energy [$\Sigma^{(1)}({\bf k})$] and 2nd-order self-energy [$\Sigma^{(2)}({\bf k},\varepsilon_{\bf k})$] of magnon are obtained. Numerical computation shows that the correction from both $\Sigma^{(1)}({\bf k})$ and $\Sigma^{(2)}({\bf k},\varepsilon_{\bf k})$ are strongly dependent on momentum and temperature, the energy renormalization near Brillouin zone (BZ) boundary is obviously stronger than that near BZ centre. We also find that some dip structures occur in renormalized magnon spectrum near $\rm K$ and $\rm M$ points, and these dip structures should be attributed to $\Sigma^{(2)}({\bf k},\varepsilon_{\bf k})$.Comment: 7 pages, 7 figure