Tunneling magnetoresistance in diluted magnetic semiconductor tunnel junctions

Using the spin-polarized tunneling model and taking into account the basic physics of ferromagnetic semiconductors, we study the temperature dependence of the tunneling magnetoresistance (TMR) in the diluted magnetic semiconductor (DMS) trilayer heterostructure system (Ga,Mn)As/AlAs/(Ga,Mn)As. The experimentally observed TMR ratio is in reasonable agreement with our result based on the typical material parameters. It is also shown that the TMR ratio has a strong dependence on both the itinerant-carrier density and the magnetic ion density in the DMS electrodes. This can provide a potential way to achieve larger TMR ratio by optimally adjusting the material parameters.Comment: 5 pages (RevTex), 3 figures (eps), submitted to PR

Structure and electronic properties of the (3×3\sqrt{3}\times \sqrt{3})R30∘R30^{\circ} SnAu2_2/Au(111) surface alloy

We have investigated the atomic and electronic structure of the ($\sqrt{3}\times \sqrt{3}$)$R30^{\circ}$ SnAu$_2$/Au(111) surface alloy. Low energy electron diffraction and scanning tunneling microscopy measurements show that the native herringbone reconstruction of bare Au(111) surface remains intact after formation of a long range ordered ($\sqrt{3}\times \sqrt{3}$)$R30^{\circ}$ SnAu$_2$2/Au(111) surface alloy. Angle-resolved photoemission and two-photon photoemission spectroscopy techniques reveal Rashba-type spin-split bands in the occupied valence band with comparable momentum space splitting as observed for the Au(111) surface state, but with a hole-like parabolic dispersion. Our experimental findings are compared with density functional theory (DFT) calculation that fully support our experimental findings. Taking advantage of the good agreement between our DFT calculations and the experimental results, we are able to extract that the occupied Sn-Au hybrid band is of (s, d)-orbital character while the unoccupied Sn-Au hybrid bands are of (p, d)-orbital character. Hence, we can conclude that the Rashba-type spin splitting of the hole-like Sn-Au hybrid surface state is caused by the significant mixing of Au d- to Sn s-states in conjunction with the strong atomic spin-orbit coupling of Au, i.e., of the substrate.Comment: Copyright: https://journals.aps.org/authors/transfer-of-copyright-agreement; All copyrights by AP

UCL OpenFOAM Course Notes 2019

The UCL OpenFOAM Course was initiated by the Department of Mechanical Engineering, totally free and registered under UCL doctoral school. It aims to popularise OpenFOAM among research students and help beginners to get through the initial painful stage dealing with the unfamiliar operation environment, also an excellent chance to exchange simulation skills and generate collaborations. In 2019, the course was held during 26-28 June, with our lecturers and 55 students attended. It was fantastic to see so many conversations getting started, and to feel that our UK/London community is getting stronger. We received very positive feedback, and more importantly, strong interests from worldwide users who wanted but could not join us in London. Thereby, this document is published online to demonstrate what we have taught. We hope this will be helpful for a wider audience. In Chapter 1-4, we present step-by-step guideline for installing/using/understanding OpenFOAM; subsequently, our Appendixes provides advanced tutorials for various purposes

Secretion dynamics of soyasaponins in soybean roots and effects to modify the bacterial composition

Soyasaponins are triterpenoid saponins widely found in legume plants. These compounds have drawn considerable attention because they have various activities beneficial for human health, and their biosynthesis has been actively studied. In our previous study, we found that legume plants including soybean secrete soyasaponins from the roots in hydroponic culture throughout the growth period, but the physiological roles of soyasaponins in the rhizosphere and their fate in soil after exudation have remained unknown. This study demonstrates that soyasaponins are secreted from the roots of field-grown soybean, and soyasaponin Bb is the major soyasaponin detected in the rhizosphere. In vitro analysis of the distribution coefficient suggested that soyasaponin Bb can diffuse over longer distances in the soil in comparison with daidzein, which is a typical isoflavone secreted from soybean roots. The degradation rate of soyasaponin Bb in soil was slightly faster than that of daidzein, whereas no soyasaponin Bb degradation was observed in autoclaved soil, suggesting that microbes utilize soyasaponins in the rhizosphere. Bacterial community composition was clearly influenced by soyasaponin Bb, and potential plant growth-promoting rhizobacteria such as Novosphingobium were significantly enriched in both soyasaponin Bb-treated soil and the soybean rhizosphere. These results strongly suggest that soyasaponin Bb plays an important role in the enrichment of certain microbes in the soybean rhizosphere

Children on the Move in China: Insights from the Census Data 2000–2020

Using data from the 2000, 2010, and 2020 National Population Census of China, this study uncovers evolving trends in the experiences of children in family structures reshaped by China's massive internal migration. We develop a new framework to examine family structures from the census data, which facilitates a detailed exploration of family splits as a result of migration. Our results show a significant surge in the proportion of children in migrant families and the trend of children on the move. While the number of left-behind children far exceeded that of migrant children in 2000, the picture became the opposite in 2020, signifying an enhanced capacity and inclination for migrant parents to bring their children to migration destinations. This shift has also engendered a more heterogeneous population of children in migrant families. Notably, a subgroup warranting particular attention is that of “left-behind child migrants,” those moving to proximate towns or cities without both parents. This emergence blurs the traditional urban–rural dichotomies and underscores the intricacies of a family split within the migrant population. Finally, we reflect on the significant role of educational aspirations and obstacles that influence these migratory patterns