Weak Ferromagnetism in a One-Orbital Double-Exchange Model with Ising Spins for Cerium Oxides

Cerium oxides (ceria) are materials that exhibit weak, room-temperature ferromagnetism without d-electrons. The latter are usually responsible for magnetism in a variety of other oxide compounds, but the underlying mechanism for such a magnetic response in ceria without the d-electrons (d0-magnetism) is still under debate. A possible explanation is Zener double-exchange, where itinerant electrons polarize the localized spins via Hund-coupling as they hop from site to site. Here, we report magnetization and spin-spin correlation results using various values of the Hund-coupling in a one-orbital double-exchange model with Ising spins. In the real material with formula CeO2−x, the oxygen-deficient sites are denoted by x. These sites are related to the density of tetravalent cerium spins (the Ising spin background in our model), which we denoted as and set at N=0.50 in our simulations. Our results at this value of localized spin concentration show ferromagnetic tendencies at low carrier densities (n=0.25). However, ferromagnetism is lost at intermediate carrier concentrations (n=0.50) due to charge localization at high temperatures, as evident from density of states calculations and Monte Carlo snapshots. To our knowledge, our study based on a realistic Zener-type double exchange mechanism is a first in the study of magnetism in cerium oxides. Our results are also consistent with previous studies using similar Hamiltonians in the context of diluted magnetic semiconductors, where Heisenberg spins were used.

PENERAPAN PEMBELAJARAN KOOPERATIF MODEL GROUP TO GROUP EXCHANGE UNTUK MENINGKATKAN HASIL BELAJAR SISWA PADA POKOK BAHASAN SENYAWA HIDROKARBON

This classroom action research generally aimed to improve the quality of learning for 11th grade students of SMAN 2 Jember in the 2018-2019 school year, and especially aimed to improve student learning results through cooperative learning with Group to Group Exchange model on the Hydrocarbon Compounds subject. This research is conducted in two cycles, which each cycle composed of planning, implementation, observation, and reflection. The results of affective value of students were taken from observation sheet, while data of student’s learning outcomes were taken from learning outcomes test. The results of this research showed that (l) The results of affective value of class XI MIPA 4 SMAN 2 Jember on the Hydrocarbon Compounds in cycle 2 experienced an increase, (2) The student learning outcomes of students in 11th grade (XI MIPA 4) SMAN 2 Jember on the Hydrocarbon Compounds increased if compared to the previous year after Group to Group Exchange model was applied. ABSTRAKPenelitian tindakan kelas ini secara umum bertujuan untuk meningkatkan kualitas pembelajaran siswa kelas XI SMAN 2 Jember tahun pelajaran 2018-2019, dan secara khusus untuk mengetahui hasil belajar siswa dengan menggunakan pembelajaran kooperatif model Group to Group Exchange pada pokok bahasan Senyawa Hidrokarbon. Penelitian dilaksanakan dalam dua siklus, dimana masing-masing siklus terdiri dari tahap perencanaan, pelaksanaan, pengamatan, dan refleksi. Data nilai afektif siswa digali dengan lembar observasi, sementara data nilai hasil belajar siswa diambil dari tes hasil belajar. Hasil penelitian menunjukkan bahwa (1) hasil nilai afektif dari siswa kelas XI MIPA 4 pada pokok bahasan Senyawa Hidrokarbon pada siklus 2 mengalami peningkatan, (2) nilai hasil belajar siswa kelas XI MIPA 4 pada pokok bahasan Senyawa Hidrokarbon mengalami peningkatan dibanding tahun pelajaran sebelumnya setelah menggunakan pembelajaran kooperatif model Group to Group Exchange.

Prediction of an ΩbbbΩbbb Dibaryon in the Extended One-Boson Exchange Model

Since Yukawa proposed that the pion is responsible for mediating the nucleon-nucleon interaction, meson exchanges have been widely used in understanding hadron-hadron interactions. The most studied mesons are the σ, π, ρ, and ω, while other heavier mesons are often argued to be less relevant because they lead to short range interactions. However, whether the range of interactions is short or long should be judged with respect to the size of the system studied. We propose that one charmonium exchange is responsible for the formation of the ΩcccΩccc dibaryon, recently predicted by lattice QCD simulations. The same approach can be extended to the strangeness and bottom sectors, leading to the prediction on the existence of ΩΩ and ΩbbbΩbbb dibaryons, while the former is consistent with the existing lattice QCD results, the latter remains to checked. In addition, we show that the Coulomb interaction may break up the ΩcccΩccc pair but not the ΩbbbΩbbb and ΩΩ dibaryons.

Exploring cell membrane water exchange in aquaporin-4-deficient ischemic mouse brain using diffusion-weighted MRI

Background Aquaporin-4 is a membrane channel protein that is highly expressed in brain astrocytes and facilitates the transport of water molecules. It has been suggested that suppression of aquaporin-4 function may be an effective treatment for reducing cellular edema after cerebral infarction. It is therefore important to develop clinically applicable measurement systems to evaluate and better understand the effects of aquaporin-4 suppression on the living body. Methods Animal models of focal cerebral ischemia were created by surgically occluding the middle cerebral artery of wild-type and aquaporin-4 knockout mice, after which multi-b-value multi-diffusion-time diffusion-weighted imaging measurements were performed. Data were analyzed with both the apparent diffusion coefficient (ADC) model and a compartmental water-exchange model. Results ADCs were estimated for five different b value ranges. The ADC of aquaporin-4 knockout mice in the contralateral region was significantly higher than that of wild-type mice for each range. In contrast, aquaporin-4 knockout mice had significantly lower ADC than wild-type mice in ischemic tissue for each b-value range. Genotype-dependent differences in the ADC were particularly significant for the lowest ranges in normal tissue and for the highest ranges in ischemic tissue. The ADCs measured at different diffusion times were significantly different for both genotypes. Fitting of the water-exchange model to the ischemic region data found that the water-exchange time in aquaporin-4 knockout mice was approximately 2.5 times longer than that in wild-type mice. Conclusions Multi-b-value multi-diffusion-time diffusion-weighted imaging may be useful for in vivo research and clinical diagnosis of aquaporin-4-related diseases.

The influence of δ meson on the isospin splitting of in-medium NN → NΔ cross-sections

The isospin splitting of the in-medium [Formula: see text] cross-sections in asymmetric nuclear medium is investigated in the framework of the one-boson exchange model by including [Formula: see text] and [Formula: see text] mesons. Our results show that the medium correction factors [Formula: see text] have [Formula: see text] and [Formula: see text] by using the without-[Formula: see text] sets. By including the [Formula: see text] meson, there appear the totally opposite results in the [Formula: see text] for different channels, i.e., [Formula: see text] and [Formula: see text].