A novel spin-valley-coupled nodal-ring semimetal in single-layer Ta2C3.

Nodal-ring semimetals with band crossing are the new type of quantum materials that have attracted considerable interest from scholars for research. In general, the spin-orbit coupling (SOC) effect opens a band gap at the Dirac point. Therefore, finding 2D nodal-ring semimetals with resistance to SOC has more challenges. Based on first-principles calculations, we propose here that the two-dimensional (2D) Ta2C3 monolayer is a novel nodal-ring semimetal. In particular, Ta2C3 forms six closed rings in the Brillouin zone (BZ) with SOC, which originates from the dxy,x2-y2 orbitals of Ta and the pz orbitals of C. The nodal-ring bands at the K point in Ta2C3 exhibits characteristics of valley splitting and spin polarization due to the breaking of inversion symmetry and SOC. The masximal spin-splitting at the K point is as large as 268.87 meV and 61.90 meV for the conduction band minimum (CBM) and valence band maximum (VBM), respectively. The massless Dirac fermions in the non-equivalent valley have the opposite Berry curvature and spin moment. Therefore, 2D Ta2C3 is novel spin-valley-coupled nodal-ring semimetal. In addition, we found interesting negative differential resistance effects when calculating its transport properties. Our results not only provide an ideal platform for studying the combination of new physical properties, spintronics and valleytronics, but also open the way for designing low-power and fast-transport electronic devices.

[Radioprotective effect of rmIL-12 on mice irradiated by γ-ray].

The aim of this study was to investigate the radioprotective effect of recombinant murine interleukin 12 (rmIL-12) on mice irradiated by γ-ray. Fifty- six BALB/c mice were totally irradiated by 6.0 Gy of (60)Co γ-ray and randomly divided into irradiation control group,rmIL-12 treated group and recombinant murine thrombopoietin (rmTPO) treated group.The 5 and 20 µg/kg of rmIL-12 were administrated intraperitoneally at 24 h before irradiation respectively (low and high dose rmIL-12 treated group), 15 µg/kg of rmTPO was administrated subcutaneously at 30 min and 24 h following irradiation in rmTPO treated group. The general conditions of mice were observed twice a day, the changes in body weight and peripheral blood cell counts were examined once every three days, bone marrow cells were collected to perform colony cultivation at day 14 and 28 after irradiation. The results showed that the general conditions of mice in rmIL-12 treated group were better than those in irradiation control group. Compared with the irradiation control group,5 and 20 µg/kg rmIL-12 treatment significantly promoted platelet recovery, resulting in less profound nadirs (15.9% vs 8.1%,18.2% vs 8.1%,P < 0.01) and rapid recovery to normal levels (11 days vs 14 days). WBC count recovery rate in rmIL-12 treated group was faster than that in the irradiation control group. The WBC and platelet count recovery rate in 5 µg/kg rmIL-12 treated group were as fast as that in the rmTPO treated group, both of which were slower than that in 20 µg/kg rmIL-12 treated group (P > 0.05). Semi-solid bone marrow cell culture also demonstrated that rmIL-12 could stimulate bone marrow cells to form more CFU-Mix than those in the irradiation control group in vitro at day 14 and 28 after irradiation(P < 0.01).There was no significant difference between rmIL-12 and rmTPO treated groups (P > 0.05), CFU-GM counts in 5 µg/kg rmIL-12 treated group and rmTPO treated group at day 28 after irradiation were higher than those in irradiation control group(P < 0.05), but less than those in 20 µg/kg rmIL-12 treated group (P < 0.05). It is concluded that rmIL-12 has a significant radioprotective effect on mice irradiated by γ-ray.

[Therapeutic effect of rmIL-12 combined with G-CSF on acute radiation sickness produced by γ-ray irradiation in mice].

The aim of this study is to observe the therapeutic effect of recombinant murine interleukin 12 (rmIL-12) combining with granulocyte colony stimulating factor (G-CSF) on mice irradiated by γ-rays. 56 BALB/c mice were totally irradiated by 6.0 Gy of (60)Co γ-ray and randomly divided into irradiation control group, rmIL-12 treatment group, G-CSF treatment group and combination therapy (rmIL-12 plus G-CSF) group. rmIL-12 20 µg/kg was administrated intraperitoneally at 1 h following irradiation, and was administrated every 3 days after irradiation for 4 times in rmIL-12 treatment group. G-CSF 100 µg/kg was administrated subcutaneously the 2 h following irradiation for 14 d in G-CSF treatment group. The dose and method of rmIL-12 and G-CSF in combination therapy group were same as in rmIL-12 group and G-CSF group. The general status of mice were observed twice a day, the changes in body weight, peripheral blood cell (WBC and Plt) counts were examined once every three days, bone marrow cells were collected to perform colony cultivation on day 14 and 28 after irradiation. The results showed that WBC count recovery time in combination therapy group was significantly earlier than that of the control group (7 d vs 11 d), WBC count recovery velocity in the combination therapy group was no significant different from that of the G-CSF treatment group. Combined therapy significantly promoted Plt count recovery, resulting in less profound nadirs (16.5% vs 8.1%, P < 0.01) and rapid recovery to normal levels (11 d vs 14 d), Plt count recovery velocity in the combination therapy group was no significant different from that of the rmIL-12 treatment group. Culture of bone marrow cells in semi-solid medium also demonstrated that combination of rmIL-12 and G-CSF could stimulate bone marrow cells to form more CFU-GM and CFU-Mix than those of the irradiation control group in vitro on day 14 and 28 after irradiation (P < 0.05). It is concluded that the combination of rmIL-12 and G-CSF can significantly accelerate the recovery of hematopoietic function in mice with acute radiation sickness.