橘红素经PI3K/Akt/mTOR信号通路调控胃癌细胞BGC-823和SGC-7901的增殖和凋亡

目的探讨橘红素对胃癌细胞BGC-823和SGC-7901的自噬作用及其机制。方法不同浓度橘红素(7.5、15、30、60、120μmol/L)处理两株细胞后,CCK-8法检测其吸光度值,计算细胞增殖抑制率;流式细胞仪检测细胞凋亡水平;用60μmol/L浓度的橘红素处理后通过细胞划痕法检测两种细胞迁移能力;Western blotting法检测自噬相关蛋白p62、凋亡蛋白Bax、Bcl-2及PI3K/Akt/mTOR信号通路相关蛋白表达的影响。结果与对照组相比,橘红素处理组增殖、迁移能力显著下降(P<0.01),细胞凋亡数增加,自噬蛋白p62的表达浓度依赖性升高(P<0.05),凋亡蛋白Bax表达增加(P<0.05),Bcl-2表达下降(P<0.05),磷酸化的p-Akt和p-mTOR的表达水平显著降低(P<0.05)。结论橘红素可通过抑制PI3K/Akt/mTOR信号通路调控SGC-7901和BGC-823细胞的增殖和凋亡,并可抑制其自噬。

High repetition granular Co/Pt multilayers with improved perpendicular remanent magnetization for high-density magnetic recording

Thanks to the strong perpendicular magnetic anisotropy(PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magnetic storage.However, reversed magnetic domains come into being with the increasing layer repetition ‘N’ to reduce magneto-static energy, resulting in the remarkable diminishment of the remanent magnetization(Mr). As a result, the product of Mrand thickness(i.e., the remanent moment-thickness product, Mrt), a key parameter in magnetic recording for reliable data storing and reading, also decreases dramatically. To overcome this issue, we deposit an ultra-thick granular [Co/Pt]80multilayer with a total thickness of 68 nm on granular SiNxbuffer layer. The Mrt value, Mrto saturation magnetization(Ms) ratio as well as out of plane(OOP) coercivity(Hcoop) are high up to 2.97 memu/cm^(2), 67%, and 1940 Oe(1 Oe = 79.5775 A·m^(-1)),respectively, which is remarkably improved compared with that of continuous [Co/Pt]80multilayers. That is because large amounts of grain boundaries in the granular multilayers can efficiently impede the propagation and expansion of reversed magnetic domains, which is verified by experimental investigations and micromagnetic simulation results. The simulation results also indicate that the value of Mrt, Mr/Msratio, and Hcoopcan be further improved through optimizing the granule size, which can be experimentally realized by manipulating the process parameter of SiNxbuffer layer. This work provides an alternative solution for achieving high Mrt value in ultra-thick Co/Pt multilayers, which is of unneglectable potential in applications of high-density magnetic recording.

医学院校基础-临床桥梁学科教学现状与改革

基础-临床桥梁学科是医学生学习基础医学与临床医学之间的衔接阶段,这类学科具有相同的特征即较强的理论性与实践性。就现况而言,这类桥梁学科在教学上存在有学科设置、教师培训、教学效果、考核内容等方面的不足。本文将结合实际阐述桥梁学科的教学现况并提出教学改革的措施,为指导基础-临床桥梁学科的教学实践提供新的思路。

Broad-Band FMR Linewidth of Co_2MnSi Thin Films with Low Damping Factor:The Role of Two-Magnon Scattering

The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonMity of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.

Magnetization-direction-dependent inverse spin Hall effect observed in IrMn/NiFe/Cu/YIG multilayer structure

The magnetization-direction-dependent inverse spin Hall effect(ISHE) has been observed in NiFe film during spin Seebeck measurement in IrMn/NiFe/Cu/yttrium iron garnet(YIG) multilayer structure, where the YIG and NiFe layers act as the spin injector and spin current detector, respectively. By using the NiFe/IrMn exchange bias structure, the magnetization direction of YIG(MYIG) can be rotated with respect to that of NiFe(MNiFe) with a small magnetic field, thus allowing us to observe the magnetization-direction-dependent inverse spin Hall effect voltage in NiFe layer. Compared with the situation that polarization direction of spin current(σs) is perpendicular to MNiFe, the spin Seebeck voltage is about 30% larger than that when σs and MNiFe are parallel to each other. This phenomenon may originate from either or both of stronger interface or bulk scattering to spin current when σs and MNiFe are perpendicular to each other. Our work provides a way to control the voltage induced by ISHE in ferromagnets.

The origin of spin current in YIG/nonmagnetic metal multilayers at ferromagnetic resonance

Spin pumping in yttrium-iron-garnet（YIG）/nonmagnetic-metal（NM） layer systems under ferromagnetic resonance（FMR） conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2（NM_1 =Cu or Al,NM_2 =Pt or Ta）,we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface（in contact with thin YIG）,either due to the magnetic proximity effect（MPE） or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect（ISHE）.The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on.

Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

The spin transparency at the normal/ferromagnetic metal （NM/FM） interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect （SHE） in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect （ISHE） in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents （σsc）, the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electro-chemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 （Py） than that of Ni is obtained from the nonlocal voltage measurements.

Probing the magnetization switching with in-plane magnetic anisotropy through field-modified magnetoresistance measurement

Effective probing current-induced magnetization switching is highly required in the study of emerging spin-orbit torque(SOT)effect.However,the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process,or the non-electric approach of Kerr imaging technique.Here,we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field.In this case,the symmetry of MR is broken,resulting in a resistance difference for opposite magnetization orientations.Moreover,the feasibility of our method is widely evidenced in heavy metal/ferromagnet(Pt/Ni_(20)Fe_(80) and W/Co_(20)Fe_(60)B_(20))and the topological insulator/ferromagnet(Bi_(2)Se_(3)/Ni_(20)Fe_(80)).Our work simplifies the characterization process of the in-plane magnetization switching,which can promote the development of SOT-based devices.

Structural and Magnetic Properties of Co2MnSi Thin Film with a Low Damping Constant

Co2MnSi thin films are made by magnetron sputtering onto MgO （001） substrates. The crystalline quality is improved by increasing depositing temperature and/or annealing temperature. The sample deposited at 550℃ and subsequently annealed at 550℃ （sample I） exhibits a pseudo-epitaxial growth with partially ordered L21 phase. Sample I shows a four-fold magnetic anisotropy, in addition to a relatively weak uniaxial anisotropy. The Gilbert damping factor of sample I is smaller than 0.001, much smaller than reported ones. The possible reasons responsible for the small Gilbert damping factor are discussed, including weak spin-orbit coupling, small density of states at Fermi level, and so on.