Exchange bias behavior of monodisperse Fe3O4/γ-Fe2O3 core/shell nanoparticles

We have carried out systematic studies on well-characterized monodisperse Fe₃O₄/γ-Fe₂O₃ core/shell nanoparticles of 2-30 nm having a very narrow size distribution and possessing a uniquely mono-layer of surface γ-Fe₂O₃. This unique core-shell structure, probably having a disordered magnetic surface state, leads us to three key observations of unusual magnetic properties: i) a very large magnetic exchange anisotropy reaching over 7 × 10⁶ erg/cm³ for the smaller particles, ii) exchange bias behavior in the magnetization data of the core/shell Fe₃O₄/γ-Fe₂O₃ nanoparticles, and iii) the temperature dependence of the coercive field following an unusual exponential behavior.     

LD-pumped passively Q-switched Nd:YVO4/YVO4 laser with an Nd3+:Cr4+:YAG saturable absorber

By using a piece of codoped Nd³⁺:Cr⁴⁺:YAG crystal as a saturable absorber, a laser-diode pumped passively Q-switched Nd:YVO₄/YVO₄ laser has been realized. The maximum laser output power of 2.452 W has been obtained at the incident pump power of 8.9 W for an 8.8% transmission of the output coupler at 1064 nm, corresponding to a slope efficiency of 30%. The other output laser characteristics of the laser have also been investigated. The laser with a Nd³⁺:Cr⁴⁺:YAG saturable absorber has a lower threshold pump power and a higher slope efficiency compared to that with a similar small-signal transmission of a Cr⁴⁺:YAG saturable absorber.     

Spin polarization in parallel double dots with spin-orbit interaction

Spin polarization in parallel double quantum dots embedded in arms of Aharonov-Bohm interferometer is investigated. The spin-orbit interaction exists in quantum dots. We find that the spin polarization is quite large even with a weak spin-orbit interaction. The direction and the strength of the spin polarization are well controllable and manipulatable by simply varying the strength of spin-orbit interaction or the energy levels in quantum dots. Moreover, electron-electron interaction strengthens the spin accumulation when the energy levels of the two quantum dots are identical. As the energy levels are unequal, electron-electron interaction cannot increase the spin accumulation. It is worth mentioning that the device is free of a magnetic field or a ferromagnetic material and it can be easily realized with present technology.     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

Joint remote preparation of an arbitrary three-qubit state via EPR-type pairs

In this work, we propose a scheme to realize a joint remote preparation of an arbitrary three-qubit state using six EPR-type pairs as the shared quantum resource. By determining the right measurement bases for the preparers and right ancilla-assisted unitary transformation/recovery operations for the receiver, our scheme applies to the most general case when all the coefficients of the state to be prepared and the EPR-type pairs are complex. The total success probability is found to be dependent only on the “smaller” coefficients of the EPR-type pairs shared between the receiver and one of the preparers.     

Rashba自旋-轨道相互作用对一维谐振子势场中电子性质的影响

分析了Rashba自旋-轨道相互作用对一维谐振子势场中电子性质的影响,发现该自旋-轨道相互作用能够导致能级之间的自旋翻转,并且自旋翻转的性质明显依赖于自旋-轨道耦合系数和参考系坐标之间的关系.     

重频XeF蓝绿激光技术

 利用表面放电光泵浦技术,研制了重频XeF(C-A)激光器,运行频率达到10 Hz。研究了运行频率、气体流量对激光输出能量稳定性的影响,分析了影响输出稳定性的主要因素,实验结果表明,提高气流量可有效改善重频输出能量的稳定性。同时,还给出了优化实验条件下不同运行频率连续20个脉冲较为理想的输出结果。运行频率分别为1,2,5 Hz时,输出能量稳定性较好,输出能量大于4.0 J;气流量大于53 L/s时,10 Hz重频运行的输出稳定性已显著提高,平均输出能量也达到1.8 J。     

Evolution of the field quantum entropy and entanglement in a system of multimode light field interacting resonantly with a two-level atom through Nj-degenerate NΣ-photon process

The time evolution of the field quantum entropy and entanglement in a system of multi-mode coherent light field resonantly interacting with a two-level atom by degenerating the multi-photon process is studied by utilizing the Von Neumann reduced entropy theory, and the analytical expressions of the quantum entropy of the multimode field and the numerical calculation results for three-mode field interacting with the atom are obtained. Our attention focuses on the discussion of the influences of the initial average photon number, the atomic distribution angle and the phase angle of the atom dipole on the evolution of the quantum field entropy and entanglement. The results obtained from the numerical calculation indicate that: the stronger the quantum field is, the weaker the entanglement between the quantum field and the atom will be, and when the field is strong enough, the two subsystems may be in a disentangled state all the time; the quantum field entropy is strongly dependent on the atomic distribution angle, namely, the quantum field and the two-level atom are always in the entangled state, and are nearly stable at maximum entanglement after a short time of vibration; the larger the atomic distribution angle is, the shorter the time for the field quantum entropy to evolve its maximum value is; the phase angles of the atom dipole almost have no influences on the entanglement between the quantum field and the two-level atom. Entangled states or pure states based on these properties of the field quantum entropy can be prepared.     

采用单边大光腔结构改善电吸收调制器的光场分布

设计并制备了具有单边大光腔结构的半导体电吸收(electroabsorption，EA)调制器.模拟和测试的结果均表明：单边大光腔结构能有效地改善EA调制器的光场分布，使椭圆形的近场光斑变得圆形化，从而达到与圆形模式光纤之间的匹配，有利于提高耦合效率.     

动生、感生电动势与法拉第电磁感应定律等价性的研究

法拉第电磁感应定律与动生电动势、感生电动势之和是完全等价的。本文通过实例证明,等价是有条件的。当回路中存在大块导体时,则不等价。