The involvement of astrocytes in brain functions rather than support has been identified and widely concerned. However the lack of an effective stimulation of astrocytes hampers our understanding of their essential roles. Here, we employed 800-nm near infrared (NIR) femtosecond laser to induce Ca2+ wave in astrocytes. It was demonstrated that photostimulation of astrocytes with femtosecond laser pulses is efficient with the advantages of non-contact, non-disruptiveness, reproducibility, and high spatiotemporal precision. Photostimulation of astrocytes would facilitate investigations on information processing in neuronal circuits by providing effective way to excite astrocytes.

Summary In this paper, the electromagnetic efficiency factor is defined to describe the utilization rate of metal conductors in air‐core coils. The geometry‐electromagnetic character and the thermal condition of the coil are coupled to describe the electromagnetic efficiency of the air‐core coils. The geometry‐electromagnetic character is deduced form the inductance computation formula, while the thermal functions are given according to the “Uniformed electrical current density condition” and the “uniformed temperature rise” condition. Curves that reflect the electromagnetic efficiency factor are given while the thermal condition is considered as the mentioned two conditions. The former thermal condition is simpler and is proved to be suitable for midget air‐core coils without complex heat transfer structure or coils with pulse current. While, the latter is proved to be with higher accuracy and can be wildly used in the optimization design of air‐core power reactors. Copyright © 2014 John Wiley & Sons, Ltd.

The direct-current circuit breaker (DCCB) is the most ideal choice for DC fault isolation in DC grids. Despite a late start, China's research and development on the DCCB have made outstanding achievements. This article provides a brief glance of current China's DCCB development status. It begins by sorting out the technical route according to the topology of DCCB. Then it systematically summarises both mechanical and hybrid DCCBs with focussing on the aspects of topology structure and principle, key technology and characteristics, prototype development and application. It is apparent that Chinese scientists and engineers confronted the worldwide problem of large capacity DC breaking, and put forward a comprehensive solution which consists of an innovative topology structure based on coupled negative voltage circuit, breaking throughs on the key technologies such as highly controllable and reliable fault current commutation, millisecond-level ultra-fast and efficient electromagnetic repulsion mechanism, high tolerance and high stability power electronic switch, low residual voltage and fast response energy consumption device, etc. The article states that the world's first set of hybrid high-voltage (HV) DCCB, and the first set of mechanical HV DCCB have been developed. These DCCBs will soon be deployed to the DC grids which have the highest voltage levels therefore require the strongest breaking capacity. These achievements are leading the world in the development and application of DCCB. The article also discusses the overall development trends of DCCB in the areas of new topologies, key technological breakthroughs and application scenarios, etc. These discussions serve as references for DCCB's future technological advancement and its ever-expanding applications. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Abstract:In this paper, taking the minimum metal conductor usage of an air core reactor as optimization goal, the influence of air ducts width and encapsulation number on thermal efficiency and electromagnetic efficiency are analyzed. Combined with the equation constraint conditions for maximum temperature rise conservation, inductance conservation and structure function of reactor considering the change of air ducts width and encapsulation number, the thermal and electromagnetic combined optimization curves are formed, and design results are achieved based on the initial design parameters. Meanwhile, the temperature field simulation model of the reactor is established and the results verify the correctness of the optimization method. According to the design results, the proportionality factor of metal conductor usage is only 0.61 compared with the initial design parameters of the reactor, which shows that the proposed comprehensive optimization method can significantly reduce conductor usage, improving the metal conductor utilization ratio.

Holographic fluorescence imaging is very promising, as it can obtain three-dimensional fluorescence imaging without scanning. However, the current method usually records holograms far from the image plane, with the fluorescence decaying when spreading broadly. Here we show that the signal-to-noise ratio (SNR) of fluorescence holography can be improved by recording the high-contrast interferogram near the image plane. We found that this can be achieved by setting the focal length of the lens for the reference wave (f(2)) close to that for the object wave (f(1)). With experiments, we demonstrate an example of an increase of about 21 times in SNR by changing f(2) from infinity to 226 mm, which is close to f(1) (323 mm).