Localized electrical nerve blocking

Localized electrical nerve blocking was investigated in computer simulation and in vivo trials for sinusoidal frequencies between 5 and 20 kHz. Computer simulations indicated that a localized transmission block of the axons could occur in each of the axon models. An approximation of nerve stimulation was derived from individual axon simulations conducted over axon diameters of 5-15 microm and electrode to axon distances of 0.25 to 2.0 mm. Examination of the membrane voltage and ionic gate potentials indicated that the block could be attributed to an elevated membrane voltage. The elevated membrane voltage could prevent conduction of action potentials through the region of the sinusoidal currents. At lower amplitudes, the sinusoidal current could stimulate the axon and generate a continuous series of action potentials. In vivo trials demonstrated that the sinusoidal frequencies of greater than 10 kHz would cause a localized block in rats. Sinusoidal frequencies below 5 kHz would lead to a reduction in muscle force that appeared to be caused by depletion of transmitter at the neuromuscular junction. As indicated by the computer models of rat nerves, the endplate depletion block occurred at a lower frequency (below 5 kHz) than the block (above 10 kHz). A partial block of the axon was demonstrated, suggesting that sinusoidal currents could be used to provide selective stimulation if they are combined with distal electrical stimulation.     

不同的思维——苹果公司的Mac Mini电脑

苹果电脑公司把大量的计算能力都塞进了小巧玲珑的Mac Mini电脑中。苹果电脑公司经过仔细设计的Mac Mini是一个性能优越的、低噪声的、经济的计算机,但大小只有6．5英寸×6．5英寸×2英寸、重量不足3磅。想更深入地了解下面介绍的这些模块的特性,请访问www．edn．com/051216pe。感谢Other World Computing公司(www．otherowrldcomputing．com)提供的本篇报道所使用的高分辨率图片。     

Motion measurement errors and autofocus in bistatic SAR.

This paper discusses the effect of motion measurement errors (MMEs) on measured bistatic synthetic aperture radar (SAR) phase history data that has been motion compensated to the scene origin. We characterize the effect of low-frequency MMEs on bistatic SAR images, and, based on this characterization, we derive limits on the allowable MMEs to be used as system specifications. Finally, we demonstrate that proper orientation of a bistatic SAR image during the image formation process allows application of monostatic SAR autofocus algorithms in postprocessing to mitigate image defocus.     

Role of PbSe Structural Stabilization in Photovoltaic Cells

Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC films during processing. Here, an improvement in long‐range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer‐scale rearrangement of PbSe NCs during ligand exchange, improving the long‐range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fission solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface‐bound chloride ions, reduced sub‐bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts.     

用于照明设备的高亮度LED驱动

随着高亮度(HB)LED效率的不断提高,即流明/瓦特(Lm/W)比的增加,越来越多的照明应用开始选择高亮度LED,例如汽车的外灯(日间行车灯,近光灯、远光灯)和普通照明设备等。LED生产厂家最近推出的高亮度LED的效率已经超过80Lm/W。因此,在照明设备中可以利用LED替换传统的卤素灯,例如MR16聚光灯。从传统的卤素灯过渡到高亮度LED可以大大降低功耗,     

单一5V电源高速放大器针对高分辨率视频而优化

人们不断要求视频运算放大器用更少的资源做更多的事情,就像要求设计这些放大器的优良设计师一样.为了实现更高的视频分辨率,需要更高的模拟视频信号带宽,因而需要更快的运算放大器.同时,设计师们还在不停地寻找以更低的电压甚至是单电源轨来实现更高分辨率的方法.     

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Buried‐channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10⁵ cm² V^?1 s^?1) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top‐gate of a dopant‐less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10¹¹cm^?2, light effective mass (0.09m_e), and high effective g‐factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low‐disorder material platform for hybrid quantum technologies.     

Fully Printed Organic Electrochemical Transistors from Green Solvents

To achieve the full potential of scalable and cost‐effective organic electronic devices, developments are being made in both academic and industry environments to move toward continuous solution‐processing techniques that make use of safe and environmentally benign “green” solvents. In this work, the first example of a transistor device that is fully solution processed using only green solvents is demonstrated. This achievement is enabled through a novel multistage cleavable side chain process that provides aqueous solubility for semiconducting conjugated polymers, paired with aqueous inkjet printing of PEDOT:PSS electrodes, and a solution deposited ion gel electrolyte as the dielectric layer. The resulting organic electrochemical transistor devices operate in accumulation mode and reach maximum transconductance values of 1.1 mS at a gate voltage of ? 1 V. Normalizing the transconductance value to the channel dimensions yields g_m/W = 2200 S m^?1 (µC* = 22 F cm^?1 V^?1 s^?1), making these devices suitable for a range of applications requiring small signal amplification such as transistors, biosensors, and ion pumps. This new material design and device process paves the way toward scalable, safe, and efficient production of organic electronic devices.     

Monitoring hacker activity with a Honeynet

The Honeynet Project was founded by 30 US based security professionals with the intention of researching the techniques, tools, tactics and motives of hackers and the ‘blackhat’ community in general. A Honeynet Project is an all volunteer, non‐profit organization committed to sharing and learning the motives, tools, and tactics of the hacking community. It is comprised of a number of information security professionals dedicated to honeynet research and information security. This paper outlines the technical configuration of a honeynet, presents some of the key attacks on the honeynet to date and provides recommendations for securing networked systems. Copyright © 2005 John Wiley & Sons, Ltd.     

On the integration of SIC and MIMO DoF for interference cancellation in wireless networks

Recent advances in MIMO degree-of-freedom (DoF) models allowed MIMO research to penetrate the networking community. Independent from MIMO, successive interference cancellation (SIC) is a powerful physical layer technique used in multi-user detection. Based on the understanding of the strengths and weaknesses of MIMO DoF and SIC, we propose to have DoF-based interference cancellation (IC) and SIC help each other so that (i) precious DoF resources can be conserved through the use of SIC and (ii) the stringent SINR threshold criteria can be met through the use of DoF-based IC. In this paper, we develop the necessary mathematical models to realize the two ideas in a multi-hop wireless network. Together with scheduling and routing constraints, we develop a cross-layer optimization framework with joint DoF IC and SIC. By applying the framework on a throughput maximization problem, we find that SIC and DoF IC can indeed work in harmony and achieve the two ideas that we propose.