Rare tau decays from BABAR

The BABAR experiment has now completed data taking and with an integrated luminosity of 531 fb^-1 of e^＋e^- collision data has recorded some 480 million tau-pair events. Various studies of suppressed, rare and forbidden decays of the tau have been conducted, including searches for high-multiplicity decays, for second-class hadronic weak currents, and for lepton-flavour violation.     

区域海、陆、气多圈层作用与灾害预警技术研讨会计算物理学会计算大气物理专业委员会学术年会暨中国现场统计研究会气象、地质统计委员会会议纪要

由计算物理学会计算大气物理专业委员会及中国现场统计研究会气象委员会、中国气科院灾害天气国家重点实验室联合召开的区域海、陆、气多圈层作用与灾害预警技术研讨会,于2009年12月9日—13日在上海召开。会议由两个专业委     

气象武器的物理基础及其军用前景

 气象武器,就是人为地制造、改变和利用地球或大气的状泰.     

国产MEMS陀螺仪MSG7000D实时数据记录系统设计

针对国产MEMS陀螺仪MSG7000D拥有数字输出接口的特点,设计了一种基于FPGA的MSG7000D陀螺仪实时数据记录系统;该系统以FPGA为主控芯片,系统控制模块通过SPI串行通信接口与陀螺仪进行信息交换,从而实现对陀螺仪输出数据的记录、存储;利用三轴位置速率摇摆温控转台对系统设计进行试验论证;试验结果表明,文章设计的MEMS陀螺仪MSG7000D实时数据记录系统有效、实用,为该陀螺仪的后续工程应用奠定了基础,具有一定的工程应用价值。     

用于长期神经电生理记录的自伸展电极阵列

Neural electrodes have been extensively utilized for the investigation of neural functions and the understanding of neuronal circuits because of their high spatial and temporal resolution. However, long-term effective electrophysiological recordings in free-behaving animals still constitute a challenging task, which hinders longitudinal studies on complex brain-processing mechanisms at a functional level. Herein, we demonstrate the feasibility and advantages of using a self-spreadable octopus-like electrode (octrode) array for long-term recordings. The octrode array was fabricated by enwrapping a bundle of eight formvar-coated nickel-chromium microwires with a layer of polyethylene glycol in a custom-made mold. After the electrodeposition of platinum nanoparticles, the microwires at the electrode tip were gathered together and then re-enwrapped with a thin layer of gelatin to maintain their structure and mechanical strength for implantation. Shortly after implantation (within 20 min), the biocompatible gelatin encapsulation swelled and dissolved, causing the self-spreading of the recording channels of the octrode array in the brain. The electrochemical characteristics of the electrode/neural tissue interface were investigated by electrochemical impedance spectroscopy (EIS). Four weeks after implantation, the average impedance of the octrodes (1.26 MΩ at 1 kHz) was significantly lower than that of the conventional tetrodes (1.50 MΩ at 1 kHz, p < 0.05, t-test). Additionally, the octrodes exhibited a better pseudo-capacitive characteristic and a considerably faster ion transfer rate at the electrode interface than the tetrodes. Spontaneous action potentials and local field potentials (LFPs) were also recorded in vivo to investigate the electrophysiological performance of the octrodes. The peak-to-peak spike amplitudes recorded for the octrodes were remarkably larger than those recorded for the tetrodes. The signal quality remained at approximately the same level for the four-week period, while the peak-to-peak spike amplitudes recorded for the tetrodes decreased abruptly. Moreover, the voltage amplitudes recorded by the octrodes at 1–200 Hz were notably larger than those by the tetrodes, suggesting a higher sensitivity in the recording of electrophysiological events. Furthermore, we performed immunochemical analyses on the brain tissues at post-implantation to evaluate the histocompatibility of the electrodes. Tissue responses of the octrodes were alleviated considerably, evidenced by the reduced astroglial intensity and increased neuron density around the implant site as compared to the tetrodes, which may be due to the relatively small size of each decentralized recording channel after self-spreading in vivo. Generally, the fabricated octrodes exhibited a lower electrochemical impedance value at the octrode/neural tissue interface and an increased signal quality during the long-term electrophysiological recording in freely moving mice as compared to the conventional tetrodes. All of these are desirable characteristics in neural circuit dissections in vivo.     

基于碳纳米材料的神经电极技术

As a powerful tool for monitoring and modulating neural activities, implantable neural electrodes constitute the basis for a wide range of applications, including fundamental studies of brain circuits and functions, treatment of various neurological diseases, and realization of brain-machine interfaces. However, conventional neural electrodes have the issue of mechanical mismatch with soft neural tissues, which can result in tissue inflammation and gliosis, thus causing degradation of function over chronic implantation. Furthermore, implantable neural electrodes, especially depth electrodes, can only carry out limited data sampling within predefined anatomical regions, making it challenging to perform large-area brain mapping. With excellent electrical, mechanical, and chemical properties, carbon-based nanomaterials, including graphene and carbon nanotubes (CNTs), have been used as materials of implantable neural electrodes in recent years. Electrodes made from graphene and CNT fibers exhibit low electrochemical impedance, benefiting from the porous microstructure of the fibers. This enables a much smaller size of neural electrode. Together with the low Young's modulus of the fibers, this small size results in very soft electrodes. Soft neural electrodes made from graphene and CNT fibers show a much-reduced inflammatory response and enable stable chronic in vivo action potential recording for 4-5 months. Combining different modalities of neural interfacing, including electrophysiological measurement, optical imaging/stimulation, and magnetic resonance imaging (MRI), could leverage the spatial and temporal resolution advantages of different techniques, thus providing new insights into how neural circuits process information. Transparent neural electrode arrays made from graphene or CNTs enable simultaneous calcium imaging through the transparent electrodes, from which concurrent electrical recording is taken, thus providing complementary cellular information in addition to high-temporal-resolution electrical recording. Transparent neural electrodes from carbon-based nanomaterials can record well-defined neuronal response signals with negligible light-induced artifacts from cortical surfaces under optogenetic stimulation. Graphene and CNT-based materials were used to fabricate MRI-compatible neural electrodes with negligible artifacts under high field MRI. Simultaneous deep brain stimulation (DBS) and functional magnetic resonance imaging (fMRI) with graphene fiber electrodes in the subthalamic nucleus (STN) in Parkinsonian rats revealed robust blood oxygenation level dependent responses along the basal ganglia-thalamocortical network in a frequency-dependent manner, with responses from some regions not previously detectable. This review introduces the recent development and application of neural electrode technologies based on graphene and CNTs. We also discuss biological safety issues and challenges faced by neural electrodes made from carbon nanomaterials. The use of carbon-based nanomaterials for the fabrication of various soft and multi-modality compatible neural electrodes will provide a powerful platform for both fundamental and translational neuroscience research.     

(Ce,Cu)∶LiNbO3晶体非挥发全息记录理论研究与优化

根据双中心带输运模型,对(Ce,Cu)∶LiNbO3晶体双中心非挥发全息记录进行了理论研究与优化。推导了(Ce,Cu)∶LiNbO3晶体的微观参量,采用数值方法通过严格求解模拟双中心带输运方程来模拟全息记录过程。分析了记录过程中,记录与敏化光强、Ce和Cu掺杂浓度以及晶体微观参量对(Ce,Cu)∶LiNbO3晶体双中心全息记录的影响。发现(Ce,Cu)∶LiNbO3晶体非挥发全息记录中实现高衍射效率与固定效率的主导因素是深中心Cu,在记录过程中,深中心Cu建立起了很强的空间电荷场。数值模拟的结果经过实验验证,最高饱和与固定衍射效率别为60.5%和53.8%。     

高密度数字光存储技术

 随着信息科学的迅速发展,对存储介质的存储密度和存储容量的要求在不断提高,然而传统的信息存储方法已几乎接近物理极限,于是寻找新的存储介质和存储方法就成为近年来信息科学的研究热点。光存储技术是继磁存储技术之后的又一新兴技术,它利用光改变物质物理或者化学性质存储信息,近年来不仅取得了重大的技术突破,而且形成了一个庞大的产业。现在以光盘为代表的光学数字数据存储技术已成为信息存储中不可缺少的载体。与以往的磁存储相比,光盘存储的优点是存储容量大、密度高、寿命长、信息的信噪比高,可以非接触式读写和擦除等。     

磁控溅射法制备的高反Ag5In5Te47Sb33相变薄膜的光谱性质及短波长 …

研究了磁控溅射制备的Ａｇ５Ｉｎ５Ｔｅ４７Ｓｂ３３相变薄膜的光谱及短波长静态记录性能，研究结果表明，晶态薄膜反射率较高，并在６００～９００ｎｍ波长范围内，晶态与非晶态的反射率和折射率相差很大，在ＣＤ－Ｅ系统的工作波长７８０ｎｍ处，晶态反射率高达５０％，光学常数为５．３４－１．０ｉ；非晶态反射率为２３％，光学常数为２．５－１．０３ｉ，从这一角讲，Ａｇ５Ｉｎ５Ｔｅ４７Ｓｂ３３相变薄膜适于做ＣＤ－Ｅ系统的