基于FPGA的VME总线控制器及其驱动程序

本文论述了用于兰州重离子加速器冷却储存环(HIRFL-CSR)前端控制系统的总线控制器的FPGA设计及其基于ARM-Linux下的驱动程序设计。该总线控制器采用Altera公司的ACEX系列中的EP1K30实现,通过VME总线背板同其它VME设备(CPLD)通信,可读VME设备数据,监视电源运行状况,也可向VME设备发送命令和写数据,并且能够响应VME设备中断,读中断数据。为了能够通过AT91RM9200控制器访问VME总线控制器,必须为其编写相应的驱动程序。驱动程序定义了应用程序调用接口和数据格式,并实现了中断机制、多进程访问和数据的突发(burst)读写。

基于MSP430F149型单片机的智能温度控制系统

介绍了以MSP430F149单片机为核心的一个智能温度控制系统。介绍了如何利用MSP430F149本身的优点并结合相关的外部电路实现键盘输入、实时监测、自动温度控制和调节的控制系统的方法。重点阐述了系统的硬件构成、各部分的主要作用及系统软件的设计过程。由于本模块对输入量同时采用硬件和软件的非线性补偿,故具有精度高、可靠性较好、电路简单、成本低、体积小、生产调试方便等特点。

High-order harmonic generation and multi-photon ionization of Na-2 in laser fields

In this paper high-order harmonic generation (HHG) spectra and the ionization probabilities of various charge states of small cluster Na-2 in the multiphoton regimes are calculated by using time-dependent local density approximation (TDLDA) for one-colour (1064 nm) and two-colour (1064 nm and 532 nm) ultrashort (25 fs) laser pulses. HHG spectra of Na2 have not the large extent of plateaus due to pronounced collective effects of electron dynamics. In addition, the two-colour laser field can result in the breaking of the symmetry and generation of the even order harmonic such as the second order harmonic. The results of ionization probabilities show that a two-colour laser field can increase the ionization probability of higher charge state.

A Semi-Quantitative Analysis of Essential Micronutrient in Folium Lycii Using Laser-Induced Breakdown Spectroscopy Technique

In this paper, the capabilities of laser-induced break down spectroscopy (LIBS) for rapid analysis to multi-component plant are illustrated using a 1064 nm laser focused onto the surface of folium lycii. Based on homogeneous plasma assumption, nine of essential micronutrients in folium lycii are identified. Using Saha equation and Boltzmann plot method electron density and plasma temperature are obtained, and the irrelative concentration (Ca, Mg, Al, Si, Ti, Na, K, Li, and Sr) are obtained employing a semi-quantitative method.

DG指数在定量多样性时的缺陷及其内涵解析

生物多样性通常使用物种丰富度、Simpson指数、Shannon-Wiener多样性指数等来进行度量,但是在土壤动物群落研究中,由于使用了粗水平的分类方法,因此即使生境变化很大,这些多样性指数在评估群落多样性变化时仍然是不适当的。为了克服这种限制,廖崇惠(1990,2009)提出用DG指数来代替这些标准的多样性指数,并在土壤动物生态学领域得到了广泛应用。然而笔者分析发现DG指数与Pielou均匀度指数呈显著的负相关关系(r=–0.534,P=0.000),即,高的均匀度反而有低的多样性。另外,DG指数与类群数(r=0.648,P=0.000)和类群密度(r=0.487,P=0.000)呈明显的正相关,类群数的下降可以通过部分类群密度的上升而获得补偿,群落的类群丢失后却可以获得一个不变的甚至更高的多样性值。因此,笔者不支持DG指数用于测度生物多样性,提议使用各类群实际群势与潜在群势比值的平均值来估计群落潜在多度的实现程度。如果继续使用DG指数作为实际生境条件的一个指标,那么与以往不同,DG指数测度的是该生境群落多度增长的一种潜力。

根系吸水机理研究进展

植物根系除支撑和固定其地上部这一力学功能外的一个重要功能就是从土壤中吸收水分和养分以满足植物地上部生长所需.表征植物根吸水能力的一个重要的水力学参数是水力导度(用单位时间单位面积的水流速率来表示),可在细胞(细胞水力导度)、单根和整株根系水平上来表达,其中单根导度可分为径向导度和轴向导度,仅径向导度反映了单根吸收水分的能力,而轴向导度则反映了植物根系输导水分的能力,但在整株根系水平上则以通过整个根系的水流通量与根木质部和根表土壤间的水势差之比来表示,既包括径向导度也包括轴向导度.近年来,对植物根系吸水或根水力导度研究已取得了许多重要进展,这对阐明根系吸水机理和地上地下部关系起到了重要作用.下面做一简要综述.1　根系吸收水分的主要部位根系吸水的部位一般认为在距根尖10～100ｍｍ的区域内,这种看法是基于解剖上的证据.从根表面到根中心,依次为根表皮、下表皮、皮层、内皮层、中柱,其中根表皮是有最高吸收活性的根区,但一般仅可存活几天,而内皮层将皮层和中柱分开形成了根内侧的一个界面,老根一般有周皮或栓质化的内皮层,有很强的不透水性(即阻力很大).但Ｓａｎｄｅｒｓｏｎ[1]对大麦的研究发现,虽然老根区内重度栓化的内皮层已...

优化农业结构推进我国农业现代化进程

２０年前，中国科学院在湖南的桃源、河北的栾城和黑龙江的海伦开始了建立农业现代化综合科学实验基地的工作。第一步是在这三个县进行农业自然资源综合考察和制订农业现代化建设的基本战略和设想。当时这三个县所制订的农业现代化建设基本战略和设想中，都把建立合理的农...

Surface-enhanced Raman scattering of 4-aminothiophenol self-assembled monolayers in sandwich structure with nanoparticle shape dependence: Off-surface plasmon resonance condition

A universal metal-molecule-metal sandwich architecture by the self-assembly of Ag nanoparticles (NPs) and Au NPs of various shapes interconnected with 4-aminothiophenol (4-ATP) molecules was presented. These Ag NPs/4-ATP/Au NPs sandwich structures were characterized by surface enhanced Raman scattering (SERS) using an off-surface plasmon resonance condition. Enhancement factors (EF) on the order of 10(8) for 9b(b(2)) vibration mode were observed for the 4-ATP self-assembled monolayers (SAMs) in such sandwich structures. The factors are 2 orders of magnitude larger than that on the monolayer of Au NPs of various shapes under similar condition. More importantly, remarkable increase in the intensity of b(2) vibrational modes, which is characteristic of the charge transfer (CT) behavior between metal NPs and 4-ATP molecules, was observed in these sandwich structures under 1064 nm excitation. The obtained EF on these sandwich structure for 9b(b(2)) is larger than that for 7a vibration mode by a factor of similar to 10(2), demonstrating the importance of the contribution of the CT mechanism and the CT behavior of metal contacts, which play a significant role in metal-molecule-metal nanosystems.

Synthesis of REF3 (RE = Nd, Tb) nanoparticles via a solvent extraction route

NdF3 and TbF3 nanoparticles were successfully synthesized via a solvent extraction route using Cynex923 (R3P=O). X-ray diffraction (XRD) study showed that pure hexagonal phase NdF3 and pure orthorhombic phase TbF3 could be obtained under the current synthetic conditions. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations indicated that as-obtained NdF3 nanoplates have a diameter of 50-80 nm and thickness of 10-20 nm and TbF3 products have sphere morphologies with diameter from 70 to 170 nm. The driving force for the growth of NdF3 nanoplates could be attributed to the hexagonal crystal structure. The luminescence properties of NdF3 and TbF3 nanoparticles were investigated, which indicated that NdF3 nanoparticles showed typical emission at 888,1064, and 1328 nm and TbF3 nanoparticles showed characteristic emission of Tb3+ (f-f).

Structure and identity of 4,4 '-thiobisbenzenethiol self-assembled monolayers

Self-assembled monolayers (SAMs) of 4,4'-thiobisbenzenethiol (TBBT) can be formed on Au surface spontaneously. The structural characteristics and adsorption behavior of TBBT SAMs on Au have been investigated by surface enhanced Raman scattering (SERS), electrochemical cyclic voltammetry (CV), ac impedance spectroscopy (EIS), and atomic force microscopy (AFM). It is demonstrated that TBBT adsorbed on Au by losing a H atom, forming one Au-S bond, and the other mercapto group is free at the surface of the monolayer owing to the presence of the nu(S-H) at 2513 cm(-1) and the delta(C-S-H) at 910 cm(-1) in SERS. The enhancement of the vibration of C-S (1064 cm(-1)), the aromatic C-H vibration (3044 cm(-1)), and the absence of the vibration of S-S illustrate TBBT adsorbed on Au forming a monolayer with one benzene ring tilted with respect to the Au surface. The interpretation of the observed frequencies is aided by ab initio molecular orbital (MO) calculations at the HF/6-31G* level of theory. Electrochemical CV and EIS indicate TBBT monolayers can passivate the Au effectively for its low ratio of pinhole defects (theta = 99.6%). AFM studies give details about the surface morphology. The applications of TBBT SAMs have been extensively investigated by exposure of Cu2+ ion to TBBT SAMs on Au and covalent adsorption of metal nanoparticles.

Surface-enhanced Raman scattering of silver-gold bimetallic nanostructures with hollow interiors

Surface-enhanced Raman scattering (SERS) activity of silver-gold bimetallic nanostructures (a mean diameter of similar to 100 nm) with hollow interiors was checked using p-aminothiophenol (p-ATP) as a probe molecule at both visible light (514.5 nm) and near-infrared (1064 nm) excitation. Evident Raman peaks of p-ATP were clearly observed, indicating the enhancement Raman scattering activity of the hollow nanostructure to p-ATP. The enhancement factors (EF) at the hollow nanostructures were obtained to be as large as (0.8 +/- 0.3)x10(6) and (2.7 +/- 0.5)x10(8) for 7a and 19b (b(2)) vibration mode, respectively, which was 30-40 times larger than that at silver nanoparticles with solid interiors at 514.5 nm excitation. EF values were also obtained at 1064 nm excitation for 7a and b(2)-type vibration mode, which were estimated to be as large as (1.0 +/- 0.3)x10(6) and (0.9 +/- 0.2)x10(7), respectively. The additional EF values by a factor of similar to 10 for b(2)-type band were assumed to be due to the chemical effect. Large electromagnetic EF values were presumed to derive from a strong localized plasmas electromagnetic field existed at the hollow nanostructures.

溶液pH对硫堇与DNA相互作用方式的影响

用电化学和光谱方法研究了溶液pH对硫堇(TH)与小牛胸腺脱氧核糖核酸(CT-DNA)相互作用方式的影响。电化学测量结果表明,在pH 7.2的磷酸盐缓冲溶液中,TH与CT-DNA之间的作用方式以嵌入结合为主,在pH6.5的磷酸盐缓冲溶液中,TH与CT-DNA之间的作用方式既存在嵌入结合也存在静电作用。荧光光谱测量结果表明,TH与DNA结合后其荧光发生猝灭,通过Stern-Volmer方程计算得到pH 6.5时TH-DNA体系的猝灭常数高于pH 7.2时的值,表明在pH 6.5的溶液中两者相互作用更强。圆二色谱(CD)实验结果也证实了这一结论。

Host-guest-like thiamine-anion complexation in thiaminium bis(tetrafluoroborate)

In the title compound, 3-[(4-amino-2-methyl-5-pyrimidin-1-io)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium(2+) bis(tetrafluoroborate), C12H18N4OS2+. 2BF(4)(-), the divalent thiamine cation (in the F conformation) is associated with BF4- anions via two characteristic bridging interactions between the thiazolium and pyrimidinium rings, i.e. C-H . . . BF4- . . . pyrimidinium and N-H . . . BF4- . . . thiazolium interactions. Thiamine molecules are linked by N-H . . .O hydrogen bonds to form a helical chain structure.