日层探测

文章介绍了日层探测的概况和研究日层的意义,以及日地空间在空间环境预报中的作用,从日层事件探测实例分析了目前日地空间监测的不足.     

Multidimensional detection of nitroorganic explosives by gas chromatography-pyrolysis-ultraviolet detection

We describe a new methodology for the trace detection of organic explosives containing nitro functionalities. Conventional gas chromatography separates the components of an explosive mixture. Effluent from the gas chromatograph is pyrolyzed by passage over a heated Nichrome wire. Nitric oxide produced on pyrolysis of a nitroorganic compound is then detected by ultraviolet absorption spectroscopy between 180 and 240 nm, using a deuterium lamp as the light source. Nitric oxide exhibits a sharply banded, characteristic spectrum in this region, enabling detection of nitroorganics. The system is tested using the explosive simulants nitrobenzene and 2,4-dinitrotoluene, and with the nitramine explosive tetryl. Detection limits are 25 ng for nitrobenzene and 50 ng for 2,4-dinitrotoluene. Tetryl is detected with a detection limit of 50 ng. The system is both easy to implement and could be built as a compact, low-power device.     

Direct detection of biomolecules in a capillary electrophoresis-chemiluminescence detection system

Direct detection of biomolecules, such as alpha-amino acids, peptides, and proteins, was accomplished using a capillary electrophoresis-chemiluminescence detection system, in which a luminol-hydrogen peroxide-Cu(II)-catalyzed chemiluminescence reaction was utilized. Biomolecules migrated in the capillary, where they mixed with luminol and the Cu(II) catalyst included in the running buffer. The capillary outlet was inserted into a batch-type chemiluminescence detection cell with hydrogen peroxide-supplemented electrolyte solution. Chemiluminescence was observed at the tip of the capillary outlet. The chemiluminescence peak from biomolecules appeared due to the enhancement of Cu(II) catalytic activity for luminol-hydrogen peroxide chemiluminescence. The Cu(II) was more catalytically active when it interacted with biomolecules forming Cu(II)-biomolecule complexes. In this study, biomolecules were directly separated and detected in a capillary electrophoresis-chemiluminescence detection system. Twenty alpha-amino acids, 4 peptides, and 11 proteins were examined. Most of them were detected with satisfactory CL intensity response. Glutamic acid, an alpha-amino acid, was detected at concentrations ranging from 2.0 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.0 x 10(-7) M (0.6 fmol). Glycylglycine, a peptide, was detected at concentrations ranging from 1.7 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.7 x 10(-7) M (0.9 fmol). Hemoglobin, a heme protein, in which the heme structure was independently catalytically active, was detected at concentrations ranging from 1.2 x 10(-7) to 1.0 x 10(-5) M with a detection limit (S/N = 3) of 1.2 x 10(-7) M (0.6 fmol). Representative mixtures of alpha-amino acids and peptides were well detected with superior separation.     

Algebraic change-point detection

Elementary techniques from operational calculus, differential algebra, and noncommutative algebra lead to a new approach for change-point detection, which is an important field of investigation in various areas of applied sciences and engineering. Several successful numerical experiments are presented.     

Spaceborne particle detection

Spaceborne particle detectors occupy a nonnegligible place in basic science research programs. With the general increase of activity in space, and the development of the space industry, the interest in particle detection has become multidisciplinary. The emergence of the notion of space weather is an illustration. The renewed interest of the high-energy physics community in cosmic-ray observation offers new perspectives for detectors. The latest methods and instrumentation developed for particle detection at accelerators have been proposed for a new generation of devices. The current trends are indicated by a brief review of existing, past, and proposed detectors.     

Spatiotemporal heterodyne detection

We describe a scheme in which a camera is turned into an efficient tunable frequency filter of a few-Hertz bandwidth in an off-axis, heterodyne optical mixing configuration, enabling one to perform parallel, high-resolution coherent spectral imaging. This approach is made possible through the combination of a spatial and temporal modulation of the signal to reject noise contributions. Experimental data obtained with dynamically scattered light by a suspension of particles in Brownian motion is interpreted.     

Ultrasensitive leak detection

The objective of this investigation was to develop a method of detecting leaks to a sensitivity of 1.0 × 10^?13 std cm0^?3 s^?1 in vacuum devices and to develop a qualifiable standard leak to provide system calibration at this leak rate. The development work demonstrated that minimum detectable leak rates of 6.5 × 10^?14 and 5.5 × 10^?15 std cm^?3 s^?1 are possible for respective analog and digital measurement modes.     

Single-molecule detection and identification of multiple species by multiparameter fluorescence detection

Two general strategies are introduced to identify and quantify single molecules in dilute solutions by employing a spectroscopic method for data registration and specific burst analysis, denoted multiparameter fluorescence detection (MFD). MFD uses pulsed excitation and time-correlated single-photon counting to simultaneously monitor the evolution of the eight-dimensional fluorescence information (fundamental anisotropy, fluorescence lifetime, fluorescence intensity, time, excitation spectrum, fluorescence spectrum, fluorescence quantum yield, distance between fluorophores) in real time and allows for selection of specific events for subsequent analysis. Using the multiple fluorescence dimensions, we demonstrate a dye labeling scheme of oligonucleotides, by which it is possible to identify and separate 16 different compounds in the mixture via their characteristic pattern by MFD. Such identification procedures and multiplex assays with single-molecule sensitivity may have a great impact on screening of species and events that do not lend themselves so easily to amplification, such as disease-specific proteins and their interactions.     

Multifeature distortion-insensitive constellation detection

Many applications require detection of multiple features that locally remain consistent in shape and intensity characteristics, but may globally change position with respect to one another over time or under different circumstances. We refer to these feature sets, defined by their characteristic relative positioning, as multifeature constellations. We introduce a method of processing in which multiple levels of correlation, using specially designed composite feature detection filters, are used to first detect local features, and then to detect constellations of these local features. We include experimental procedures and results indicating how the use of multifeature constellation detection may be utilized in applications such as sign language recognition and fingerprint matching.     

基于承诺的水印检测协议

提出了基于承诺的水印检测协议.该协议联合使用了随机置换、盲因子、承诺方案和零知识子协议等技术来隐藏水印嵌入位置信息,并采用可信注册机构的签名以保证承诺消息的真实性.该协议可用于证明数字多媒体内容的版权关系而不泄漏任何可用于删除水印的秘密信息,尤其不泄漏水印嵌入位置的信息.而且,协议被证明是零知识的协议.