添加纳米TiO2的氯醚树脂的XPS分析

在紫外线老化前后,利用光电子能谱(XPS)研究了分别添加金红石型和锐钛型纳米TiO2的氯醚树脂。研究发现,氯醚树脂中氯、氧元素具有表面富积现象——趋肤效应,而钛和碳元素在内层聚集;添加颜料粒子越小,在表面含量越大;金红石型纳米二氧化钛紫外屏蔽性好,减缓树脂老化;而锐钛型纳米二氧化钛具有显著的光催化活性,加速树脂老化。因此,金红石型纳米二氧化钛将是一种有前途的紫外线吸收剂。     

Spectrophotometric pH measurement in estuaries using thymol blue and m-cresol purple

The conditional acid dissociation constants (pK_a′) of two sulfonephthalein dyes, thymol blue (TB) and m-cresol purple (mCP), were assessed throughout the estuarine salinity range (0<S<40) using a tris/tris–HCl buffer and spectrophotometric measurement. The salinity dependence of the pK_a′ of both dyes was fitted to the equations (25 °C, total proton pH scale, mol kg soln⁻¹):

The estimated accuracy of pH measurements using these calculated pK_a′ values is considered to be comparable to that possible with careful use of a glass electrode (±0.01 pH unit) but spectrophotometric measurements in an estuary have the significant advantage that it is not necessary to calibrate an electrode at different salinities. pH was measured in an estuary over a tidal cycle with a precision of ±0.0005 pH unit at high (S>30) salinity, and ±0.002 pH unit at low (S<5) salinity. The pH increased rapidly in the lower salinity ranges (0<S<15) but less rapidly at higher salinities.     

氮气、氧气和空气水合物的合成及其拉曼光谱特征

在-20℃和不同的压力下,在实验室内分别合成了氮气水合物(16MPa)、氧气水合物(13MPa)和空气水合物(15MPa),并对其N—N和O—O键伸缩振动的拉曼光谱特征进行了研究。结果表明,人工合成的水合物中的N—N和O—O键的拉曼位移与天然的空气水合物中的数据十分接近。在氮气水合物和空气水合物中,N—N键的拉曼峰值均为2322.4cm-1;O—O键的拉曼峰值在氧气水合物和空气水合物保持一致,均为1547.8cm-1。空气水合物分解的拉曼谱图表明,它不是氮气水合物和氧气水合物组成的混合物,而是由氮分子和氧分子共同生成的单一水合物,氮分子和氧分子同时进入水合物的大笼和小笼中。与空气中的氮、氧比例相比,水合物中氧分子明显富集,氮分子和氧分子的比例为2.4∶1。     

The project “spice”

Proposed to both the French and the European Space Agency as one possible small mission, SPICE is a project for a dedicated small satellite for a near-IR spectroscopic all-sky survey. The instrument would cover the spectral range 1.8 - 3.6µm, possibly extended to 1.8 - 7µm, at a resolution of 100, with pixels of 1 arc-min. The excellent sensitivity (0.02 MJy sr-1) results from: i) the quasi-zero level of background due to the efficient passive cooling of the whole experiment; ii) the use of large format arrays; iii) the non-stop observing mode (drift-scanning). The spectral domain, complementing the one of ISO, partially opaque from the ground, is specially rich in spectral features tracing stars and all components of the Interstellar Medium (molecular, atomic and ionized gas, dust). With a cooling below 80 K of the focal instrument, then it becomes possible to consider doubling the spectral domain and to cover the whole 1.8 - 7µm range.     

ISIS IR: The first infrared fibre-fed spectrograph

ISIS IR is the first attempt to use fibre optics for near infrared spectroscopy (1.8m). It is a field spectrograph (2D spectroscopy), and can work at various resolving powers (up to 25000). It can be transported anywhere, and soon it will be used at CFHT with one NICMOS 3-based camera.Département d'Astrophysique Extragalactique et de Cosmologie     

The development of radio astronomy at Hartebeesthoek

The development of radio astronomy at the Hartebeesthoek Radio Astronomy Observatory in South Africa is described. The Hartebeesthoek site was established originally by NASA as one of three Deep Space Stations equipped with 26-m parabolic reflector antennas. It was first used for radio astronomy by South Africa in terms of the NASA host nation agreement which allowed for its use at times when the facility was not needed for its primary purpose of tracking space probes. After NASA withdrew from South Africa in 1975, the South African Council for Scientific and Industrial Research took over the site and the 26-m parabolic reflector antenna, which NASA had abandoned in position, and established it as a national observatory. The development of the facility to the stage where it could support a variety of observing programmes such as continuum observations and mapping, spectroscopy and pulsar timing is described as well as the role played by the Observatory in global programmes of very long baseline interferometry.     

X-ray spectroscopy of stellar coronae

Summary From the early discovery in 1948 of X-rays from the Solar corona, X-ray spectroscopy has proven to be an invaluable tool in studying hot astrophysical and laboratory plasmas. Because the emission line spectra and continua from optically thin plasmas are fairly well known, high-resolution X-ray spectroscopy has its most obvious application in the measurement of optically thin sources such as the coronae of stars. In particular X-ray observations with theEINSTEIN observatory have demonstrated that soft X-ray emitting coronae are a common feature among stars on the cool side of the Hertzsprung-Russell diagram, with the probable exception of single very cool giant and supergiant stars and A-type dwarfs. Observations with the spectrometers aboardEINSTEIN andEXOSAT have shown that data of even modest spectral resolution (/ = 10–100) permit the identification of coronal material at different temperatures whose existence may relate to a range of possible magnetic loop structures in the hot outer atmospheres of these stars. The higher spectral resolution of the next generation of spectrometers aboard NASA'sAXAF and ESA'sXMM will allow to fully resolve the coronal temperature structure and to enable velocity diagnostics and the determination of coronal densities, from which the loop geometry (i.e. surface filling factors and loop lengths) can be derived. In this paper various diagnostic techniques are reviewed and the spectral results fromEINSTEIN andEXOSAT are discussed. A number of spectral simulations forAXAF andXMM, especially high-resolution iron K-shell, L-shell, and2s-2p spectra in the wavelength regions around 1.9 Å, 10 Å, and 100 Å, respectively, are shown to demonstrate the capabilities for temperature, density, and velocity diagnostics. Finally, iron K-shell spectra are simulated for various types of detectors such as microcalorimeter, Nb-junction, and CCD.     

The effect of thermal treatment on the 57Fe Mössbauer spectrum of beryl

Mössbauer spectra (MS) of blue, green and yellow beryl (ideally Be₃Al₂Si₆O₁₈) containing approximately 1% of iron were obtained at 295 and 500 K. Room temperature (RT) spectra of both blue and green samples showed the presence of an asymmetric Fe²⁺ doublet (ΔE _Q~2.7 mm/s, δ~1.1 mm/s), with a very broad low-velocity peak. There is no clear evidence for the presence of a ferric component. The MS of the yellow sample at RT consists of an intense central absorption with parameters typical for Fe³⁺ (ΔE _Q~0.4 mm/s, δ~0.29 mm/s), plus an apparently symmetrical Fe²⁺ doublet. This sample acquires a light-blue shade upon heating in air at about 620 K. Thermal treatments at high temperatures caused no significant changes in the MS, but the green and yellow beryl acquire a blue colour. All these results are interpreted in relation to the existence of channel water and the distribution of iron among the available crystallographic sites.     

Synchrotron IR study of hydrous ringwoodite (γ-Mg2SiO4) up to 30 GPa

High-pressure synchrotron infrared (IR) absorption spectra were collected between 650 and 4,000 cm⁻¹ at ambient temperature for hydrous Mg-ringwoodite (γ-Mg₂SiO₄) up to 30 GPa. The main feature in the OH⁻ stretching region is an extremely broad band centred at 3,150 cm⁻¹. The hydrogen bond is strong for most protons and the most probable site for protonation is the tetrahedral edge. With increasing pressure, this band shifts downward while decreasing its integrated intensity until disappearance at a pressure of 25 GPa. Only one band at 2,450 cm⁻¹ and an absorption plateau persist with a maximum wavenumber of 3,800 cm⁻¹. This behaviour is reversible upon pressure release. We interpret this as a second-order phase transition occurring in hydrated Mg-ringwoodite at high pressure (beyond ∼ 25 GPa). This result is compatible with the observation by Kleppe et al. (Phys Chem Miner 29:473–476, 2002a) who suggested the presence of Si–O–Si linkages and/or partial increase in the coordination of Si. Beyond the phase transition, the protons are delocalized and their environment on the ringwoodite structure is probably quite different from that at low pressure. Data obtained in situ at high pressures and temperatures are needed to better understand the effect of protonation on the structure and to better constrain this phase transition.     

笼状水合物拉曼光谱特征与结构水合数的耦合关系

为了探讨不同气体组分和环境介质对形成笼状结构类型水合物和水合数的影响, 开展了一元体系 (CH4、CO2、C3H8 )和二元体系(CH4 +CO2、CH4 +C3H8、CH4 +N2 )的水合物生成结晶充填过程、结晶构型和动力学特性分析, 并对生成的水合物进行了拉曼光谱分析。结果表明单组分甲烷充填小孔穴 512和大孔穴 512 62 形成Ⅰ型笼状结构水合物(SⅠ), 二氧化碳和丙烷只占据大孔穴 512 64 形成Ⅱ型笼状结构水合物 (SⅡ ); 而二元混合组分中小孔穴中只充填有甲烷, 而没有CO2、N2 和C3H8。应用反褶积的ν1 对称谱带测定了CH4 分子在Ⅰ型结构大孔穴和小孔穴中的相对占有率,并根据谱带的面积比(对应于小孔穴与大孔穴)计算了平衡条件下甲烷水合物孔穴占有率及其耦合的水合数, 认为气体分子的大小不仅影响它所充填的孔穴形态和类型, 而且影响水合物生成的结构类型和水合数。