Measuring the Fundamental Parameters of Hot Hydrogen－Rich White Dwarfs

This review considers the observations of hot, hydrogen-rich white dwarf stars, with particular reference to measurements of temperature, surface gravity and composition. Spectroscopic data from a variety of wavelength ranges are required for this work and, in particular, the important contributions from optical, ultraviolet and extreme ultraviolet studies are discussed. Using the values of Tefr and log g determined for an individual white dwarf, estimates of mass and radius might be derived from the theoretical mass-radius relation. The issue of the accuracy of the theoretical mass-radius calculations and the prospects for making empirical tests using observational data are outlined.     

The Hercules Échelle Spectrograph at Mt. John

The High Efficiency and Resolution Canterbury University Large échelle Spectrograph (HERCULES) a fibre-fed échelle spectrograph that was designed and built at the University of Canterbury and has been in operation at Mt. John University Observatory since April 2001.HERCULES receives light from the f/13.5 Cassegrain focus of the 1 m McLellan telescope. Resolving powers of R = 41 000, 70 000 and 82 000 are available. An R2 200 × 400 mm échelle grating provides dispersion and cross-dispersion uses a large BK7 prism in double pass. The wavelength coverage is designed to be 380–880 nm in a single exposure. The maximum detective quantum efficiency of the fibre, spectrograph and detector system is about 18% in 2 arc second seeing. High wavelength stability (to better than 10 ms^-1 in radial velocity) is achieved by installing the whole instrument in a large vacuum tank at 2–4 torr and by there being no moving parts. The tank is in a thermally isolated and insulated environment. The paper describes the design philosophy of HERCULES and its performance during the first year of operation. Now deceased; formerly at This revised version was published online in July 2006 with corrections to the Cover Date.     

双光子湮灭吸收截面和吸收系数

双光子湮灭造成的γ射线吸收是γ射线天文学辐射转移理论的一个重要内容。通过相对论变换，将目前QED理论给出的仅在动量中心参考系中表示的双光子湮灭截面推广到实验室系（观测者系），并用湮灭前两光子的能量hw,hw‘及夹角θ表示此截面，便于γ射线在天文学中的实际应用。进一步，在各向同性周边辐射场的一般前提下，求出方向平均的简化截面公式σ（w,w‘），得出方向平均的湮灭阈值条件和湮灭概率最大时两个光子能量的匹配条件。进一步确认在γ射线天文学中，双光子湮灭截面和γ光子－电子的康普顿散射截面确有可比性。最后完成了天体物理中几种常见低频辐射场如热韧致辐射场、黑体辐射场以及非热的幂律场中双光子湮灭吸收系数krr(hw)-hw的计算曲线，并给出较详细的物理讨论。     

The nature of iron and manganese species in dam waters

The molecular weight (M. W.) distributions of iron and manganese species in dam water samples were investigated by use of gel filtration, while the ion-exchangeable and non-ion-exchangeable fractions of these metals were also analysed by ion-exchange chromatography. For the samples studied, more than 96 per cent of the manganese species present were found to be ion-exchangeable, whilst less than 35 per cent of iron species were ion-exchangeable. These results correlated with the finding that all the manganese species had molecular weights less than 700, but that the molecular weights of the iron species were mostly in excess of 5000. Electron paramagnetic resonance (EPR) spectroscopy has been used to support the finding that manganese is almost totally present in the form of simple aquated Mn(II) ions.     

曲线桥梁摩擦滑移隔振试验及隔振机理研究

针对曲线桥梁在地震中因固定支座处及桥墩底部受力过大而破坏严重的现象,提出考虑支座摩擦滑移隔震的曲线桥梁抗震设计方法,通过大型振动台模型试验,研究曲线桥梁考虑支座摩擦滑移时的隔震机理。试验结果表明:支座摩擦滑移可有效减小地震作用下曲线桥梁的桥墩加速度响应,但同时会增加桥墩与梁体间的相对位移;曲线桥梁进行隔震设计后,桥墩的应变响应明显减小,证明该设计方法可有效避免地震作用下桥墩底部产生较大的损伤;最后,探讨了考虑支座摩擦滑移时曲线桥梁的隔震机理并与震害进行了对比验证。研究成果可为曲线桥梁的减震隔设计提供新的视角。     

Phosphorus retention in constructed wetlands enhanced by zeolite- and clinopyroxene-dominated lava sand

Constructed wetlands (CWs) are engineered systems for treating wastewater by sequestering nutrients and contaminants. Our aim was to assess the main phosphorus (P) binding states in operating CWs to assess P saturation and indications on P recycling potential of filter materials, which might be necessary under future peak P scenarios. The investigated vertical flow CWs (operation time up to 16 years) are based on either fluviatile (Fluv) sand or zeolite- (Ze-LS) and clinopyroxene (Cl-LS)-dominated lava sand. Organic and inorganic P accumulated in all CWs independent of filter materials and showed a considerable increase with operation time. Concentrations of P decreased sharply with depth in the Fluv-CWs compared to only a slight decrease in the lava sand CWs, with P concentrations of deeper horizons approximating the relatively P enriched original lava sand substrates. Orthophosphate was the dominant pool in all CWs, while the sum of organic fractions ranged between 11% and 33%. Sequential extraction indicated that P was mainly associated with Fe and Al (hydr)oxides for Fluv-CWs and Ze-LS-CWs, while Ca and Mg bound mineral phosphates dominated in Cl-LS-CWs. Oxalate extractions pointed to a clear dominance of P fractions associated with poorly crystalline Fe- and Al-(oxy)hydroxides. Solution ³¹P NMR analyses revealed that inositol hexakisphosphates were a major pool of organic P in surface layers of CWs, which increased with operation time. With a maximum of 0.5% P content, filter sands do not appear to be a suitable fertilizer for direct application to agricultural fields. The dominance of inorganic, poorly crystalline P species point to potentially high desorption capacity which might be investigated further, to assess recycling potential of P or usage of filter materials as soil amendments with relatively high plant available P. The latter might become feasible and economically attractive under future P scarcity. Simultaneously, P saturation indexes (DPS) did not indicate an imminent P saturation of filters, since P accumulation was not restricted by binding to Al and Fe minerals.     

湘东丘陵区4种林地深层土壤溶解性有机碳的数量和光谱特征

选取湘东丘陵4种典型母质发育的林地土壤,挖掘土壤剖面并分层采集土壤样品至母质层/母岩,研究深层土壤有机碳（SOC）和溶解性有机碳（DOC）的数量和分布规律,采用紫外-可见光谱技术分析深层土壤DOC的宏观化学结构特征。结果表明,土壤DOC含量（2.33~185.26 mg·kg^-1）在板岩红壤和酸性紫色土剖面上某些深层土层出现升高现象。DOC/SOC除第四纪红土红壤在浅层表土最高（1.5%）外,其他3种土壤均在60~80 cm深层土层达到最高峰值（1.0%~2.5%）。SOC数量是控制不同母质土壤DOC数量的重要因素。但光谱分析显示,随着土壤剖面的加深,DOC的宏观化学组成、结构趋于复杂,化学稳定性升高。尽管一些深层土层中DOC/SOC升高,但其DOC化学结构更为复杂,评价深层土壤SOC和DOC稳定性还应考虑其化学结构特性。     

Measurement of IO radical concentrations in the marine boundary layer using a cavity ring-down spectrometer

An open-path cavity ring-down spectroscopy (CRDS) instrument for measurement of atmospheric iodine monoxide (IO) radicals has been tested in the laboratory and subsequently deployed in Roscoff on the north-west coast of France as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project in September 2006. In situ measurements are reported of local IO mixing ratios in the marine boundary layer. To obtain these mixing ratios, accurate absorption cross sections of IO are required at the selected wavelengths used for spectroscopic measurements. Absorption cross sections at the bandheads of the IO A²Π_3/2–X²Π_3/2 (3,0) and (2,0) vibronic bands were thus verified by a combination of spectral simulation methods, inter-comparison of prior determinations of cross-sections at high and low spectral resolution, and by measurement of rates of loss of IO by its self-reaction. The performance of the open-path CRDS instrument was tested by measuring concentrations of NO₂ in ambient air, both within and outside the laboratory, with results that were in excellent agreement with a previously validated continuous wave CRDS apparatus for NO₂ detection. During the RHaMBLe campaign, the open-path CRDS instrument was located within a few metres of the shoreline and operated at wavelengths close to 435 nm to detect the absorption of light by trace levels of IO. The IO mixing ratios were obtained on two days, peaked close to low tide, and were approximately 5–10 times higher than values calculated from column densities previously reported by long-path, differential optical absorption spectroscopy (DOAS) in coastal regions. The typical detection limit of the instrument was estimated to be 10 pptv of IO, with some fluctuation around this value depending on the conditions of wind and atmospheric aerosol particles, and the total accumulation time was 30 s for each data point. The observations of relatively high concentration of IO, compared to the values previously reported by DOAS, are consistent with the concurrent observations using a LIF (Laser induced Fluorescence) instrument (Whalley et al. in press). The first such measurements of localized IO by CRDS and LIF should contribute to an improved understanding of the chemistry of halogen compounds and the formation of iodine oxide aerosol particles in the marine boundary layer.     

P350微色谱柱在线分离富集-火焰原子吸收光谱法测定矿石中痕量金

在王水介质条件下,用自行设计的微色谱柱在线分离富集系统分离富集矿石样品中的痕量金,采用火焰原子吸收光谱法进行测定。在原子吸收光谱仪吸喷溶液的流路上,用P350微色谱柱研究了金的分离富集条件,采用快速吸附和快速洗脱技术,以盐酸溶液为淋洗液,亚硫酸钠溶液为洗脱液,测定一个样品整个分离和测定过程仅需1 min,成功地克服了火焰原子吸收光谱法测定金灵敏度低的缺点。方法的相对标准偏差小于3.2%,检出限为0.078μg/g。与现行离线分离富集方法相比,建立的方法具有高效、快速、成本低廉的优点,经实际样品验证获得了较为满意的结果。