Platinum-Group Element Geochemical Certified Reference Materials (GPt1-7)

Unlike the situation for other elements, few reference materials certified for the platinum-group elements are currently available. Therefore, the GPt1-7 series of PGE geochemical CRMs, prepared by the IGGE, represent an important addition and comprise a range of matrix types, including a soil, stream sediment, Mg-rich ultramafic rock, Fe-rich ultramafic rock, platinoid ore depleted in Cu, Ni and Fe, and a chromitite. The concentration of PGE in these samples ranges over 4-5 orders of magnitude and the samples were shown to have good homogeneity as assessed by a variance test. Analytical methods based on different principles were used in sample certification, including several fire assay and wet chemical procedures used for decomposition and preconcentration. Certified values for the elements Pt, Pd, Os, Ru, Ir, Rh and Au were determined by AAS, catalytic colourimetry (COL), catalytic polarography (POL), atomic emission spectrometry (AES), ICP-MS and NAA. Recently, the GPt1-7 samples were approved as national primary CRMs by the State Bureau of Technical Supervision of China.     

GIS在1∶5万榆关镇幅区域地质调查中的应用

讨论ＧＩＳ系统在１∶５万区调中的应用,阐述ＧＩＳ系统在区调过程中对各种资料的处理与编辑,包括野外资料的采集、图层的划分及图形与图像图件的编制。建立了榆关镇幅综合信息库。     

用SAVQ技术实现太阳射电频谱的数据压缩

对自适应矢量量化（SAVQ）技术在太阳射电频谱数据压缩中的应用进行了有意义的讨论．给出一种压缩比和失真可调的SAVQ压缩方法,指出提高数据压缩比的有效方法之一为样本集成,同时介绍了用该技术对北京天文台太阳射电频谱仪上的两个波段（1．0GHz－2．0GHz和2．6GHz－3．8GHz）的观测数据进行压缩的实用效果,并与国际同行所用的ICON方式进行性能比较．最后展示了数据压缩技术及其在天文上的应用．     

Solar EUV line identifications from delayed beam-foil spectra

A number of electric dipole transitions from low-lying long-lived levels in Si-, P- and S-like ions of Fe and neighbouring elements have been identified by their longevity in delayed EUV spectra after foil excitation of fast ion beams. Some of these new identifications pertain to previously unidentified lines in solar flare spectra.     

C-type shocks in the interstellar medium: profiles of CH+ and CH absorption lines

We have computed optical absorption-line profiles of CH⁺ and CH, as predicted by a model of a C-type shock propagating in a diffuse interstellar cloud. Both these species are produced in the shock wave in the reaction sequence that is initiated by C⁺(H₂, H)CH⁺. Whilst CH⁺ flows at the ion speed, CH, which forms in the dissociative recombination reaction CH⁺₃(e⁻, H₂)CH, flows at a speed which is intermediate between those of the ions and the neutrals. The predicted velocity shift between the CH⁺ and CH line profiles is found to be no more than approximately 2 km s⁻¹, which is smaller than has previously been assumed. We also investigate OH and HCO⁺, finding that the correlation between their column densities, recently observed in the diffuse interstellar medium, can be reproduced by the model.     

Semi-automated extraction of digital objective prism spectra

We describe a method for the extraction of spectra from high-dispersion objective prism plates. Our method is a catalogue-driven plate solution approach, making use of the right ascension and declination coordinates for the target objects. In contrast to existing methods of photographic plate reduction, we digitize the entire plate and extract spectra off-line. This approach has the advantages that it can be applied to CCD objective prism images and spectra can be re-extracted (or additional spectra extracted) without having to re-scan the plate. After a brief initial interactive period, the subsequent reduction procedure is completely automatic, resulting in fully reduced, wavelength-justified spectra. We also discuss a method of removing stellar continua using a combination of non-linear filtering algorithms.   The method described is used to extract over 12 000 spectra from a set of 92 objective prism plates. These spectra are used in an associated project to develop automated spectral classifiers based on neural networks.     

Foreground separation methods for satellite observations of the cosmic microwave background

A maximum entropy method (MEM) is presented for separating the emission resulting from different foreground components from simulated satellite observations of the cosmic microwave background radiation (CMBR). In particular, the method is applied to simulated observations by the proposed Planck Surveyor satellite. The simulations, performed by Bouchet &38; Gispert, include emission from the CMBR and the kinetic and thermal Sunyaev–Zel'dovich (SZ) effects from galaxy clusters, as well as Galactic dust, free–free and synchrotron emission. We find that the MEM technique performs well and produces faithful reconstructions of the main input components. The method is also compared with traditional Wiener filtering and is shown to produce consistently better results, particularly in the recovery of the thermal SZ effect.     

Precise laboratory wavelengths of the Mg I and Mg II resonance transitions at 2853, 2803 and 2796 Å

Strong ultraviolet resonance transitions are observed routinely both in the Galactic interstellar medium and in quasar absorption systems. The quality of the astronomical spectroscopic data now available demands more precise laboratory rest wavelengths. Of particular interest is the accuracy with which one can constrain space–time variations in fundamental constants using quasar spectra. A recent analysis by Webb et al. of 25 quasar spectra using Mg and Fe transitions tentatively suggests that the fine-structure constant was smaller at earlier epochs. To permit a check on this result, and to allow further more extensive investigations, we have carried out a new determination of the laboratory wavelengths of Mg  i  2853 Å, Mg  II  2796 Å and Mg  II  2803 Å by high-resolution Fourier transform spectroscopy. Our results for Mg  II  2796 Å are consistent with the value measured independently by two other groups. To our knowledge, no previous measurements of comparable precision exist for Mg  I  2853 Å and Mg  II  2803 Å.     

NATURE OF PRECIPITATION AND ACTIVITY OF CUMULUS CONVECTION DURING THE 1991 MEIYU SEASON OF CHANGJIANG-HUAIHE RIVER BASIN*

Seasonal variability regarding the nature of precipitation and the activity of cumulus convection during the 1991 Meiyu season of Changjiang-Huaihe River Basin(Jianghuai)has been investigated by calculating apparent heat source/apparent moisture sink and analyzing TBB(cloud-top blackody radiation temperature)data.It is found that three periods of strong ascending motion during the Meiyu season lead to three episodes of heavy rain,and the latent heat due to the precipitation is of the sole heat source of the atmosphere.The nature of precipitation shows distinct seasonal variability,from frontal precipitation of the first episode to the extremely strong convective precipitation of the third episode.TBB field of East Asia may well reflect not only the intensity of convection and rainfall,but also the movement of rain belt and convection belt.In the whole Meiyu season.convection belt mainly stays in Jianghuai.but may shift within the domain of East Asia.Its locating in Jianghuai or not determines the maintenance or break of Meiyu.In the third episode,the narrow convection belt over Jianghuai is mainly caused by southwest monsoon which takes moist and convective atmosphere from tropical ocean.