Construction of two selectable markers for integrative/conjugative plasmids in Flavobacterium columnare

Flavobacterium columnare, the etiological agent of columnaris disease, is one of the most important and widespread bacterial pathogens of freshwater fish. In this study, we constructed two artificial selectable markers (chloramphenicol and spectinomycin resistance) for gene transfer in F. columnare. These two new artificial selectable markers, which were created by placing the chloramphenicol or spectinomycin resistance gene under the control of the native acs regulatory region of F. columnare, were functional in both F. columnare and Escherichia coli. The integrative/conjugative plasmids constructed by using these markers were introduced into F. columnare G4 via electroporation or conjugation. The integrated plasmid DNA was confirmed by Southern blotting and PCR analysis. These two markers can be employed in future investigations into gene deletion and the pathogenicity of virulence factors in F. columnare.     

An infrared study of Be stars based on ISO SWS01 spectra

The Infrared Space Observatory (ISO) Short-Wavelength Spectrometer (SWS) spectra of 10 Be stars are presented. It can be seen that the Be stars show a diversity in their ISO SWS01 spectral classifications by Kraemer et al., from naked stars, stars associated with dust, stars with warm dust shells, stars with cool dust shells to very red sources. In addition, the Brc/HI(14-6) line flux ratio derived for the sample stars is compared with that of P Cyg, and it is found that the line ratio of Be stars which were investigated show not only lower values as suggested by Waters et al., but also larger values. Therefore, the line ratio cannot he used to judge whether a star is a Be star or not.     

Deep-Water Bottom Current Research in the Northern South China Sea

This article discusses an effective way to study deep-water current activity with the sedimentary features of seabed sediments. In the paper, we have processed a seismic survey line crossing the Northwest sub-basin of the South China Sea (SCS). In the seismic profile, we can clearly distinguish the contourite sediment waves and find the erosion scope formed by the deep-water bottom current. Combining the analytic result of piston cores sediments in the research area, we can conclude that the deep-water current is the contour current. It enters the SCS through the narrow Bashi Channel and then it flows to the southwest direction along the isobaths of Dongsha uplift and Southern uplift, but there isn't direct evidence to explain that bottom current flows to the direction of the deep-sea basin. The conclusion confirms former speculation about the passage of deep-water current and provides an important foundation to construct the whole structure of deep-water circulation for the SCS.     

全数字化成图内业测点拟合问题的探讨

就大比例尺数字化内业成图中所遇到的精度范围内的测点点位拟合做了简要探讨。     

Crustal structure from spectral ratio of short-period P waves

This study examines the method of spectral ratio response and verifies a structure beneath Umeå from short-period P waves of teleseismic events. Previously, researchers reported difficulty in interpreting observed ratios of short-period waves in terms of realistic models. Compatible results are returned here by restricting the length of analysis to a short duration (about 12 s) with the understanding that only the gross features of the crust may be modelled. Our results indicate a 42-km two-layer shield structure similar to that derived from long-period P waves. The structure so inferred is attributed to considerations of the observed and theoretical model truncated ratios in the frequency range 0.9–1.3 Hz, the dominant periods of the signals analysed, a short data window, analysis of records with a well-developed beat character and a relatively simple crust beneath the recording station.     

一维反散射层速度反演

利用参考速度进行波动方程的坐标变换和玻恩近似,建立了把散射势与速度扰动项相联系的积分方程,通过求解振动项,获得了层速度与界面的反演结果。文中所用的合成记录反演结果表明了本方法运算速度快、精度高,前提条件少。     

Early Ordovician continental break-up in Variscan Europe: Nd---Sr isotope and trace element evidence from bimodal igneous associations of the Southern Massif Central, France

The high-grade Marvejols Group and the low-grade Albigeois-Cévennes sedimentary sequence contain bimodal igneous rocks of Early Ordovician age which are representative of a widespread thermal event in the European Variscides. Comparison of their Nd---Sr isotope and trace-element characteristics provides additional evidence for their origin in an ensialic extensional setting. As an alternative to the back-arc model proposed by previous authors, we propose that these associations record a continental break-up episode unrelated to contemporaneous subduction. In this model, the widespread Early Paleozoic bimodal magmatism marks the birth of a Mid-European oceanic arm. We propose that the break-up was controlled by both transtensional processes and mantle-plume activity.

High grade associations, such as the Marvejols Group, and low-grade bimodal associations, such as the Albigeois-Cévennes, might be regarded as representing opposite rifted passive margins. The “northern”, Marvejols-type margin was involved in a Late Ordovician-Silurian subduction-like process, with HP-HT metamorphism. In contrast, the “southern” Albigeois/Cévennes margin remained largely unaffected, possibly as part of the overriding plate of the subduction zone.

“Pseudo-calc-alkaline” signatures unrelated to subduction processes may occur in magmatic rocks associated with continental break-up episodes. In this case, negative Nb anomalies are produced by the addition of crustal components enriched in Th and LREE relative to Nb. This inferred alternative origin of Nb anomalies has important bearing on the paleogeodynamic settings based on geochemical data.     

德清序村萤石矿的同位素研究

本文公布序村萤石矿的氢和锶同位素分析结果.讨论了成矿溶液和成矿物质Sr、Ba、Ca的来源,指出成矿溶液中存在有HF和SiF_4.