北秦岭西段冥古宙锆石(4.1～3.9Ga)年代学新进展

2007年王洪亮等报道在北秦岭西段火山岩中获得一粒年龄为4079±5Ma的冥古宙捕虏锆石。之后,对这一发现开展了深入的调查研究,我们除利用SHIMP技术方法对原4079Ma的锆石进行验证外,新获得了两粒~(207)Pb/~(206)Pb年龄为4007±29Ma和3908±45Ma捕获的变质成因锆石,表明早在4.0Ga已经有变质作用的发生,这或许说明在冥古宙时期地球已经具有相当规模和厚度的地壳。同时开展的岩石学研究表明,蕴含古老锆石的母岩属于火山碎屑熔岩类而不是火山熔岩。     

Maar-diatreme phreatomagmatism at Hopi Buttes,Navajo Nation (Arizona), USA

Remnants of an extensive maar-diatreme volcanic field are magnificently exposed at various depths of erosion in the Hopi Buttes volcanic field of northeastern Arizona. Field and petrographic studies of both the maar and diatreme elements of a selection of volcanoes within the field show that: (1) lower sections of the maar rim sequences are typically rich in sandy mudrock derived from the pre-eruptive Mio-Pliocene Bidahochi Formation, and the muddy Bidahochi sediment was soft and wet at the time of maar eruptions; (2) beds higher within the rims contain generally increased proportions of sandstone clasts from the Triassic Wingate Formation. In the diatremes, late-emplaced breccia has deeper-seated lithics than more marginal breccia emplaced earlier; and (3) many vents are topped by megacryst-enriched scoria and spatter, and deep-seated xenoliths are known only from upper diatreme and craterfilling tephra. These observations show that: (1) eruptions at Hopi Buttes involved interaction of magma with unconsolidated mudrock at shallow levels, and the phreatomagmatic processes that provided the bulk of the energy involved in the violent eruptions were driven by the interaction of magma and wet sediment; (2) the locus of explosive activity migrated downward as eruptions progressed; and (3) the closing stage of many eruptions was characterized by rapid magma rise and relative depletion of water.     

Seasonal dynamics and production of the hydromedusan Clytia hemisphaerica (Hydromedusa: Leptomedusa) in Southampton water

In 1990 and 1991, a zooplankton sampling program revealed the presence of the hydromedusan Clytia hemisphaerica (Hydromedusa: Leptomedusa) from early May through late September throughout Southampton Water. The most notable aspects of the population dynamics of C. hemisphaerica in Southampton Water were the considerable interannual variation in peak abundance—10.65 m^?3 in 1990 and 2.44 m^?3 in 1991—and temporal patterns of mean bell diameter. The suggestion of almost continuous reproduction in 1990, as indicated by high abundance and large size range on each sampling date, is in contrast to 1991, where at the Cracknore site, five cohorts were produced at 21 d to 80 d intervals. The maximum bell diameter attained in each generation was typically 10–11 mm. At the Cracknore site in 1991, in situ bell diameter growth was linear within each cohort. A trend of increased growth rate with each subsequent cohort, from 26 μg DW d^?1 to 106 μg DW d^?1 was coincident with increasing water temperature. Annual production ranged from 0.98 mg C m^?3 yr^?1 to 1.08 mg C m^?3 yr^?1 in 1990 and 0.35 mg C m^?3 yr ^?1 to 0.48 mg C m^?3 yr^?1 in 1991. Daily P: B ratios varied in each cohort from 0.05 to 0.35.     

Meiofauna in closed coastal saline lagoons in the United Kingdom: Structure and biodiversity of the nematode assemblage

Coastal saline lagoons are rare in North West Europe and tend to be closed, brackish water systems. In the United Kingdom they are small and isolated, each exhibiting extremely variable habitat conditions, both spatially and temporally. This paper represents the first species-level study of lagoonal nematode assemblages in the UK. Samples were taken from seven ponds in a saline lagoon system on the south coast of England in order to describe the nematode assemblage in relation to habitat type and to assess the possibility of lagoonal specialisation. At each site samples were also taken, or data were already available, for salinity, sediment granulometry, sediment organic carbon content, photosynthetic pigments and lagoon topography.     

The cytochrome P450 1A gene (CYP1A) from European flounder (Platichthys flesus), analysis of regulatory regions and development of a dual luciferase reporter gene system.

Concensus primers designed to CYP1A-conserved regions were used to amplify a 1.3 kb probe from flounder genomic DNA via polymerase chain reaction (PCR). A 14-kb clone was isolated from a flounder genomic library constructed in lambda FIXII. Of this clone, 8 kb was sequenced, including 3 kb of upstream sequence. The predicted amino acid sequence showed closest similarity to plaice CYP1A1 (98%). Gene structure conformed to the seven exons and six introns common to previous CYP1A sequences, but intron lengths were not conserved. Concensus sequences corresponding to xenobiotic and other response elements as well as TATA, CAAT and GC boxes were identified. Upstream sequence (3.5 kb) including the first exon and intron up to the putative start codon were amplified via PCR and inserted upstream of the luciferase gene in a pGL3 reporter gene construct. The HepG2 mammalian hepatoma cell line was transiently co-transfected with the flounder CYP1A reporter gene construct and the pRL-CMV internal control construct. The maximal induction upon exposure to 100 nM 3-MC was 4.4-fold in comparison with carrier-treated cells. Use of deletion constructs resulted in loss of inducibility.     

Isolation of differentially expressed genes from contaminant exposed European flounder by suppressive, subtractive hybridisation

Commercially farmed European flounder (Platichthys flesus) were treated with benzo[a]pyrene or cadmium under controlled laboratory conditions. In addition, animals were collected from the polluted Tyne and relatively clean Alde estuaries in the UK. Potential differentially expressed genes were isolated from liver tissue by means of suppressive, subtractive hybridisation. A total of 284 different mRNAs were identified as having the potential for being differentially expressed, of which 84 could be tentatively identified by homology with database sequences. These clones will form part of a flounder cDNA array for validation and future applications, with full identification being pursued for those expressed sequence tags for which differential expression can be confirmed by array technology.