黑龙江西三江地区早白垩世孢粉组合

本文研究黑龙江东部西三江地区中生代煤系地层3个岩组中的孢粉组合。其中城子河组孢粉组合丰富,时代属欧特里期至巴列姆期,但目前材料尚不能对城子河组进行有意义的孢粉地层再分。穆棱组下部与城子河组的孢粉组合相似,反映植物群的渐变过程。东荣组的孢粉组合及其与邻区地层的对比关系亦有讨论,其时代有属凡兰吟期的可能。     

Qualitative changes in the planktonic Cladocera assemblage of a High Tatra Mountains lake during the last 100 years

During the last roughly 100 years (1881–1989) some noteworthy changes have occurred in the planktonic Cladocera taxocene of the lake Popradské pleso (High Tatra Mts., Czecho-Slovakia). Primarily, in course of the twenties up to the fifties of our century Daphnia pulicaria and Polyphemus pediculus, and later also Holopedium gibberum, disappeared from the plankton of the lake. Conversely, approximately from the mid-seventies, Daphnia longispina has become a constituent of the lake plankton. In spite of lacking data on the principal parameters of the abiotic and biotic environment from the past, the author assumes that probably the most important factor responsible for the changes referred to were fluctuations in the predation pressure of fish. Besides, organic pollution might have played a definite but less important role.     

Comparison of the impacts of consumers, ambient UV, and future UVB irradiance on mid-latitudinal macroepibenthic assemblages

Future levels in ultraviolet-B (UVB) radiation are expected to increase directly due to stratospheric ozone depletion and under water indirectly by, for example, global warming effects on DOC concentrations, altered trophic interactions in the plankton, or reduced eutrophication. While detrimental UV effects have been reported at the cellular level, little to nothing is known about community-wide effects of ambient and future UVB radiation. In a 4-month field experiment, the ambient UV regime was (i) reduced by cut-off filters which removed either UVB or total UV from the solar spectrum or (ii) increased to predicted future levels by UVB lamps. To allow relating the effects of present and future UV regimes to another important ecological control of community structure and diversity in subtidal marine habitats, consumer effects were quantified by an exclusion treatment under ambient light regimes. Ambient UV regimes did not affect community structure, biomass accrual, and diversity. In contrast, under enhanced UVB levels, the dominance of the competitively superior blue mussels increased and species richness and biomass accrual decreased. Species composition of the assemblages differed between the two UV regimes. Effects of enhanced UVB radiation and of consumption on biomass accrual, diversity, and structure of the community were comparable in magnitude and timing, but of opposite direction. In contrast, the effects of enhanced UVB radiation on growth and abundance of mussels were in the same direction, but shorter and weaker than consumer effects. Most UV effects were transitory and vanished within the first 2 months of succession. Our results indicate that present and future UVB levels may be of limited importance and not stronger in effect size than other ecological controls in structuring the shallow-water low-diversity macrobenthic communities in temperate regions.     

Spatial and temporal variability in early successional patterns of an invertebrate assemblage at an offshore oil platform

The effects of selected physical and biological factors on the early development of a subtidal invertebrate assemblage were examined at an offshore oil platform in the Santa Barbara Channel (California, USA). The effects of date, year, length, and depth of submersion were investigated by replacing sets of ceramic tiles with new tiles at frequencies of 2, 4, 6, 12, and 24 months at three depths (6, 12, and 18 m) over a period of 24 months. The effects of existing colonists and depth were explored in a second experiment by removing selected early colonists from ceramic tiles deployed at the same three depths over a period of 12 months. More than 40 invertebrate taxa from seven phyla colonized the tiles. Colonial tunicates and encrusting bryozoans appeared early in the successional sequence (∼2 months), in cover ranging from <5% to 80% and from <5% to 55%, respectively. Tubiculous amphipods, barnacles, and sponges could also appear early, but in low cover (<20%). Composition of the assemblage changed over time with barnacles, sponges, and mussels becoming the principal space holders on tiles submerged for 24 months. When potential competitors were removed monthly, variation in the cover of dominant taxa (i.e., bryozoans, amphipods, barnacles) was maintained to 12 months, suggesting that other factors, such as larval availability or post-settlement mortality, were responsible for these patterns. Development of this assemblage appeared to fit a pattern of early succession that was largely predictable in terms of the composition and sequence of occurrence of dominant taxa, but variable in rate of development, depending on date of submersion, year, and depth.     

Telomere Shortening in Human HL60 Cells by Treatment with 3′-Azido-2′,3′-Dideoxynucleosides and Telomerase Inhibition by Their 5′-Triphosphates

Telomerase is thought to play an important role in the mechanism of tumor cell immortalization by maintenance of telomere length. To obtain information on the susceptibility of telomerase to nucleoside analogues, the effects of base-modified 3′-azido-2′,3′-dideoxynucleoside triphosphates on the enzyme were investigated. It is suggested that the 2-amino group of the nucleotide purine nucleus is important for the inhibitory activity. Telomere shortening caused by long-term treatment with these nucleosides is also described.     

The Vallonnet cave on the northern Mediterranean border: A record of one of the oldest human presences in Europe

Prehistoric sites testifying to human presence older than one million years in Europe are rare, and in the current state of knowledge, the oldest of them have been dated to around 1.4–1.5 Ma. The Vallonnet cave at Roquebrune-Cap-Martin in the Alpes-Maritimes, on the Mediterranean border, is one of the oldest sites in France to have yielded evidence of human activity: a lithic assemblage of about a hundred pieces and traces of butchery on bones of an Epivillafranchian fauna. The archaeological levels of this small cave were recently dated between 1.1 and 1.2 Ma by U-Pb correlated with paleomagnetic data. The site was occupied alternately by large carnivores that used it as a den or a lair, and by hominins that stayed there briefly in bivouac. The lithic remains are mainly percussion tools, shaped pebbles, flakes and cores, whose raw materials are local, or even semi-local, and on the whole not very diversified with mainly limestone, and to a lesser extent sandstone, quartzite, flint and quartz. This assemblage is attributed to a Mode 1 technology (Oldowayen), among which macro-tools (hammerstones, shaped and fractured pebbles) are found alongside rarer elements resulting from debitage operating chains aimed at producing sharp-edged flakes, very rarely retouched. The bipolar-on-anvil flaking technique could be identified from the characteristics of some artifacts. Several refitting flakes on shaped pebbles or percussion tools attest to knapping and percussion activities in the cave. Hominins consumed the remains of large herbivore carcasses, as attested by the presence of cutting and fracturing marks on some bones. The presence of a freshwater source in the immediate vicinity, and the knapping and butchering activities here therefore document the subsistence behavior of Lower Pleistocene human groups, certainly in competition with the carnivores present.     

宁夏青铜峡鸽子山第15地点发掘报告

宁夏鸽子山遗址位于贺兰山西南余脉东侧的山前洪冲积扇前缘。2015年对第15地点的发掘面积约16m²。在约3m深的地层中共揭露3个原生文化层位。光释光测年数据显示第2层至第4层的时代跨度为0.12-12.3 ka,出土石制品共155件。其中第3层石制品最为丰富,共142件,石制品原料以石英岩和灰岩为主,类型主要有石片、石核和断块。石制品的基本信息显示该地区人类活动频度可能与环境变化与沙漠进退有紧密联系。