Periodical light variations of t tauri stars as a result of disk accretion

I argue that temperatures of spots, responsible for observed periodical light variations of T Tauri stars (TTS), are not known with reliable accuracy to discriminate between chromospheric and accretion theories of TTS 's phenomenon. The hypothesis is set up that spots on classical TTS (CTTS) are due to heating of stellar surface by radiation from a collisional accretion shock, whereas spots on weak line TTS (WTTS), at least in some cases, are connected with a collisionless accretion shock rather than chromospheric activity. Possible scenarios of WTTS interaction with circumstellar matter are discussed.     

Tephrochronology and tephrostratigraphy of two Pleistocene continental fossiliferous successions from central Italy

The stratigraphical context of two Middle Pleistocene fossiliferous palaeosols from Central Italy (Abruzzo and Tuscany) have been studied. Small mammals and molluscs occur in both palaeosols, which are covered by tephra layers that were analysed using an interdisciplinary approach. Application of fission‐track dating to apatites separated from the Case Picconetto tephra (Pescara, Abruzzo), yielded an age of 0.48 ± 0.04 Ma, indistinguishable from those previously determined for the Campani Quarry (Lower Valdarno, Tuscany) (0.46 ± 0.05 Ma and 0.48 ± 0.05 Ma). Geochemical and petrographic investigations indicate that these tephra originated from different volcanoes, the Alban Hills Volcanic Complex and the Vico Volcano (Latium) respectively. Small mammal and mollusc assemblages indicate different palaeoclimatic and palaeoenvironmental conditions for the Case Picconetto and Campani Quarry palaeosols. Warm and humid conditions can be inferred for the Campani Quarry site, whereas open and cold conditions can be inferred for Case Picconetto. On the basis of faunal data, fission‐track dates and attribution of tephra to specific volcanic eruptions, we suggest a correlation of these faunas with marine oxygen isotope stage 14 (Case Picconetto) and with marine oxygen isotope stage 11 (Campani Quarry), respectively. Copyright © 2003 John Wiley & Sons, Ltd.     

Mezen Bay—a key area for understanding Weichselian glaciations in northern Russia

Sediment successions in coastal cliffs around Mezen Bay, southeastern White Sea, record an unusually detailed history of former glaciations, interstadial marine and fluvial events from the Weichselian. A regional glaciation model for the Weichselian is based on new data from the Mezen Bay area and previously published data from adjacent areas. Following the Mikulinian (Eemian) interglacial a shelf‐centred glaciation in the Kara Sea is reflected in proglacial conditions at 100–90 ka. A local ice‐cap over the Timan ridge existed between 75 and 65 ka. Renewed glaciation in the Kara Sea spread southwestwards around 60 ka only, interrupted by a marine inundation, before it advanced to its maximum position at about 55–50 ka. After a prolonged ice‐free period, the Scandinavian ice‐sheet invaded the area from the west and terminated east of Mezen Bay about 17 ka. The previously published evidence of a large ice‐dammed lake in the central Arkhangelsk region, Lake Komi, finds no support in this study. Copyright © 2003 John Wiley & Sons, Ltd.     

Sedimentary characteristics of tide-dominated estuary in Donghetang Formation（Upper Devonian）, central Tarim Basin

The Donghetang Formation （Upper Devonian） in central Tarim Basin has been thought an important oil and gas reservoir since the abundant oil and gas resources were found in the wells W16, W20, W34, and other fields. However, the sedimentary environment of the Donghetang Formation has been disputed because it suffered from both tidal and fluvial actions and there were not rich fossils in the sandstone. After the authors analyzed sedimentary features by means of drill cores, well logging data, paleosols, and with SEM obseruations, three kinds of sedimentary environments were distinguished： alluvial fan, tide-dominated estuary, and shelf. Particularly, the sedimentary features of tide-dominated estuary were studied in detail. Besides, the authors discussed sedimentary characteristics of the Donghetang Formation which was divided into two fourth-order sequences and five system tracts. At the same time, according to the forming process of five system tracts, the whole vertical evolution and lateral transition of tide-dominated estuary were illustrated clearly. Finally, the reservoir quality was evaluated based on porosity and permeability.     

Palaeotemperature reconstructions of the European permafrost zone during marine oxygen isotope Stage 3 compared with climate model results

A palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd.     

一种新的温度记录器

本文提出一个以带有定时器的低功耗微处理机为主体的温度记录器。其定时器用于开动微处理机,可由一个开关定为0.5、1、3或30分钟。仪器通过处理一个电容器向热敏电阻放电的时间来测量温度。仪器在工作中能显示温度值,并把温度值保存在微处理机的RAM之中。总共资料容量为2816次测值,量程为0～35℃,精度±0.1℃,分辨±0.02℃。 温度记录器具有液晶显示器,可直接读出温度值,配有标准计算机接口RS-232,能把保存的资料方便地倒给个人计算机。 这项工作是伍兹霍尔海洋研究所A.Bradley博士指导的。他提出的原理对研制可靠而廉价的温度记录器是一条新的途径。     

Spatial patterns and environmental risks of ringnet fishing along the Kenyan coast

Ringnet fishing began in the early 20th century and is practised worldwide, mainly to target nearshore pelagic species. The method was introduced to Kenya’s coastal waters by migrant fishers from Tanzania. However, the impacts of this fishing gear remain poorly assessed. We assessed the spatial distribution of ringnet fishing effort and its possible effects on ecosystem components, such as coral reefs, marine megafauna and marine protected areas, on the south coast of Kenya. We tracked 89 ringnet fishing trips made from December 2015 to January 2016 and used spatial multicriteria analysis to determine hotspots of possible environmental risks. The results showed that habitat type and bathymetric profile influenced the spatial distribution of ringnet fishing effort. Mixed seagrass and coral habitats had the highest concentration of the effort. Most of the habitats in the study area were moderately exposed to the impacts of the ringnet fishery. The study identifies high-risk areas that require spatial measures to minimise possible environmental risks of the gear both to habitats and to endangered sea turtles.     

Photoinduced toxicity single and binary mixtures of four polycyclic aromatic hydrocarbons to the marine diatom Skeletonema costatum

Diatom Skeletonema costatum Cleve is one of the main predominant phytoplankton species in the Changjiang Estuary in China. In order to provide some basic information for future assessment of the potential risk on phytoplankton communities in this estuary caused by polycyclic aromatic hydrocarbons(PAHs), this alga was selected as a representative to investigate the photoinduced toxicity of PAHs, in single and mixture. Four PAHs including three-ring phenanthrene and anthracene, four-ring fluoranthene and pyrene were tested in the laboratory. The single toxicity of each PAH on this microalga was compared with and without the simulated solar UV radiation. The results showed that this microalga was sensitive to PAH's photoinduced toxicity. Ratios of the 72 h median effect concentration obtained for fluorescent and UV light tests were about 8.4 for phenanthrene, 13.0 for anthracene, 6.5 for fluoranthene, and 5.7 for pyrene, indicating that UV light enhanced the PAH toxicity to this alga significantly. Under the fluorescent radiation (lacking UV), the dose-response curves based on chemical concentrations revealed that the order of toxic strength was fluoranthene greater than pyrene greater than anthracene greater than phenanthrene; while under the UV radiation (476 μW/cm2 for UVA, 6.5 μW/cm2 for UVB) it became fluoranthene approximately equaling anthracene greater than pyrene greater than phenanthrene, indicating that the UV light also changed its relative toxicity to this alga. The photoinduced toxicity of PAHs to the marine diatom S. costatum might be a synergistic effect of photosensitization reactions (e.g., generation of single-state oxygen) and photomodification (photooxidation and/or photolysis).The combined effects of six binary mixtures on the marine diatom S. costatum were investigated using the additive-index method. Four binary-mixtures (phenanthrene plus anthracene; phenanthrene plus pyrene; anthracene plus fluoranthene; anthracene plus pyrene) were found to be synergistic joint action mode, while two binary-mixtures (phenanthrene plus fluoranthene; fluoranthene plus pyrene) displayed antagonist, revealing a complex pattern of possible interactions. The combined action mode of PAHs might be related to various factors such as the mixture compounds, mixture ratios and test conditions, etc.     

大黄鱼倍性检测研究

于2001—2004年对人工诱导大黄鱼的不同发育阶段和不同组织进行倍性检测，胚胎眼泡期采用染色体计数法测定，鱼苗和成鱼阶段用流式细胞法，结果表明，胚胎染色体数目2n=48条为二倍体，3n=72条为三倍体．采用流式细胞法测定鱼苗和成鱼个体时，若受测样品的DNA相对含量值与已知对照组二倍体的比值约为1．5：1，其个体为三倍体；比值约为1：1，则为二倍体，无论用肌肉或尾鳍组织，皆可检测出其个体的倍性。