Effects of freeze-thaw cycle and dry-wet alternation on slope stability

The typical loess on high slopes along the BaoLan High-speed Rail, China, was selected as the research object. The influence of the freeze-thaw cycle and dry-wet alternation on the shear-strength parameters of the unsaturated loess was investigated by laboratory experimental methods. Moreover, the temperature field, seepage field, and stability of slopes with different gradients were simulated under the effect of the freeze-thaw cycle and dry-wet alternation by using the geotechnical analysis software Geo-Studio. The research results showed(1) when the freeze-thaw cycle was repeated on the slope, with the frozen depth increasing, the melted depth did the same; besides, the closed loop of isotherms formed on the slope;(2) under the action of dry-wet circulation, the negative pore-water pressure and volumetric water content showed an upward tendency. However, owing to the different slope gradients, rainfall infiltration was not the same. As time went by, the differences of the negative pore-water pressure and volumetric water content between the slopes of different gradients continued to increase;(3) with the freeze-thaw cycle and dry-wet alternation increasing, the slope-safety factor decreased. Especially in the early period, the slope-safety factor changed remarkably. For slopes undergoing freeze-thaw action, the slope-safety factor was negatively correlated with the gradient. However, with regard to slopes undergoing dry-wet alternation, the result became more complex because the slope-safety factor was related to both seepage strength and slope grade. Accordingly, further research is needed to study the effect of seepage strength and slope grade on the stability of loess slopes.     

Seasonal and interannual variability of carbon cycle in South China Sea: A three-dimensional physical-biogeochemical modeling study

The South China Sea (SCS) exhibits strong variations on seasonal to interannual time scale, and the changing Southeast Asian Monsoon has direct impacts on the nutrients and phytoplankton dynamics, as well as the carbon cycle. A Pacific basin-wide physical-biogeochemical model has been developed and used to investigate the physical variations, ecosystem responses, and carbon cycle consequences. The Pacific basin-wide circulation model, based on the Regional Ocean Model Systems (ROMS) with a 50-km spatial resolution, is driven with daily air-sea fluxes derived from the National Centers for Environmental Prediction (NCEP) reanalysis between 1990 and 2004. The biogeochemical processes are simulated with the Carbon, Si(OH)₄, Nitrogen Ecosystem (CoSINE) model consisting of multiple nutrients and plankton functional groups and detailed carbon cycle dynamics. The ROMS-CoSINE model is capable of reproducing many observed features and their variability over the same period at the SouthEast Asian Time-series Study (SEATS) station in the SCS. The integrated air-sea CO₂ flux over the entire SCS reveals a strong seasonal cycle, serving as a source of CO₂ to the atmosphere in spring, summer and autumn, but acting as a sink of CO₂ for the atmosphere in winter. The annual mean sea-to-air CO₂ flux averaged over the entire SCS is +0.33 moles CO₂ m⁻²year⁻¹, which indicates that the SCS is a weak source of CO₂ to the atmosphere. Temperature has a stronger influence on the seasonal variation of pCO₂ than biological activity, and is thus the dominant factor controlling the oceanic pCO₂ in the SCS. The water temperature, seasonal upwelling and Kuroshio intrusion determine the pCO₂ differences at coast of Vietnam and the northwestern region of the Luzon Island. The inverse relationship between the interannual variability of Chl-a in summer near the coast of Vietnam and NINO₃ SST (Sea Surface Temperature) index in January implies that the carbon cycle and primary productivity in the SCS is teleconnected to the Pacific-East Asian large-scale climatic variability.     

圆尾斗鱼的胚胎和仔鱼发育的研究

圆尾斗鱼的受精卵呈圆球形，光滑，略带淡黄色，浮性；卵膜吸水膨胀后的平均直径为１．１９ｍｍ，当水温２１－２３．５℃时，从受精卵到孵化出膜需４２．５小时；水温２２－２４．５℃时，刚出膜仔鱼到卵黄囊消失需４天，到油球消失约２５天。出膜３０天仔鱼的形态基本与成体相似。     

Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay

The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEP_micro) and colorimetric (TEP_color) methods, showed abundant (6.1×10⁶–4.4×10⁷ L^?1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEP_micro and similar vertical profiles of TEP_color. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L^?1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.     

Flow around sunspots from it p-mode frequency shift measurements

We use five-day helioseimic data from the Taiwan Oscillation Network to study the flow around a sunspot, NOAA 7887. The p-mode oscillations in an annular region centered at the sunspot are decomposed into the modes propagating toward and away from the sunspot. We find that the frequency of an outgoing mode is greater than that of the corresponding incoming mode. This indicates that the plasma is flowing outward from the sunspot. The outflow velocity is estimated to be about 40–80 m s^-1.     

The Effect of Helicity Dissipation on the Critical State of an Avalanche Model for Solar Flares

We perform numerical simulations using an avalanche model for solar flares, in which the effect of avalanche event duration is included and the lateral boundary condition can be either open or periodic. The results from the simulations show that self-organized criticality (SOC) exists under a variety of conditions of helicity dissipation, and they are similar in the sense that the indices of power-law distributions of avalanche sizes are the same, while the duration and waiting time distributions differ little. Of interest are: (1) if there exists helicity dissipation in the course of avalanches, SOC exists only when the amount of helicity dissipation per avalanche is small; (2) sudden reductions in the total helicity of the system do not severely disturb SOC, if the amount reduced is moderate; (3) the distribution of waiting times is shown to be exponential, in consistent with the Poisson statistics other avalanche models have predicted, and the exponent increases as the effect of event duration becomes larger. The self-similar structure of the avalanche time series is also examined. These results imply that, although helicity is dissipated in resistive diffusion of flares, the amount of dissipation should be small and the conservation law of helicity thus holds in an approximate sense. Also, the coronal mass ejections (CMEs), observed to take helicity out of the solar corona in an eruptive way, may disrupt the statistical equilibrium of the corona only temporarily.     

煤矿区水文地质勘查现状及建议

20世纪末以前,我国煤田地质勘察遵循水文地质工作先行的原则,为保障煤矿区开发建设做出了积极的贡献.进入新世纪以来,随着我国国民经济的快速发展,对能源的需求大幅增长,但煤田水文地质工作没引起足够的重视.煤矿区干旱缺水、突水水害严重、环境问题凸显,而煤田水文地质工作严重滞后于煤炭工业可持续发展的需要.建议把煤田水文地质工作作为基础性、战略性地质工作,纳入国家"3性"地质工作(基础性、公益性地质工作及战略性矿产勘查工作),予以重视加强,以保障我国煤炭工业持续稳定健康的发展.     

Fate of paralytic shellfish poisoning toxins in purple clam Hiatula rostrata,in outdoor culture and laboratory culture

Purple clams (Hiatula rostrata Lighttoot) accumulate paralytic shellfish poisoning (PSP) toxins produced by a toxic strain of the dinoflagellate Alexandriun minutum Halim. The results confirm the data of our previous study concerning the muscle and siphon that were not showing a gradual rise in toxicity when shellfish accumulated more A. minutum. However, muscle and siphon are intermittently toxic both in exposure and depuration period in laboratory cultured purple clams. PSP toxins were detected in outdoor cultured purple clams, whereas no A. minutum were found in the culture pond during most of the survey time. The outdoor cultured purple clams need longer time to decrease toxicity to allowable levels than laboratory cultured purple clams. It was shown that laboratory data may not predict times over which pond-cultured purple clams may prove toxic to consumers.     

The carbonate system in the East China Sea in winter

Measurements of dissolved inorganic carbon (DIC), pH, total alkalinity (TA), and partial pressure of CO₂ (pCO₂) were conducted at a total of 25 stations along four cross shelf transects in the East China Sea (ECS) in January 2008. Results showed that their distributions in the surface water corresponded well to the general circulation pattern in the ECS. Low DIC and pCO₂ and high pH were found in the warm and saline Kuroshio Current water flowing northeastward along the shelf break, whereas high DIC and pCO₂ and low pH were mainly observed in the cold and less saline China Coastal Current water flowing southward along the coast of Mainland China. Difference between surface water and atmospheric pCO₂ (ΔpCO₂), ranging from ~ 0 to ? 111 μatm, indicated that the entire ECS shelf acted as a CO₂ sink during winter with an average flux of CO₂ of ?13.7 ± 5.7 (mmol C m^? 2 day^? 1), and is consistent with previous studies. However, pCO₂ was negatively correlated with temperature for surface waters lower than 20 °C, in contrast to the positive correlation found in the 1990s. Moreover, the wintertime ΔpCO₂ in the inner shelf near the Changjiang River estuary has appreciably decreased since the early 1990s, suggesting a decline of CO₂ sequestration capacity in this region. However, the actual causes for the observed relationship between these decadal changes and the increased eutrophication over recent decades are worth further study.     

Luminescence dating of Late Pleistocene faults as evidence of uplift and active tectonics in Sardinia,W Mediterranean

Precise dating of the activity of Late Pleistocene to Holocene neo‐tectonic structures is crucial to quantify the rate of deformation in low‐seismicity regions. Sardinia is a relatively stable continental fragment set in the middle of the tectonically active Western Mediterranean belt. This paper provides evidences of significant uplift of northwest Sardinia that support an ongoing tectonic activity since the Marine Isotopic Stage 7 (MIS 7; ca. 220 ka). In particular, it documents for the first time Late Pleistocene to Holocene tectonics based on luminescence dating of travertine sealing a major NNE‐SSW fault.