Bivalve population health: Multistress to identify hot spots

This study investigated some stress (metals, parasites) and response (immunity, metallothionein) factors in two cockle and two Manila clam populations. Data from eight seasons were averaged to obtain global baseline values. Stress/response characteristics of each population were compared to population health status that was determined through population dynamics parameters. Four different scenarios were discussed: (1) a lightly stressed cockle population with correct population health but with a risk of deterioration (hot spot); (2) a lightly stressed introduced cockle population threatened of extinction. In this case ecological factors were suspected; (3) a moderately stressed clam population with moderate adaptative response. The population was sustainable but the level of stress should not increase (hotspot); and (4) a stressed clam population and unfavourable ecological conditions preventing clam settlement. This monitoring highlighted that the discrepancy between population health and stress levels could be due to insufficient response by bivalves and/or by unfavourable ecological factors.     

New radiometric and petrological constraints on the evolution of the Pichincha volcanic complex (Ecuador)

Fieldwork, radiometric (⁴⁰Ar/³⁹Ar and ¹⁴C) ages and whole-rock geochemistry allow a reconstruction of eruptive stages at the active, mainly dacitic, Pichincha Volcanic Complex (PVC), whose eruptions have repeatedly threatened Quito, most recently from 1999 to 2001. After the emplacement of basal lavas dated at ∼1100 to 900 ka, the eruptive activity of the old Rucu Pichincha volcano lasted from ∼850 ka to ∼150 ka before present (BP) and resulted in a 15 × 20 km-wide edifice, which comprises three main building stages: (1) A lower stratocone (Lower Rucu, ∼160 km³ in volume) developed from ∼850 to 600 ka; (2) This edifice was capped by a steeper-sided and less voluminous cone (the Upper Rucu, 40–50 km³), the history of which started 450–430 ka ago and ended around 250 ka with a sector collapse; (3) A smaller (8–10 km³) but more explosive edifice grew in the avalanche amphitheatre and ended Rucu Pichincha's history about 150 ka ago. The Guagua Pichincha volcano (GGP) was developed from 60 ka on the western flank of Rucu with four growth stages separated by major catastrophic events. (1) From ∼60 to 47 ka, a basal effusive stratocone developed, terminating with a large ash-and-pumice flow event. (2) This basal volcano was followed by a long-lasting dome building stage and related explosive episodes, the latter occurring between 28–30 and 22–23 ka. These first two stages formed the main GGP (∼30 km³), a large part of which was removed by a major collapse 11 ka BP. (3) Sustained explosive activity and viscous lava extrusions gave rise to a new edifice, Toaza (4–5 km³ in volume), which in turn collapsed around 4 ka BP. (4) The ensuing amphitheatre was partly filled by the ∼1-km³ Cristal dome, which is the historically active centre of the Pichincha complex. The average output rate for the whole PVC is 0.29 km³/ka. Nevertheless, the chronostratigraphic resolution we obtained for Lower Rucu Pichincha and for the two main edifices of Guagua Pichincha (main GGP and Toaza), leads to eruptive rates of 0.60–0.65 km³/ka during these construction stages. These output rates are compared to those of other mainly dacitic volcanoes from continental arcs. Our study also supports an overall SiO₂ and large-ion lithophile elements enrichment as the PVC develops. In particular, distinctive geochemical signatures indicate the involvement of a new magma batch at the transition between Rucu and Guagua. At the GGP, the same phenomenon occurs at each major collapse event marking the onset of the ensuing magmatic stage. Since the 11-ka-BP collapse event, this magmatic behaviour has led to increasingly explosive activity. Four explosive cycles of between 100 and 200 years long have taken place at the Cristal dome in the past 3.7 ka, and repose intervals between these cycles have tended to decrease with time. As a consequence, we suggest that the 1999–2001 eruptive period may have initiated a new eruptive cycle that might pose a future hazard to Quito (∼2 million inhabitants).     

Spatial and Temporal Dependence of Temperature Variations Induced by Atmospheric Pressure Variations in Shallow Underground Cavities

Pressure-induced temperature (PIT) variations are systematically observed in the atmosphere of underground cavities. Such PIT variations are due to the compressibility of the air, damped by heat exchange with the rock surface. It is important to characterize such processes for numerous applications, such as the preservation of painted caves or the assessment of the long-term stability of underground laboratories and underground waste repositories. In this paper we thoroughly study the spatiotemporal dependence of the PIT response versus frequency using vertical and horizontal profiles of temperature installed in an abandoned underground quarry located in Vincennes, near Paris. The PIT response varies from about 20 × 10^?3°C hPa^?1 at a frequency of 2 × 10^?4 Hz to 2–3 × 10^?3°C hPa^?1 at a frequency of one cycle per day. An analytical expression based on a simple heat exchange model accounts for the observed features of the PIT response and allows for correcting the measured time series, having standard deviations of about 10^?2°C, to residual variations with a standard deviation of about 2 × 10^?3°C. However, a frequency-dependent attenuation of the response, corresponding to a reduction in amplitude with a factor varying from 2 to 3, is observed near the walls. This effect is not included in the simple analytical expression, but it can be accounted for by a one-dimensional differential equation, solved numerically, where temperature variations in the atmosphere are damped by an effective radiative coupling with the rock surface, complemented by a diffusive coupling near the walls. The TIP response is observed to remain stable over several years, but a large transient enhancement of about a factor of two is observed near the roof at one location from July to October 2005. In a cavity located below the Paris Observatory, an additional contribution is identified in the PIT response function versus frequency for frequencies smaller than 2 × 10^?5 Hz. This contribution can be described using a modified analytical expression that includes the effect of heat diffusion into the surrounding rock. Using this expression, in this case also, the temperature time series can then be corrected, giving a residual standard deviation smaller than 1.6 × 10^?3°C. Transient temporal variations of the PIT response are observed in all sites, with possible nonlinear components in the PIT. Such effects are not properly understood at this stage, and limit the reduction of time series to standard deviations of the order of 2 × 10^?3°C, and consequently limit the search for new transient or seasonal temperature signals, for example due to the presence of tiny heat sources in the cavity or to geodynamical effects.     

复合地基桩体对垫层的刺入量研究

作为研究复合地基荷载传递规律和沉降的一个重要组成部分,桩体刺入变形量的分析与研究将进一步完善复合地基沉降理论,但目前对于桩体刺入量的研究并不多。对现有桩体向垫层刺入量计算方法进行了分析,指出不足之处,提出了更为合理的刺入量计算方法。通过与现有计算方法的比较,表明了方法的合理性。与模型试验结果进行了比较,证明了其方法的适用性。     

Cristobalite in the 2011–2012 Cordón Caulle eruption (Chile)

Cristobalite is a low-pressure high-temperature polymorph of SiO₂ found in many volcanic rocks. Its volcanogenic formation has received attention because (1) pure particulate cristobalite can be toxic when inhaled, and its dispersal in volcanic ash is therefore a potential hazard; and (2) its nominal stability field is at temperatures higher than those of magmatic systems, making it an interesting example of metastable crystallization. We present analyses (by XRD, SEM, EPMA, Laser Raman, and synchrotron μ-cT) of representative rhyolitic pyroclasts and of samples from different facies of the compound lava flow from the 2011–2012 eruption of Cordón Caulle (Chile). Cristobalite was not detected in pyroclasts, negating any concern for respiratory hazards, but it makes up 0–23 wt% of lava samples, occurring as prismatic vapour-deposited crystals in vesicles and/or as a groundmass phase in microcrystalline samples. Textures of lava collected near the vent, which best represent those generated in the conduit, indicate that pore isolation promotes vapour deposition of cristobalite. Mass balance shows that the SiO₂ deposited in isolated pore space can have originated from corrosion of the adjacent groundmass. Textures of lava collected down-flow were modified during transport in the insulated interior of the flow, where protracted cooling, additional vesiculation events, and shearing overprint original textures. In the most slowly cooled and intensely sheared samples from the core of the flow, nearly all original pore space is lost, and vapour-deposited cristobalite crystals are crushed and incorporated into the groundmass as the vesicles in which they formed collapse by strain and compaction of the surrounding matrix. Holocrystalline lava from the core of the flow achieves high mass concentrations of cristobalite as slow cooling allows extensive microlite crystallization and devitrification to form groundmass cristobalite. Vapour deposition and devitrification act concurrently but semi-independently. Both are promoted by slow cooling, and it is ultimately devitrification that most strongly contributes to total cristobalite content in a given flow facies. Our findings provide a new field context in which to address questions that have arisen from the study of cristobalite in dome eruptions, with insight afforded by the fundamentally different emplacement geometries of flows and domes.     

背景场项目中iDirect卫星通信系统设计

介绍背景场项目中i Direct卫星通信系统,主要从背景场项目对卫星通信的需求、系统设计、数据接入、系统应用等方面进行阐述,具体介绍卫星信系统为行业网备份的数据接入方案以及数据应用案例,可独立为国家测震台提供数据传输信道,保障测震速报业务的正常开展。     

基于支持向量机的Q_3黄土孔隙微观结构研究

为了解决利用黄土SEM图像提取孔隙参数的问题,将孔隙区域的提取问题转化为孔隙像素点的分类问题,通过把整个图像的像素点分为孔隙点和骨架点,从而实现孔隙的提取。利用这种方法,对潼关Q3黄土震陷试验前后的微结构图像进行处理,得到了动力作用前后的孔隙分布图,并计算了孔隙面积、面孔隙度、孔隙分形维数等参数,结果表明:震陷试验后大孔隙数量减小,中、小孔隙数量有所增加,震陷主要是由大孔隙破坏所致。     

Globalising New Zealand : Fonterra Co-operative Group, and shaping the future

New Zealanders have little collective vision of their position and future in a globalising world. Recent developments in New Zealand's primary sector show potential pathways to the future. We explore two claims: thinking about New Zealand is to think about the emergence of Fonterra Co-operative Group in New Zealand's globalising economy. Thinking about Fonterra is to think about New Zealand and the implications that spring from globalising activities. Fonterra is a lens to understand better the possibilities and development options and the challenges that are arising as New Zealand forges its place in a globalising world.     

地震导致河流改道与古蜀文明的变迁

对三星堆文明的突然消亡,至今没有令人信服的解释,而岷江支流雁门沟,沱江支流湔江及其上游支流白水河的特殊河流地貌,尚未引起人们的重视.实地考察雁门沟、白水河及湔江,通过其河流地貌特征推断白水河和湔江为断头河,雁门沟为反向河;再利用3S技术,找到了光光山一带大规模滑坡遗迹,从而判定岷江曾在今汶川雁门向东南流,穿越光光山,沿今白水河、湔江流向沱江.岷江及其支流杂谷脑河、雁门沟、文政沟的纵剖面特征,也反映出河流曾发生过大的变迁.结合三星堆、金沙遗址考古资料以及历史文献的进一步论证,最终得出发生于1099 B.C.的地震引起山崩、滑坡堵江,进而引起河流改道,并导致三星堆文明的消亡和金沙文明的传承,以及杜宇时代的严重水灾.     

上海市实物地质资料信息管理与服务系统建设

实物地质资料与原始地质资料、成果地质资料并列为三大地质资料.长期以来,地质资料馆以各种账本来记录某种实物地质资料数量有多少、从何处采集、由谁送采、是谁施工等信息.这些账本交流范围十分有限,从而影响了实物地质资料的利用率.为了解决这一难题,上海市地质调查研究院结合地理信息系统、数据库与网络技术开展实物地质资料信息管理与服务系统建设,来提高实物地质资料的信息化管理水平,更好地服务于社会.