Long-Term Changes in Population Dynamics of the Shrimp Palaemon longirostris in the Gironde Estuary

Spanning 20?years (1979?C2007), this study is the longest time series pertaining to the resident shrimp species Palaemon longirostris in a European estuary. Data from monthly faunal surveys undertaken across the middle part of the Gironde estuary from April 1979 along with data from a statistical analysis of the commercial catches throughout the entire estuary and river were considered in order to explore their inter and intra-annual variability and long-term trends. Long-term densities series as well as environmental series (salinity, discharge, temperature and NAO) were decomposed and the effects of environmental variables were also examined using statistical models (GAMs). This revealed important spatio-temporal variability and a significant overall decrease in abundance of this species in the Gironde estuary since the beginning of the 1980s. This long-term decrease in abundance corresponded significantly to long-term decreases in both discharge and the NAO index, as well a long-term increase in temperature and salinity in the middle part of the estuary. However, models showed that environmental factors explained only a small part of the variability. The upstream shift of the population highlighted in this study, probably due to the intrusion of marine waters into the middle section of the estuary, may also have contributed to its decrease in abundance. Inter-annual variability of densities was also significantly linked with inter-annual fecundity fluctuations, and a significant decrease in both mean female size and fecundity was shown for preserved samples from 1992. Moreover, the breeding period has been temporally stretched out and began earlier in more recent years, potentially due to the increase in spring temperature.     

Seismic evidence of up to 200 m lake‐level change in Southern Patagonia since Marine Isotope Stage 4

Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south‐eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80 m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo‐shorelines indicating a stepwise water‐level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake‐level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33 m below present‐day lake level point towards a long period of lake‐level highstand between roughly 53·5 ka cal. bp and 30 ka cal. bp with a maximum lake level some 200 m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30 ka cal. bp and 6750 yrs cal. bp . Dryer conditions during the Mid‐Holocene are evidenced by a dropping lake level, resulting in a basin‐wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5·8 to 5·4 ka cal. bp and ca 4·7 to 4 ka cal. bp with palaeo‐shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions.     

Potential Field,Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District,Northern Sweden

Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum ～ 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (～ 1.5 km) and (ii) deep (～4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data.     

基于在线示踪技术的岩溶地下河流场反演与水文地质参数估算

以青木关岩溶地下河为例,利用在线高分辨率示踪技术获取基础数据来探寻岩溶地下河形态特征,估算水文地质参数。试验中示踪剂回收率高达99 %,示踪剂历时浓度曲线有两个孤峰,前后峰值浓度分别为37.63 μg/L和1.21 μg/L, 两个孤峰的偏度和峰度均大于0,据此推测青木关岩溶地下河并无较大溶潭发育,且地下河流态为紊流流态。根据试验所得数据结合地下河地理空间信息,以经验公式估算得到地下河平均流速、摩擦系数、雷诺数、舍伍德数、施密特数等水文地质参数,分别为204 m/d、0.26、127 980、4 165、1 140,表明青木关地下河管道内部结构复杂,地下水环境比较脆弱,且估算得到的雷诺数所表征的地下河水流态与示踪剂历时浓度曲线得到的结果一致。      

Progress in the determination of Ac in sea water

²²⁷Ac is a naturally occurring radioisotope with a unique combination of properties that make it suitable for the determination of deep ocean mixing and upwelling rates. Here, we present a method for the determination of ²²⁷Ac in sea water on sample sizes of 20–80 L. The measurement is based on co-precipitation of ²²⁷ Ac with MnO₂, followed by chemical isolation of actinium in the presence of an artificial Ac isotope. Actinium is then electrodeposited onto silver discs. In two alpha-spectrometric counting periods, first the artificial ²²⁵Ac isotope is counted, then after > 100 days five daughters of ²²⁷Ac. The first counting period gives a total yield for the procedure, integrating chemical recovery and detector efficiency. The total yield was found here to be on average 15 ± 5%, the chemical yield on average about 50%. The counting of five decay products of ²²⁷Ac in the second period makes the method particularly sensitive. Using appropriate decay corrections, the initial ²²⁷Ac activity can be determined to better than 10% relative error for concentrations < 10,000 atoms/L. We compare data acquired by the new method to a data set from in-situ pumps, from a parallel sampling campaign in the Eastern Weddell Gyre, and we can show excellent agreement. Repeated determinations of ²²⁷Ac in a uranium reference material (UREM-11) demonstrate the accuracy of the method.     

越南河内市冬作物生长季降水量ARIMA预测模型

考虑了气候系统中一些变量突变时可能对预测关系的改变作用，用ARIMA（Auto-Regressive Integrated Moving Average)动态模型的建摸方法，通过SAS软件的计算，建立河内冬作物生长季降水量预测模型。用1996－1998年的独立资料检验，预测结果与实况接近。     

矿物热分解动力学的研究方法探讨

:矿物分解动力学的研究可以大大提高我们对地质作用过程中矿物生长、元素和流体迁移等过程的了解。本文在介绍固相反应动力学原理的基础上 ,讨论了常压下研究矿物分解动力学的热重分析法和电导率法 ,指出精确确定高压下的反应分数 ,是研究高压下矿物热分解动力学的关键。提出了高压下确定反应分数的方法。     

A fluid inclusion and light element stable isotope study of the gold-bearing quartz vein system,Falun, Sweden

The Falun gold quartz vein mineralization is located ca 230 km NW of Stockholm, Sweden, within the Early Proterozoic volcano-sedimentary sequence of Bergslagen. The mineralization consists of a system with subparallel quartz veins that crosscut the alteration zone to the Falun massive sulphide deposit. Early barren and late gold-bearing quartz veins follow tectonic structures postdating the formation of the massive sulphide ore. Both generations of veins are epigenetic to the massive sulphide ore and were formed by hydrothermal processes. Fluid inclusion study of the gold-bearing quartz veins indicates a low-moderately saline fluid (0.3 to 17.4 equiv wt% NaCl). Heterogeneous trapping is indicated by coexisting inclusions showing a variable CO₂ content from 100% CO₂ ± CH₄ to 100% aqueous fluid. Temperatures of total homogenization also show a wide spread from 116–350°C with a slightly bimodal distribution with peaks at ca 180°C and 280°C. MeasuredδD values — 69 to — 63%0 (SMOW), of inclusion fluid and calculatedδ ¹⁸O values of hydrothermal fluids — 7.5 to — 1.4%0 (SMOW), strongly suggest a meteoric origin for the fluids. The quite consistentδD values and the range inδ ¹⁸O values indicate that major water-rock interaction led to the evolution inδ18O of the hydrothermal fluids.     

Optical and magnetic pulsations

Based on data from the PULSAUR-rocket (1980) and ground observations, a correlation study between optical and magnetic pulsations has been carried out. By use of All-Sky TV along with the measured flux of electrons we have also simulated the ground magnetic field. The simulation is based on a model of pulsating currents caused by conductivity changes in the ionosphere. Our simulated field well represents the observed field. The time delay between the optical and magnetic signal is discussed in relation to our model, and so is the lack of correlation between the high frequency component of the two types of pulsations.     

A low-scattering approximation for the hydrodynamic interactions of small wave-power devices

This paper concerns mathematical modelling of the hydrodynamic interaction forces between small vertically axisymmetric wave-power devices. The model takes into account small-body approximations for the first order scattered waves but neglects multiple scattering. Further, the local wave fields are neglected, making the model inapplicable for very closely spaced bodies.The model, which is called the low-scattering approximation, comprises analytical formulae for the forces in any of the translation modes surge, sway and heave. It requires, however, that the following isolated-body parameters are known or externally supplied: the added mass and the force coefficients for both heave and surge motion.Comparison with accurate numerical results of a two-buoy system indicates that the present approach is fairly good even when the buoy diameter is as large as 1/6 of the wavelength and the buoy spacing is as small as 5 buoy radii.