Sibsonian and non-Sibsonian natural neighbour interpolation of the total electron content value

In radioastronomy the interferometric measurement between radiotelescopes located relatively close to each other helps removing ionospheric effects. Unfortunately, in case of networks such as LOw Frequency ARray (LOFAR), due to long baselines (currently up to 1500 km), interferometric methods fail to provide sufficiently accurate ionosphere delay corrections. Practically it means that systems such as LOFAR need external ionosphere information, coming from Global or Regional Ionospheric Maps (GIMs or RIMs, respectively). Thanks to the technology based on Global Navigation Satellite Systems (GNSS), the scientific community is provided with ionosphere sounding virtually worldwide. In this paper we compare several interpolation methods for RIMs computation based on scattered Vertical Total Electron Content measurements located on one thin ionospheric layer (Ionospheric Pierce Points—IPPs). The results of this work show that methods that take into account the topology of the data distribution (e.g., natural neighbour interpolation) perform better than those based on geometric computation only (e.g., distance-weighted methods).     

全球热液场的分布

岩浆平衡假设认为岩浆供给的变化是大尺度上控制大洋扩张脊热液场分布模式主要因素。这个理论较为简单,但是一些因素的存在使得验证这个假设较为复杂,如热通量测量的匮乏、岩浆作用与热液作用在时间上的延迟、渗透率的作用、非岩浆热源以及热液场勘探的不确定性。在此,为了验证这个理论,我们总结目前全球活动热液场分布的认识。目前,已发现的活动热液场大约有280个,约为预计数量（1000）的四分之一。到目前为止,大约占全球洋脊20％的部分已经开展了以寻求活动热液场为目的的勘探活动,但是其中仅一半积累了足够多的数据进行统计分析处理。根据11个总长度为6140km的洋脊段数据,我们发现在热液场频率或者热液羽状流发生率与岩浆平衡之间存在强烈的线性关系,其中岩浆平衡是通过洋壳的厚度推算得出。对于扩张速率在10—150mm／yr之间的洋脊,这种线性关系强烈支持岩浆平衡假设。次级的控制因素包括渗透率和深大断裂所提供的额外热量,其中渗透率的影响随着扩张速率的减小而增强,而深大断裂所提供的热量则可以通过以下几种方式获得：上地幔的直接冷却,辉长岩侵入体的冷却以及下覆超镁铁质岩的蛇纹岩化作用。初步的观测以及理论表明在受热点影响的洋脊热液活动相当贫乏,然而数据缺乏妨碍了认识的获得。虽然我们的全部结论来自于详细研究热液场的频率,特别是在慢速扩张洋脊,但也与全球海洋^3He（一种可靠的岩浆指示剂）的分布一致。     

European glacial relict snails and plants: environmental context of their modern refugial occurrence in southern Siberia

Knowledge of present‐day communities and ecosystems resembling those reconstructed from the fossil record can help improve our understanding of historical distribution patterns and species composition of past communities. Here, we use a unique data set of 570 plots explored for vascular plant and 315 for land‐snail assemblages located along a 650‐km‐long transect running across a steep climatic gradient in the Russian Altai Mountains and their foothills in southern Siberia. We analysed climatic and habitat requirements of modern populations for eight land‐snail and 16 vascular plant species that are considered characteristic of the full‐glacial environment of central Europe based on (i) fossil evidence from loess deposits (snails) or (ii) refugial patterns of their modern distributions (plants). The analysis yielded consistent predictions of the full‐glacial central European climate derived from both snail and plant populations. We found that the distribution of these 24 species was limited to the areas with mean annual temperature varying from ?6.7 to 3.4 °C (median ?2.5 °C) and with total annual precipitation varying from 137 to 593 mm (median 283 mm). In both groups there were species limited to areas with colder and drier macroclimates (e.g. snails Columella columella and Pupilla loessica, and plants Kobresia myosuroides and Krascheninnikovia ceratoides), whereas other species preferred areas with relatively warmer and/or moister macroclimates (e.g. snails Pupilla turcmenica and P. alpicola, and plants Artemisia laciniata and Carex capillaris). Analysis of climatic conditions also indicated that distributional shifts of the studied species during the Pleistocene/Holocene transition were closely related to their climatic tolerances. Our results suggest that the habitat requirements of southern Siberian populations can provide realistic insights into the reconstruction of Eurasian, especially central European, glacial environments. Data obtained from modern populations also highlight the importance of wet habitats as refugia in the generally dry full‐glacial landscape.     

Dissolved and particulate organic carbon in hydrothermal plumes from the East Pacific Rise, 9°50′N

Chemoautotrophic production in seafloor hydrothermal systems has the potential to provide an important source of organic carbon that is exported to the surrounding deep-ocean. While hydrothermal plumes may export carbon, entrained from chimney walls and biologically rich diffuse flow areas, away from sites of venting they also have the potential to provide an environment for in-situ carbon fixation. In this study, we have followed the fate of dissolved and particulate organic carbon (DOC and POC) as it is dispersed through and settles beneath a hydrothermal plume system at 9°50′N on the East Pacific Rise. Concentrations of both DOC and POC are elevated in buoyant plume samples that were collected directly above sites of active venting using both DSV Alvin and a CTD-rosette. Similar levels of POC enrichment are also observed in the dispersing non-buoyant plume, ∼500 m downstream from the vent-site. Further, sediment-trap samples collected beneath the same dispersing plume system, show evidence for a close coupling between organic carbon and Fe oxyhydroxide fluxes. We propose, therefore, a process that concentrates POC into hydrothermal plumes as they disperse through the deep-ocean. This is most probably the result of some combination of preferential adsorption of organic carbon onto Fe-oxyhydroxides and/or microbial activity that preferentially concentrates organic carbon in association with Fe-oxyhydroxides (e.g. through the microbial oxidation of Fe(II) and Fe sulfides). This potential for biological production and consumption within hydrothermal plumes highlights the importance of a multidisciplinary approach to understanding the role of the carbon cycle in deep-sea hydrothermal systems as well as the role that hydrothermal systems may play in regulating global deep-ocean carbon budgets.     

A Numerical–Analytical Approach to Modeling the Axial Rotation of the Earth

A model for the non-uniform axial rotation of the Earth is studied using a celestial-mechanical approach and numerical simulations. The application of an approximate model containing a small number of parameters to predict variations of the axial rotation velocity of the Earth over short time intervals is justified. This approximate model is obtained by averaging variable parameters that are subject to small variations due to non-stationarity of the perturbing factors. The model is verified and compared with predictions over a long time interval published by the International Earth Rotation and Reference Systems Service (IERS).     

Frühdiagenetische allochthone Zementation mariner Küsten-Sande durch evaporitische Calcit-Ausscheidung im Gebiet der Kanarischen Inseln

Zusammenfassung Auf den Inseln Fuerteventura und Lobos (Kanarische Inseln) treten Mg-reiche Kalkarenite im Gezeitenbereich der Küstenregion auf, die durch evaporitische Abscheidung von Calcit auf den Kornoberflächen von lockerem Kalksand (bestehend aus Mg-reichem Calcit, Aragonit und Calcit) mit nichtkarbonatischem Anteil (Gesteinsfragmente, Pyroxene, Olivin, Magnetit, Hämatit) gebildet wurden.Die Porosität ist im Vergleich zu den unverfestigten Küstensanden deutlich niedriger, die Zahl der Kornkontakte hat zugenommen, und bei den Kalkareniten von Fuerteventura tritt bereits eine geringe Zahl von konkav-konvexen Kontakten auf, die auf eine geringe mechanische Beanspruchung des Gesteins hindeuten.Ähnliche Gesteine sind aus dem gleichen Bildungsbereich von Süd-Florida und dem Persischen Golf bekannt.Teil 1 Mineralogisch-sedimentpetrographischer Untersuchungen an rezenten Sedimenten im Bereich der Kanarischen Inseln.Herrn Prof. Dr.Carl W. Correns zum 70. Geburtstag gewidmet.     

Mercury Input and Distribution in the Ecosystem Elements of the Sheksna Reservoir

Hg input into the ecosystem elements of the Sheksna Reservoir is studied. The accumulation and distribution of Hg in water, bottom sediment, fish, and snow falling onto the reservoir surfaces are considered. The distribution of Hg in water, bottom sediment, and snow is found to be specially nonuniform. The main sources of Hg are shown to be atmospheric precipitation and surface runoff from the watershed. The regularities of Hg accumulation in fish in different parts of the reservoir are studied.     

Hf and Nd isotopes in marine sediments: Constraints on global silicate weathering

The combined use of Lu–Hf and Sm–Nd isotope systems potentially offers a unique perspective for investigating continental erosion, but little is known about whether, and to what extent, the Hf–Nd isotope composition of sediments is related to silicate weathering intensity. In this study, Hf and Nd elemental and isotope data are reported for marine muds, leached Fe-oxide fractions and zircon-rich turbidite sands collected off the Congo River mouth, and from other parts of the SE Atlantic Ocean. All studied samples from the Congo fan (muds, Fe-hydroxides, sands) exhibit indistinguishable Nd isotopic composition (ε_Nd ~ ? 16), indicating that Fe-hydroxides leached from these sediments correspond to continental oxides precipitated within the Congo basin. In marked contrast, Hf isotope compositions for the same samples exhibit significant variations. Leached Fe-hydroxide fractions are characterized by ε_Hf values (from ? 1.1 to + 1.3) far more radiogenic than associated sediments (from ? 7.1 to ? 12.0) and turbidite sands (from ? 27.2 to ? 31.6). ε_Hf values for Congo fan sediments correlate very well with Al/K (i.e. a well-known index for the intensity of chemical weathering in Central Africa). Taken together, these results indicate that (1) silicate weathering on continents leads to erosion products having very distinctive Hf isotope signatures, and (2) a direct relationship exists between ε_Hf of secondary clay minerals and chemical weathering intensity.These results combined with data from the literature have global implications for understanding the Hf–Nd isotope variability in marine precipitates and sediments. Leached Fe-hydroxides from Congo fan sediments plot remarkably well on an extension of the ‘seawater array’ (i.e. the correlation defined by deep-sea Fe–Mn precipitates), providing additional support to the suggestion that the ocean Hf budget is dominated by continental inputs. Fine-grained sediments define a diffuse trend, between that for igneous rocks and the ‘seawater array’, which we refer to as the ‘zircon-free sediment array’ (ε_Hf = 0.91 ε_Nd + 3.10). Finally, we show that the Hf–Nd arrays for seawater, unweathered igneous rocks, zircon-free and zircon-bearing sediments (ε_Hf = 1.80 ε_Nd + 2.35) can all be reconciled, using Monte Carlo simulations, with a simple weathering model of the continental crust.     

MEMS enablement and analysis of the miniature autonomous submersible explorer

The miniature autonomous submersible explorer (MASE) was designed as a vehicle for astrobiology science by Behar et al. . This paper focuses on the MASE concept and extrapolates a future design based on microelectromechanical systems (MEMS), multifunctional microsystems (MMS), and three-dimensional multichip modules (3-D-MCM). Miniaturization of the electronics increases the payload volumes and power capabilities significantly and this is the main rationale for pursuing extreme miniaturization. The original MASE vehicle accommodated 1-2 instruments while the MEMS enhanced miniature autonomous submersible explorer (MEMSEMASE) accommodates up to six instruments. It is shown that the occupied area of the electronics components is reduced eight times, and the volume 25 times. The vehicle is shaped as a tube with 5 cm in diameter and 20 cm in length and can support 8 W continuously over 5 h. The maximum range is 25 km while the typical onboard instrumentation is conductivity, temperature, depth (CTD), and a high resolution camera. An optical fiber is used for bidirectional communication with the vessel. The goal of this enriched concept is to present an extremely miniaturized submersible design. The vehicle volume is defined to fit inside host vehicles with the goal of future deployment on Europa, oceans on Earth, and bore holes. The paper will focus on showing how electronics can be densely packed into micromachined silicon modules and how these can be designed and interconnected theoretically.