Generalized Problem of Two and Four Newtonian Centers

We consider integrable spherical analog of the Darboux potential, which appear in the problem (and its generalizations) of the planar motion of a particle in the field of two and four fixed Newtonian centers. The obtained results can be useful when constructing a theory of motion of satellites in the field of an oblate spheroid in constant curvature spaces.     

The ecosystem of Lake Kenon: past and present (Transbaikal Territory,Russia)

Present-day conditions of the Lake Kenon ecosystem are determined by a combination of natural and anthropogenic factors.We have estimated the effects of a complex of factors on the condition of the abiotic environment and on specific biological components in the lake ecosystem.Change in biogenic load has caused an increase in the role of phytoplankton in the general balance of organic matter during the high-water period.Charophytes are the main dominants of bottom vegetation.Anthropogenic load has caused a decrease in both fish species and fish capacity.The lake application as a water reservoir-cooler has influenced the average annual water mineralization(from 420 mg/L to 530.0 mg/L with a maximum 654 mg/L in 1993) and fluctuations in its hydrochemical composition.The present composition of the lake is sulfate-hydrocarbonate-chloride calcium-sodic-magnesium in character.SO 4 – content is twice as much as the maximum permissible concentration in fishery waters.Water drainage from an ash disposal area to the lake has caused an increase in chemical-element concentrations including the heavy metals.Hg concentration in Perca fluviatilis muscles is 0.5 μg/g dry wt.Thus,understanding directions in the ecosystem of the water reservoir-cooler under changing hydrological conditions will let us forecast the consequences of new combined heat and power plant operation.     

Water retention effects on elastic properties of Opalinus shale

Shales play an important role in many engineering applications such as nuclear waste, CO₂ storage and oil or gas production. Shales are often utilized as an impermeable seal or an unconventional reservoir. For both situations, shales are often studied using seismic waves. Elastic properties of shales strongly depend on their hydration, which can lead to substantial structural changes. Thus, in order to explore shaly formations with seismic methods, it is necessary to understand the dependency of shale elastic properties on variations in hydration. In this work, we investigate structural changes in Opalinus shale at different hydration states using laboratory measurements and X-ray micro-computed tomography. We show that the shale swells with hydration and shrinks with drying with no visible damage. The pore space of the shale deforms, exhibiting a reduction in the total porosity with drying and an increase in the total porosity with hydration. We study the elastic properties of the shale at different hydration states using ultrasonic velocities measurements. The elastic moduli of the shale show substantial changes with variations in hydration, which cannot be explained with a single driving mechanism. We suggest that changes of the elastic moduli with variations in hydration are driven by multiple competing factors: (1) variations in total porosity, (2) substitution of pore-filling fluid, (3) change in stiffness of contacts between clay particles and (4) chemical hardening/softening of clay particles. We qualitatively and quantitatively analyse and discuss the influence of each of these factors on the elastic moduli. We conclude that depending on the microstructure and composition of a particular shale, some of the factors dominate over the others, resulting in different dependencies of the elastic moduli on hydration.     

Entrained Macrocryst Minerals as a Key to the Source Region of Olivine Nephelinites: Humberg, Kaiserstuhl, Germany

Olivine nephelinites commonly contain macrocrysts of olivineand clinopyroxene. Some of these macrocrysts might representfragments of the source region of the host magma transportedto the Earth's surface. If this hypothesis is correct thesefragments can be used to characterize the composition of thesource region and to put constraints on the magma generationprocess. In this study, we investigate the origin of macrocrystsand mineral aggregates from an olivine nephelinite from theKaiserstuhl, Germany. We focus on clinopyroxenes (Cpx), whichcan be divided into three groups. Cpx I is relict Cpx from aggregateswith deformed olivine that is depleted in Ca and characterizedby strong light rare earth element (LREE) fractionation, lowTi/Eu and negative high field strength element (HFSE) anomalies.Its geochemical signature is consistent with formation by carbonatitemetasomatism and with equilibration in the presence of orthopyroxene.Cpx II is Ca-rich Cpx, forming both aggregates with deformedolivine and individual macrocrysts. The LREE, as for Cpx I,are strongly fractionated. Convex REE patterns may be present.The depletion in HFSE is less pronounced. Cpx III is oscillatoryzoned Cpx phenocrysts showing enrichment in Ca, convex REE patternsand no HFSE anomalies. The transition in the trace element abundancesbetween the Cpx of the three groups is gradual. However, CpxI and II did not crystallize from the host magma, as demonstratedby the presence of kink-bands and undulose extinction in theassociated olivine and by the composition of alkali aluminosilicateglass inclusions in Cpx II. Based on the Cpx relationships,we interpret the studied suite of macrocrysts and mineral aggregatesas a mixture of disintegrated fragments of the source regionof the host olivine nephelinite. The process of melt generationwas multi-stage. A primary carbonatite melt ascending from deeperlevels in the mantle, probably from the dolomite–garnetperidotite stability field, reacted with mantle peridotite alongthe solidus ledge in the system lherzolite–CO₂ (< 20–22kbar) and started to crystallize carbonate minerals. Becauseof its low solidus temperature, the resulting carbonate-wehrliteassemblage melted incongruently with the formation of additionalclinopyroxene. The carbonatite melt evolved during crystallizationof carbonate minerals and concomitant incongruent melting ofthe carbonate-wehrlite, accompanied by the segregation of incipientalkali aluminosilicate melts. As a consequence of fast reactionrates in the presence of a carbonatite melt, this process probablytook place under disequilibrium conditions. Further meltingof the assemblage wehrlite + alkali aluminosilicate melt ledto the generation of the olivine nephelinite magma. It entrainedfragments of the wehrlite and brought them to the surface. KEY WORDS: carbonatite; metasomatism; source region; clinopyroxene macrocrysts; wehrlite; olivine nephelinite; Kaiserstuhl     

Woolly rhino discovery in the lower Kolyma River

A nearly complete frozen mummy of a woolly rhinoceros (Coelodonta antiquitatis Blum., 1799) was discovered in a gold mine on the lower reaches of the Kolyma River, north–eastern Siberia. This is the first find of the whole body of woolly rhino in permafrost. A large part of the mummified body was preserved, including the left part of the body, covered by skin, including skin of the head and ear, fore and hind legs. The skull with 2 horns and the lower jaw were also preserved. Most of the internal organs were lost, except the intestines, stomach, and their contents. A rib fragment from this individual was dated by AMS-radiocarbon method to 39,140 ± 390 years BP (OxA-18755). Spore and pollen analyses of the stomach contents indicate that grasses and sagebrushes formed the main part of the diet of C. antiquitatis in this region of Arctic Siberia.     

Oxygen Consumption in Permeable and Cohesive Sediments of the Gulf of Aqaba

Oxygen profiles were measured in the sediments of the Gulf of Aqaba (Red Sea), an oligotrophic marine system affected by episodic seasonal flash floods and intense aeolian dry deposition. Sediment cores were retrieved from shallow (15–45 m), intermediate (250–561 m) and deep (700 m) water sites of south–north and east–west transects. Dissolved oxygen concentrations were measured simultaneously by using microelectrodes and microoptodes immediately after sampling and after transportation. Oxygen penetration depths were found to increase from 2 to 5 mm at the shallow water sites with sandy permeable sediments to 10–21 mm at the deeper sites with cohesive muddy sediments. This increase corresponds to decrease in oxygen diffusive fluxes at the sediment–water interface and oxygen consumption rates with depth. Oxygen consumption rates exhibit local maxima at the oxic–anoxic sediment boundary, which may be attributed to oxygen reduction coupled to oxidation of dissolved Fe(II) and Mn(II) at deep and intermediate water sites and of hydrogen sulfide at shallow water sites. Microelectrodes and microoptodes measurements of cohesive sediments from deep and intermediate water sites yielded similar results. By comparison, the microoptodes displayed more robust measurements than microelectrodes in sandy near-shore sediments. This was attributed to their flexible fiber structure that is less likely to break or to abruptly displace sand particles. After transportation of sediment cores from Eilat to Beer Sheva followed by ≤?24-h storage, no changes in oxygen fluxes and consumption rates were detected.     

Sensitivity of the southern annular mode to greenhouse gas emission scenarios

The leading mode of southern hemisphere (SH) climatic variability, the southern annular mode (SAM), has recently seen a shift towards its positive phase due to stratospheric ozone depletion and increasing greenhouse gas (GHG) concentrations. Here we examine how sensitive the SAM (defined as the leading empirical orthogonal function of SH sea level pressure anomalies) is to future GHG concentrations. We determine its likely evolution for three intergovernmental panel on climate change (IPCC) special report on emission scenarios (SRES) for austral summer and winter, using a multi-model ensemble of IPCC fourth assessment report models which resolve stratospheric ozone recovery. During the period of summer ozone recovery (2000–2050), the SAM index exhibits weakly negative, statistically insignificant trends due to stratospheric ozone recovery which offsets the positive forcing imposed by increasing GHG concentrations. Thereafter, positive SAM index trends occur with magnitudes that show sensitivity to the SRES scenario utilised, and thus future GHG emissions. Trends are determined to be strongest for SRES A2, followed by A1B and B1, respectively. The winter SAM maintains a similar dependency upon GHG as summer, but over the entire twenty-first century and to a greater extent. We also examine the influence of ozone recovery by comparing results to models that exclude stratospheric ozone recovery. Projections are shown to be statistically different from the aforementioned results, highlighting the importance of ozone recovery in governing SAM-evolution. We therefore demonstrate that the future SAM will depend both upon GHG emissions and stratospheric ozone recovery.     

Magnetic resonance sounding applied to aquifer characterization

Magnetic resonance sounding (MRS) is distinguished from other geophysical tools used for ground water investigation by the fact that it measures a magnetic resonance signal generated directly from subsurface water molecules. An alternating current pulse energizes a wire loop on the ground surface and the MRS signal is generated; subsurface water is indicated, with a high degree of reliability, by nonzero amplitude readings. Measurements with varied pulse magnitudes then reveal the depth and thickness of water saturated layers. The hydraulic conductivity of aquifers can also be estimated using boreholes for calibration. MRS can be used for both predicting the yield of water supply wells and for interpolation between boreholes, thereby reducing the number of holes required for hydrogeological modeling. An example of the practical application of MRS combined with two-dimensional electrical imaging, in the Kerbernez and Kerien catchments area of France, demonstrates the efficiency of the technique.     

Traveltime parameters in a tilted elliptical anisotropic medium‡

In this paper, we derive analytical expressions for one‐way and two‐way kinematical parameters in elliptical tilted transverse isotropy media. We show that the homogeneous elliptical tilted transverse isotropy models result in hyperbolic moveout with a reflection point sideslip x₀, which can be considered as an additional traveltime parameter for one‐way wave propagation. For homogeneous elliptical tilted transverse isotropy models we show that the inversion of one‐way traveltime parameters suffers from the ambiguity for large tilts. It is shown that the accuracy of the inversion is sensitive to the error in x₀. We also derive and invert the traveltime parameters for a vertically heterogeneous elliptical tilted transverse isotropy model with a tilt gradually changing with depth. The a priori knowledge of parameter δ is very important for inversion. The wrong choise of this parameter results in significant errors in inverted model parameters.