Predictive modeling of the permafrost thermal regime in Russian railroad subgrade support systems

The goal of a predictive thermotechnical calculation is to model the behavior of the top permafrost boundary under current operational conditions as well as increasing average annual air temperatures that results in degradation of the permafrost layer. Numerical modeling was used to assess the efficient application of construction measures to create sustainable operation of the railroad. The numerical modeling was carried out in the programming complex FEM-models developed by geotechnical engineers of St. Petersburg, Russia under Prof. V. M. Ulitsky’s guidance. The Termoground Program as a part of the FEM-models enables the research of freezing, heaving and thawing in different design solutions. Research was carried out in space resolution for a year cycle. The performed model has shown that the designing measures accepted for permafrost protection from retreat in the subgrade support were generally effective.     

Dynamic of Sea Water Interface using Hydrochemical Facies Evolution Diagram

This paper analyzes the results of a theoretical simulation of sea water intrusion and its dynamics. The assignment of hydrochemical facies identifies whether the aquifer is in the phase of sea water intrusion or freshening, indicating the status of the aquifer in terms of the advance or regression of the saline front. A new multi-rectangular diagram is proposed that aids interpretation of these important processes through the representation and evolution of hydrochemical facies (hydrochemical facies evolution diagram, HFE-D). As an example, the HEF-D is applied to an alluvial aquifer in the Vinaroz-Peñíscola Plain (Spain), where Ca-Cl facies characterize the sea water intrusion phase, while Na-MixHCO₃/MixSO₄ facies characterize a freshening stage.     

Recent geomorphological changes of the middle and lower Calore River (Campania, Southern Italy)

The geomorphological changes experienced by the middle and lower Calore River (Southern Italy) between 1957 and 1998 were investigated. Data derived from field surveys and interpretation of topographic maps and aerial photos were introduced into a geographic information system (GIS) and processed. The results showed that the Calore River underwent a mean narrowing of 66 %, with a peak of 86 %. The channel length increased by approximately 75 m and the sinuosity from 1.311 to 1.314. The extension of fluvial bars reduced by more than 83 %, while their number increased from 151 to 381. Field evidence of riverbed lowering, such as river terraces formed in the considered time span and exhumation of foundations of bridges and flood-walls, were also constantly detected. Due to these channel adjustments, the Calore River morphology changed from transitional to single-thread. These results were coherent with those reported in the pre-existing literature about channel adjustments experienced by many rivers during the twentieth century. They all were explainable with a reduction of the bedload transport; this latter, in turn, is completely in accordance with the environmental changes that affected the Calore River system in the considered period (i.e., damming and/or channelization of the main tributaries, reduction of liquid discharge due to water withdrawals and sediment mining from the riverbed).     

The Influence of the Electron κ-Distribution in the Solar Corona on the Fe VIII – Fe XV Line Intensities

Changes in the excitation equilibrium of Feviii – Fe xv in the solar corona due to the electron non-thermal κ-distribution are studied. The shape of the distribution affects the electron excitation rate and thus the relative intensities of the spectral lines. Since the shape of the electron distribution function influences also the ionization equilibrium of Fe, both effects change the final intensities of the lines. Possibilities for diagnostics of the shape of the electron distribution in the solar corona are discussed. Synthetic spectrum of Fe for T = 1.58× 10⁶ K and n_e = 10⁸ cm⁻³ is shown together with the synthetic spectra computed with DEM for the quiet Sun.     

3D structure of the Earth's crust beneath the northern part of the Bohemian Massif

The SUDETES 2003 wide-angle refraction/reflection experiment covered the area of the south-western Poland and the northern Bohemian Massif. The good quality data that were gathered combined with the data from previous experiments (POLONAISE'97, CELEBRATION 2000) allowed us to prepare a 3D seismic model of the crust and uppermost mantle for this area. We inverted travel times of both refracted and reflected P waves using the JIVE3D package. This allowed us to obtain a model of P-wave velocity distribution as well as the shape of major boundaries in the crust. We also present a detailed uncertainty analysis for both the boundary depths and the velocity field. In doing the uncertainty analysis we found an interesting, strong dependence between uncertainty and inversion scheme (order of used phases). We also compared the model with surface geology and found good correlation between velocity inhomogeneities in the uppermost crust (down to 2 km) and major geological units. The higher velocity lower crust (6.9–7.2 km/s) could result from remelting of the lower crust or magmatic underplating.     

Gas hydrate disturbance fabrics of southern Hydrate Ridge sediments (ODP Leg 204): Relationship with texture and physical properties

Soupy and mousse-like fabrics are disturbance sedimentary features that result from the dissociation of gas hydrate, a process that releases water. During the core retrieval process, soupy and mousse-like fabrics are produced in the gas hydrate-bearing sediments due to changes in pressure and temperature conditions. Therefore, the identification of soupy and mousse-like fabrics can be used as a proxy for the presence of gas hydrate in addition to other evidence, such as pore water freshening or anomalously cool temperature. We present here grain-size results, mineralogical composition and magnetic susceptibility data of soupy and mousse-like samples from the southern Hydrate Ridge (Cascadia accretionary complex) acquired during Leg 204 of the Ocean Drilling Program. In order to study the relationship between sedimentary texture and the presence of gas hydrates, we have compared these results with the main textural and compositional data available from the same area. Most of the disturbed analyzed samples from the summit and the western flank of southern Hydrate Ridge show a mean grain size coarser than the average mean grain size of the hemipelagic samples from the same area. The depositional features of the sediments are not recognised due to disturbance. However, their granulometric statistical parameters and distribution curves, and magnetic susceptibility logs indicate that they correspond to a turbidite facies. These results suggest that gas hydrates in the southern Hydrate Ridge could form preferentially in coarser grain-size layers that could act as conduits feeding gas from below the BSR. Two samples from the uppermost metres near the seafloor at the summit of the southern Hydrate Ridge show a finer mean grain-size value than the average of hemipelagic samples. They were located where the highest amount of gas hydrates was detected, suggesting that in this area the availability of methane gas was high enough to generate gas hydrates, even within low-permeability layers. The mineralogical composition of the soupy and mousse-like sediments does not show any specific characteristic with respect to the other samples from the southern Hydrate Ridge.     

Nonequilibrium Processes in the Solar Corona,Transition Region,Flares, and Solar Wind <Emphasis Type="Italic">(Invited Review)</Emphasis>

We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modeling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for the detection of these non-equilibrium phenomena in various spectral ranges.     

Narrow-band CCD photometry of giant H ii regions

We have obtained accurate CCD narrow-band Hβ and Hα photometry of giant H  ii regions (GEHRs) in M33, NGC 6822 and M101. Comparison with previous determinations of emission-line fluxes shows large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion ( σ ) derived from emission linewidths, we review the     relation. A re-analysis of the properties of the GEHRs included in our sample shows that age spread and the superposition of components in multiple regions introduce a considerable spread in the regression. Combining the information available in the literature regarding ages of the associated clusters, evolutionary footprints on the interstellar medium, and kinematical properties of the knots that build up the multiple GEHRs, we find that a subsample – which we refer to as young and single GEHRs – do follow a tight relation in the     plane.     

Petrological and experimental evidence for differentiation of water-rich magmas beneath St. Kitts,Lesser Antilles

St. Kitts lies in the northern Lesser Antilles, a subduction-related intraoceanic volcanic arc known for its magmatic diversity and unusually abundant cognate xenoliths. We combine the geochemistry of xenoliths, melt inclusions and lavas with high pressure–temperature experiments to explore magma differentiation processes beneath St. Kitts. Lavas range from basalt to rhyolite, with predominant andesites and basaltic andesites. Xenoliths, dominated by calcic plagioclase and amphibole, typically in reaction relationship with pyroxenes and olivine, can be divided into plutonic and cumulate varieties based on mineral textures and compositions. Cumulate varieties, formed primarily by the accumulation of liquidus phases, comprise ensembles that represent instantaneous solid compositions from one or more magma batches; plutonic varieties have mineralogy and textures consistent with protracted solidification of magmatic mush. Mineral chemistry in lavas and xenoliths is subtly different. For example, plagioclase with unusually high anorthite content (An_≤100) occurs in some plutonic xenoliths, whereas the most calcic plagioclase in cumulate xenoliths and lavas are An₉₇ and An₉₅, respectively. Fluid-saturated, equilibrium crystallisation experiments were performed on a St. Kitts basaltic andesite, with three different fluid compositions (XH₂O = 1.0, 0.66 and 0.33) at 2.4 kbar, 950–1025 °C, and fO₂ = NNO ? 0.6 to NNO + 1.2 log units. Experiments reproduce lava liquid lines of descent and many xenolith assemblages, but fail to match xenolith and lava phenocryst mineral compositions, notably the very An-rich plagioclase. The strong positive correlation between experimentally determined plagioclase-melt Kd_Ca–Na and dissolved H₂O in the melt, together with the occurrence of Al-rich mafic lavas, suggests that parental magmas were water-rich (> 9 wt% H₂O) basaltic andesites that crystallised over a wide pressure range (1.5–6 kbar). Comparison of experimental and natural (lava, xenolith) mafic mineral composition reveals that whereas olivine in lavas is predominantly primocrysts precipitated at low-pressure, pyroxenes and spinel are predominantly xenocrysts formed by disaggregation of plutonic mushes. Overall, St. Kitts xenoliths and lavas testify to mid-crustal differentiation of low-MgO basalt and basaltic andesite magmas within a trans-crustal, magmatic mush system. Lower crustal ultramafic cumulates that relate parental low-MgO basalts to primary, mantle -derived melts are absent on St. Kitts.