Diurnal asymmetry in the lower ionosphere — seasonal variability

Summary On the basis of long period measurements of ionospheric absorption in five A3 circuits in Central Europe, it is shown that the considerable seasonal variation of the diurnal asymmetry of absorption, found in[1], exhibits practically no year-to-year variability and is well-developed at equivalent frequencies f _eq 1 MHz, while it vanishes at F _eq 2 MHz. The limited data on the diurnal asymmetry of the D-region electron concentration are consistent with the seasonal pattern of the diurnal asymmetry in absorption. A tentative hypothesis of nitric oxide variability as the cause of the seasonal variation of the asymmetry is proposed.     

Variations in the Earth's rotation and crustal deformations

a mmuu ¶rt; ¶rt;au nm u , a auauu ma mu au u. aamuam m¶rt; a, ma u mua mu ¶rt;au u ¶rt;aa u uma a; m a mu ¶rt;auu m ¶rt;muam 10% m ¶rt;au, a u nuuau m .     

Geostationary satellites and variations in the position of the Earth's mass center

¶rt;am m unau a¶rt;umaua m nu ma a u mum u au. am a uu u ma a a umaua nmua mmu ¶rt; u mu m uauu.

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Presented at the Meeting SSG 5.49 of the IAG, Uppsala, August 7, 1978.     

A comparison of anthropogenic mercury pollution in Kastela Bay (Croatia) with pristine estuaries in Ore (Sweden) and Krka (Croatia)

Anthropogenic mercury pollution was studied in Kastela Bay (Croatia), 10 years after chloralkaline plant (PVC) stopped production. The concentration of total mercury determined in sediments which are composed mainly of calcite and quartz, are in the range 14,280-30,400 ng/g. The values are higher than reported in the literature for Elbe and Seine estuaries and also above 25,000 ng/g used for criterion in remediation project in Minamata Bay. The concentration of methylmercury 6.05-36.74 ng/g are typical for slightly to highly contaminated estuarine sediments. The low ratio of methylmercury to total mercury found in sediments of Kastela Bay is in the range 0.04-0.18%. It can be explained that in this region predominate conditions which do not promote in-situ methylation. Sediments were found to be highly anoxic. Concentrations of total mercury in unfiltered surface waters are in the range 69-145 ng/l and in unfiltered bottom waters in the range 230-1,418 ngl(-1). High concentrations found in bottom waters suggest that either resuspension or partial dissolution of sediments takes place. An experiment performed on filtered and unfiltered waters showed that about 85% of total mercury in surface water and almost 100% in bottom water was retained on 45 microm filters. To demonstrate contrasts, two pristine estuaries from norths and south Europe were studied. Silicious sediments of Ore estuary (Sweden) and calcareous sediments of Krka estuary (Croatia) have total mercury concentrations close to accepted background level. The ratio of methylmercury to total mercury is < or = 1% in all samples with one exception. The highest observed ratio (2.70%) was in the surface sediment from E2 station in Krka estuary measured in March 2000. This location is suitable for studying methylmercury formation in pristine environment.     

Distribution of some elements in surface soil over the Kavadarci region,Republic of Macedonia

The results of a first systematic study of spatial distribution of different elements in surface soil over of the Kavadarci region, Republic of Macedonia, known for its nickel industrial activity are reported. The investigated region (360 km²) is covered by a sampling grid of 2 × 2 km²; whereas the sampling grid of 1 × 1 km² was applied in the urban zone and around the ferronickel smelter plant (117 km²). In total 344 soil samples from 172 locations were collected. At each sampling point soil samples were collected at two depths, topsoil (0–5 cm) and bottom soil (20–30 cm). Inductively coupled plasma-mass spectrometry (ICP-MS) was applied for the determination of 36 elements (Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mn, Na, Mg, Mo, Ni, P, Pb, S, Sb, Sc, Se, Sr, Th, Tl, Ti, U, V, W and Zn). Data analysis and construction of maps were performed using the Paradox (ver. 9), Statistica (ver. 6.1), AutoDesk Map (ver. 2008) and Surfer (ver. 8.09) software. Four geogenic and three anthropogenic geochemical associations were established. Within the research, natural and anthropogenic enrichment with heavy metals was determined. Principally, the natural enrichment is related especially to Ni. Pollution by As, Cd, Co, Cr, Cu, Hg, Mo, Pb and Zn is basically insignificant.     

Seismic hazard assessments for two test areas — ‘Southern Italy’ and ‘Belgium—The Netherlands—Germany’

Within the activity of the ESC Subcommission 8 Engineering Seismology, Project TERESA, seismic hazard calculations have been performed for two areas of a different earthquake activity. Fundamental seismological data (earthquake catalogues, macroseismic observations and maps) and some additional geological information were analyzed and processed to prepare inputs for hazard computations. Great attention has been paid to verifying the reliability of the input data. Seismic hazards obtained for five sites of the region of high seismic activity (Sannio-Matese, southern Italy) and six sites of the region of low seismic activity (Brabant Massif and northern Rhine, Belgium—The Netherlands—Germany) are presented and discussed.     

Organic and inorganic geochemistry of Ljubija siderite deposits,NW Bosnia and Herzegovina

The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as siderite–sulfides veins in shale. Three principal types of ore textures have been recognized including massive dark siderite and ankerite, siderite with zebra texture, and siderite veins. The ore and host rocks have been investigated by a combination of inorganic (major, trace, and rare earth element concentrations), organic (characterization of hydrocarbons including biomarkers), and stable isotope geochemical methods (isotope ratios of carbonates, sulfides, sulfates, kerogen, and individual hydrocarbons). New results indicate a marine origin of the host carbonates and a hydrothermal–metasomatic origin of the Fe mineralization. The differences in ore textures (e.g., massive siderite, zebra siderite) are attributed to physicochemical variations (e.g., changes in acidity, temperature, and/or salinity) of the mineralizing fluids and to the succession and intensity of replacement of host limestone. Vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization. The equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites (around 245°C) then for siderite vein (around 185°C). Sulfur isotope ratios suggest Permian seawater or Permian evaporites as the main sulfur source. Fluid inclusion composition confirms a contribution of the Permian seawater to the mineralizing fluids and accord with a Permian mineralization age. Organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal–metasomatic origin of the Ljubija iron deposits.     

The effect of uniaxial elastic deformation on the remanent magnetization of basalts

Summary The effect of uniaxial elastic deformation on the remanent magnetization of some basalts, containing generalized titanomagnetities of different chemical composition, was studied. The irreversible changes of the saturated and natural remanent magnetizations were measured. With the deformed samples no permanent change of the spectrum of micro-coercive forces, or change in the magnitude of the specific saturated remanent magnetization were observed. The experimental results agree with the model of mutual interaction of structural defects with magnetic domatins [10] under the assumption of predominantly reversible changes of the dislocation structure of the sample due to elastic deformation.     

Are prominent mountains frequently mentioned in text? Exploring the spatial expressiveness of text frequency

Data-driven GIScience shows a growing interest in making spatial information from large text data. In this paper, we quantify and thus evaluate the relation between text frequency and properties of the outer-text, geographic setting by comparing text frequencies of mountain names to the respective geomorphometric characteristics. We focus on some 2000 unique mountain names that appear some 50,000 times in a large compilation of texts on Swiss alpine history. The results on the full data set suggest only a weak relation: only 5–10% of the variation in the text frequency being explained by the respective geomorphometric characteristics. However, an analysis of multiple scales allows us to identify a Simpson’s Paradox. What appears to be ‘noise’ in the analysis of all mountains in the whole of Switzerland shows significant local signals. Small spatial extents, found all over Switzerland, can show considerably strong correlations between text frequency and spatial prominence, with up to 90% of the total variation explained. We argue that our findings have practical implications for data-driven GIScience. Retrieving meaningful spatial information from text might only be possible if the spatial scale of analysis reflects the spatial scale described in the input text documents.     

Synthesis and characterization of high-pressure and high-temperature sphene (CaTiSiO5)

Sphene (CaTiSiO₅), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO₃, TiO₂ and SiO₂ using vibro-milling for homogenization and activation of precursors. During the high-pressure and high-temperature synthesis (HPS) process at 4 GPa and 1,200 °C, sphene undergoes into phase transition, from room-temperature phase P2₁ /a to high-temperature phase A2/a. Evidence of that structural phase transition is given in this paper using infrared, Raman spectroscopy and X-ray powder diffraction. Rietveld refinement was employed to get the structural information of the synthesized powder. The most important structural change due to phase transition, the disappearance of the characteristic out-of-center distortion of the Ti atom and moving to the center of octahedra, was confirmed. HPS is an effective method for producing full-dense ceramics without any additives. Reduction of particle size occurred during high-pressure compaction. Microstructure and particle size of both phases were analyzed by scanning electron microscopy.