Quartz deformation mechanisms during Barrovian metamorphism: Implications from crystallographic orientation of different generations of quartz in pelites

The behaviour of quartz during metamorphism is studied based on two case studies from the Barrovian terrains of Sulitjelma in arctic Scandinavia and Loch Tay in the Central Highlands Dalradian of Scotland. Both terrains preserve evidence for metamorphism in pelites involving nucleation and growth of garnet at different times in the deformation history. Data are presented on the size, shape and crystallographic orientation of quartz preserved as inclusions in garnet and as grains in the surrounding matrix. While quartz-grains remain small and dispersed between mica grains, deformation appears to be dominated by grain-boundary sliding accommodated by dissolution–precipitation. At amphibolite facies, textural coarsening occurs by dissolution of small quartz grains and growth of larger quartz grains, coupled with segregation of quartz from mica. As a result, quartz deforms by dislocation creep, developing crystallographic preferred orientations (CPO) consistent with both coaxial and non-coaxial strain. Quartz CPOs with <0001> axes lying parallel to foliation and stretching direction are commonly developed, and best explained by mechanical rotation of inequant (detrital?) quartz grains. There is no evidence for selective entrapment of quartz inclusions in garnet on the basis of quartz crystallographic orientation.     

Space–time distribution of ancient and active alluvial karst subsidence: examples from the central Ebro Basin,Spain

Space and time variations of alluvial karst subsidence in the central Ebro Basin are analysed in trenches (paleodolines), aerial photographs (historical dolines) and field surveys (present-day active dolines). The measured subsidence rates, as well as a comparison between densities of paleodolines computed in randomly selected scan-lines and density of active dolines computed in maps, suggest that present-day subsidence in favourable areas is more intense than that of Pleistocene times. According to diachronic maps drawn from (a) different aerial photographs taken after 1946 and (b) field surveys on deformations in urbanized areas, subsidence behaved as a nearly steady process while the whole area was used for agriculture. In contrast, rapid changes (through periods of several tens of years) have occurred in urbanized areas, in which dolines expand their boundaries through small marginal collapses, shifting sharply their sinking centres to neighbouring sites. These rapid changes do not have an equivalent in observed paleodolines.     

Corrosion behavior of anodic oxidized TiO<Subscript>2</Subscript> film in seawater

TiO₂ films were formed on metallic titanium substrates by the anodic oxidation method in H₂SO₄ solution under the 80V D.C.. Phase component and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions. Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum (EIS) and polarization curves. The result showed that the TiO₂ film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface. The average water contact angle of the film was 116.4° in dark, in contrast to an angle of 42.7° under the UV illumination for 2 hours, which demonstrates good hydrophobic property. The anti-corrosion behavior of the TiO₂ film was declining with the extended immersion time. Under dark conditions, however, the hydrophobic TiO₂ film retarded the water infiltrating into the substrate. The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight. All of those mentioned above indicate that the TiO₂ film possesses much better performance under dark condition, and it can be applied as an engineering material under dark seawater environment.     

From sequential to parallel growth of cities: Theory and evidence from Canada

This paper examines city growth patterns and the corresponding city size distribution evolution over long periods of time using a simple New Economic Geography(NEG) model and urban population data from Canada. The main findings are twofold. First, there is a transition from sequential to parallel growth of cities over long periods of time: city growth shows a sequential mode in the stage of rapid urbanization, i.e., the cities with the best development conditions will take the lead in growth, after which the cities with higher ranks will become the fastest-growing cities; in the late stage of urbanization, city growth converges according to Gibrat′s law, and exhibits a parallel growth pattern. Second, city size distribution is found to have persistent structural characteristics: the city system is self-organized into multiple discrete size groups; city growth shows club convergence characteristics, and the cities with similar development conditions eventually converge to a similar size. The results will not only enhance our understanding of urbanization process, but will also provide a timely and clear policy reference for promoting the healthy urbanization of developing countries.     

Results of monitoring of the changes in the hydrochemical structure of the central and Southern Caspian Sea over 1995–2005

The results of decennial monitoring of the Caspian Sea were summarized, which allowed revealing the “pumping” of nutrients from the euphotic layer to deepwater depressions of the Central and Southern Caspian Sea. In parallel, in the deepwater depressions, growth of hypoxia to values of 0.2–0.5 ml O₂/l proceeds. In 2006, hydrogen sulfide was registered in the near-bottom layer of the South Caspian Sea Basin. It is shown that the transformation of the hydrochemical structure was directed towards the conditions observed at the times of Bruevich (1933–1934), but no complete coincidence has yet been reached.     

Sample treatment with focused ultrasound and bath sonication as a powerful tool for the evaluation of cadmium pollution in estuarine waters

A new sample treatment was developed for the determination of dissolved cadmium in Tagus estuarine waters, based on focused ultrasound in conjunction with small volumes in the extraction steps for Cd pre-concentration. Cadmium was first pre-concentrated using a classical approach (APDC as the complexing agent and MIBK as the organic phase) and then back-extracted into HNO₃ with the aid of focused ultrasound, which reduced the acid concentration by more than one order of magnitude (from 4 to 0.1 mol L^− 3). This sample treatment was accomplished in less than 5 min, using low sample volume (20 mL), and low-volume, low-concentration reagents. The pre-concentration factor used in this work was 25, but different sample/organic volume ratios may be used in order to increase that value. The limit of detection and the limit of quantification in Tagus water samples were 0.03 nmol L^− 1 and 0.1 nmol L^− 3, respectively. Recoveries from spiked Tagus water were higher than 90%. The procedure was validated using the reference estuarine water NRC-SLEW-3. In the solubilization of Cd particulate, bath ultrasonication was used in conjunction with HNO₃ + HCl, followed by H₂O₂, which took about 2 instead of the usual 12 h (cooling included) when high-pressure microwave digestion is used.     

Storminess and vulnerability along the Atlantic coastlines of Europe: analysis of storm records and of a greenhouse gases induced climate scenario

Identification of the distinctive circulation patterns of storminess on the Atlantic margin of Europe forms the main objective of this study; dealing with storm frequency, intensity and tracking. The climatology of the extratropical cyclones that affect this region has been examined for the period 1940–1998. Coastal meteorological data from Ireland to Spain have been linked to the cyclone history for the North Atlantic in the analysis of storm records for European coasts. The study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the North Atlantic Oscillation (NAO). Results indicate a seasonal shift in the wind climate, with regionally more severe winters and calmer summers established. This pattern appears to be linked to a northward displacement in the main North Atlantic cyclone track.

An experiment with the ECHAM4 A-GCM at high resolution (T106) has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region. The experiment consists of (1), a 30-year control time-slice representing present-day equivalent CO₂ concentrations and (2), a 30-year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent CO₂ concentrations. The boundary conditions have been obtained from an atmosphere-ocean coupled OA-GCM simulation at low horizontal resolution. An algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones. For most of the northern part of the study region, covering Ireland and Scotland, results describe the establishment by ca. 2060 of a tendency for fewer but more intense storms.

The impacts of these changes in storminess for the vulnerability of European Atlantic coasts are considered. For low-lying, exposed and ‘soft’ sedimentary coasts, as in Ireland, these changes in storminess are likely to result in significant localised increases in coastal erosion.