A generalized least-squares family of algorithms for transient dynamic analysis

By use of the generalized least-squares procedure, in conjunction with a finite element approximation in time, a simple three-time-level family of time integration schemes is derived. This results in fourth-order accurate unconditionally stable algorithms and stable eighth-order accurate non-dissipative algorithms. Numerical examples show the accuracy of the proposed schemes in comparison with the Fox-Goodwin formula and Newmark's average acceleration method.     

A Simplified, Accurate and Fast Method for Lithium Isotope Analysis of Rocks and Fluids, and δ7Li Values of Seawater and Rock Reference Materials

We report a new approach to conduct fast and accurate lithium isotope ratio measurements by MC-ICP mass spectrometry after wet chemical sample preparation. In contrast to most previously published methods our MC-ICP-MS set-up did not use a desolvating system to achieve appropriate ion beam intensities and, therefore, was less affected by matrix-induced shifts of the instrumental mass bias. As the total lithium background and build-up in the sample introduction system was low, previous sample residues could be washed out by an extended uptake of the new sample. Elimination of a nitric acid rinse step increased the sample throughput by a factor of two and allowed the instrumental mass bias drift to be tracked more precisely. δ⁷Li values of powdered silicate rock reference materials and seawater obtained in this study revealed good accuracy and an overall analytical uncertainty of typically 0.5‰ (2s). On the basis of a comparison between our lithium isotope data and compiled literature data, we recommend preliminary average δ⁷Li values for seawater (+30.8‰) and several silicate rock reference materials (BHVO-1: +5.0‰; JA-1: +5.6‰; JB-2: +4.8‰). The compilation of published δ⁷Li values for seawater suggests that the observed large lithium isotope differences are due to inter-method and/or interlaboratory bias. Most recently published δ⁷Li values for seawater show little variation and confirm a constant lithium isotope composition (at the sub ‰ level) of seawater in well mixed ocean basins.     

Chosen aspects of sustainable development on the Polish, Czech and German borderland

The shift to market forces in Poland, East Germany and Czech Republic has fundamentally reconfigured its economic geography. In particular, spatial inequalities between neighboring Polish, Czech and German border regions have re-emerged forcefully in response to new values, expectations and preferences. In this paper the example of coal mines illustrates the potency of spatial planning. The abundance of coal mines in the Polish, Czech and German borderland at or near abandonment and their proximity to ecological corridors make them candidates for renewed uses in industry or conservation. Attention will also be given to the main environmental problems caused by wrongly conducted spatial policy on this borderland. Transforming a landscape requires continuation of guidance and financial assistance of the European Union.     

Longitudinal ultrasonic waves in DC electric field

The results of experimental studies of the propagation of longitudinal waves in saturated rock samples in which there is a flow of electric charges are presented. It is shown that the electric field affects elastic parameters in heterophase media by changing their dynamic characteristics. The aim of the study of the effect of electric field on the propagation of elastic waves in saturated porous media was to determine the optimum conditions for this effect, and to construct a set of effective parameters which could be used to increase the effectiveness of seismoacoustic prospecting methods, particularly acoustic logging, and be helpful for developing new methods of increasing the effectiveness of oil extraction from productive wells.     

Effects of climatic changes on anisakid nematodes in polar regions

Anisakid nematodes are common in Antarctic, sub-Antarctic, and Arctic areas. Current distributional knowledge of anisakids in the polar regions is reviewed. Climatic variables influence the occurrence and abundance of anisakids, directly influencing their free-living larval stages and also indirectly influencing their predominantly invertebrate (but also vertebrate) hosts. As these parasites can also be pathogenic for humans, the paucity of information available is a source of additional hazard. As fish are a major human dietary component in Arctic and Antarctic areas, and are often eaten without heat processing, a high risk of infection by anisakid larvae might be expected. The present level of knowledge, particularly relating to anisakid larval stages present in fishes, is far from satisfactory. Preliminary molecular studies have revealed the presence of species complexes. Contemporary climate warming is modifying the marine environment and may result in an extension of time during which anisakid eggs can persist and hatch, and of the time period during which newly hatched larvae remain viable. As a result there may be an increase in the extent of anisakid distribution. Continued warming will modify the composition of the parasitic nematode fauna of marine animals, due to changes in feeding habits, as the warming of the sea and any localised reduction in salinity (from freshwater runoff) can be expected to bring about changes in the species composition of pelagic and benthic invertebrates.     

Spatial distribution of phosphorus forms in sediments in the Gulf of Gdańsk (southern Baltic Sea)

The paper analyses the concentrations of total phosphorus and its forms in sediments from the Gulf of Gdańsk on the basis of studies conducted at 25 sampling sites in 2001–05. The phosphorus speciation analysis was performed by sequential extraction. The extensive spatial variability of P_tot concentrations and speciation was found to be dependent on the physicochemical properties of the sediments, the oxygen conditions in the water and sediments, and the depth of the water column above the sediment surface. In the coastal zone, the sedimentation of riverine suspended matter and the sorption and chemisorption processes exert a considerable influence on P speciation. Over 70% of variation of total phosphorus concentration in sediments in the Gulf of Gdańsk could be explained by changes of proportion of fine fraction of sediments (grain size <0.0625 mm). Maximum P_tot concentrations were recorded in clays and silts in the deep water, stratified part of the Gulf of Gdańsk. In the coastal zone, where sandy sediments are dominant, phosphorus concentrations were much lower; this was due to the considerable dynamics of the bottom water and intensive sea floor transport. P_tot concentrations in the Gulf of Gdańsk sediments ranged from 1.75 to 957.17 μmol g⁻¹ d.w. Of all the forms of phosphorus, the highest concentrations were found for organic phosphorus (Org-P). Of its inorganic forms, the highest concentrations were of phosphorus bound to clay minerals and aluminium oxides (NaOH-P), the lowest ones were of loosely bound phosphorus (NaCl-P). On the basis of determinations of total phosphorus concentrations in sediments of a given type and the available data on the seabed areas covered by particular sediment types in the Gulf of Gdańsk, the mass of total phosphorus in the surficial sediment layer (0–2 cm) was estimated at ca. 15.6×10³ tonnes.     

Slope processes in the High Arctic: a 30‐year‐long record from Spitsbergen

Ten monitoring sites were established in 1986 near the Scottbreen and Renardbreen glaciers (Bellsund, Spitsbergen) in order to determine the rates of gelifluction on raised marine terraces and on talus cones, accumulation on talus cones, and movement of the protalus rampart. The measurements were performed in 1987, 2007 and 2016. The results obtained revealed a very slow rate of changes on the surface of the analysed area. During 30 years, only one out of 84 points where the gelifluction rate was measured was displaced by 15 cm down‐slope. The maximal annual and average gelifluction rates were calculated at 0.5 cm and 0.18 cm a^?1, respectively. Several measurement points did not change their position over the observation period. As shown by the observations, the gelifluction rate largely does not depend on slope inclination. Studies of talus cones allowed the level of cone increment to be determined as 314.3 kg of scree per square metre. Analysis of factors influencing the rate of mass movement allowed for correlation of the small‐scale gelifluction movement at the analysed sites with the general trends of climate warming. In this part of the Arctic, these trends are manifested by soil desiccation. It appears that slope processes depend on very local topoclimatic factors. Analysis of the obtained data with regard to palaeogeographical and climatic investigations suggests that the ice segregation forms on raised marine terraces developed during the last Holocene cooling, i.e. the Little Ice Age.     

Comparison of continuous and discontinuous constitutive models to simulate concrete behaviour under mixed‐mode failure conditions

The paper presents detailed FE simulation results of concrete elements under mixed‐mode failure conditions according to the so‐called shear‐tension test by Nooru‐Mohamed, characterized by curved cracks. A continuous and discontinuous numerical two‐dimensional approach was used. In order to describe the concrete's behaviour within continuum mechanics, two different constitutive models were used. First, an elasto‐plastic model with isotropic hardening and softening was assumed. In a compression regime, a Drucker–Prager criterion with a non‐associated flow rule was used. In turn, in a tensile regime, a Rankine criterion with an associated flow rule was adopted. Second, an isotropic damage constitutive model was applied with a single scalar damage parameter and different definitions of the equivalent strain. Both constitutive laws were enriched by a characteristic length of micro‐structure to capture properly strain localization. As an alternative approach, the extended finite element method was used. Our results were compared with the experimental ones and with results of other FE simulations reported in the literature. Copyright © 2015 John Wiley & Sons, Ltd.