Soil compaction under different management practices in a Croatian vineyard

The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO₂) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO₂ fluxes were found in INV-GC and NT than in the CT and INV-T treatments.     

Moveout approximation for horizontal transversely isotropic and vertical transversely isotropic layered medium. Part II: effective model‡

We use residual moveouts measured along continuous full azimuth reflection angle gathers, in order to obtain effective horizontal transversely isotropic model parameters. The angle gathers are generated through a special angle domain imaging system, for a wide range of reflection angles and full range of phase velocity azimuths. The estimation of the effective model parameters is performed in two stages. First, the background horizontal transversely isotropic (HTI)/vertical transversely isotropic (VTI) layered model is used, along with the values of reflection angles, for converting the measured residual moveouts (or traveltime errors) into azimuthally dependent normal moveout (NMO) velocities. Then we apply a digital Fourier transform to convert the NMO velocities into azimuthal wavenumber domain, in order to obtain the effective HTI model parameters: vertical time, vertical compression velocity, Thomsen parameter delta and the azimuth of the medium axis of symmetry. The method also provides a reliability criterion of the HTI assumption. The criterion shows whether the medium possesses the HTI type of symmetry, or whether the azimuthal dependence of the residual traveltime indicates to a more complex azimuthal anisotropy. The effective model used in this approach is defined for a 1D structure with a set of HTI, VTI and isotropic layers (with at least one HTI layer). We describe and analyse the reduction of a multi‐layer structure into an equivalent effective HTI model. The equivalent model yields the same NMO velocity and the same offset azimuth on the Earth's surface as the original layered structure, for any azimuth of the phase velocity. The effective model approximates the kinematics of an HTI/VTI layered structure using only a few parameters. Under the hyperbolic approximation, the proposed effective model is exact.     

Hydrographic changes in the Labrador Sea, 1960–2005

The Labrador Sea has exhibited significant temperature and salinity variations over the past five decades. The whole basin was extremely warm and salty between the mid-1960s and early 1970s, and fresh and cold between the late 1980s and mid-1990s. The full column salinity change observed between these periods is equivalent to mixing a 6 m thick freshwater layer into the water column of the early 1970s. The freshening and cooling trends reversed in 1994 starting a new phase of heat and salt accumulation in the Labrador Sea sustained throughout the subsequent years. It took only a decade for the whole water column to lose most of its excessive freshwater, reinstate stratification and accumulate enough salt and heat to approach its record high salt and heat contents observed between the late 1960s and the early 1970s. If the recent tendencies persist, the basin’s storages of salt and heat will fairly soon, likely by 2008, exceed their historic highs.The main process responsible for the net cooling and freshening of the Labrador Sea between 1987 and 1994 was deep winter convection, which during this period progressively developed to its record depths. It was caused by the recurrence of severe winters during these years and in its turn produced the deepest, densest and most voluminous Labrador Sea Water (LSW_1987–1994) ever observed. The estimated annual production of this water during the period of 1987–1994 is equivalent to the average volume flux of about 4.5 Sv with some individual annual rates exceeding 7.0 Sv. Once winter convection had lost its strength in the winter of 1994–1995, the deep LSW_1987–1994 layer lost “communication” with the mixed layer above, consequently losing its volume, while gaining heat and salt from the intermediate waters outside the Labrador Sea.While the 1000–2000 m layer was steadily becoming warmer and saltier between 1994 and 2005, the upper 1000 m layer experienced another episode of cooling caused by an abrupt increase in the air-sea heat fluxes in the winter of 1999–2000. This change in the atmospheric forcing resulted in fairly intense convective mixing sufficient to produce a new prominent LSW class (LSW₂₀₀₀) penetrating deeper than 1300 m. This layer was steadily sinking or deepening over the years following its production and is presently overlain by even warmer and apparently less dense water mass, implying that LSW₂₀₀₀ is likely to follow the fate of its deeper precursor, LSW_1987–1994. The increasing stratification of the intermediate layer implies intensification in the baroclinic component of the boundary currents around the mid-depth perimeter of the Labrador Sea.The near-bottom waters, originating from the Denmark Strait overflow, exhibit strong interannual variability featuring distinct short-term basin-scale events or pulses of anomalously cold and fresh water, separated by warm and salty overflow modifications. Regardless of their sign these anomalies pass through the abyss of the Labrador Sea, first appearing at the Greenland side and then, about a year later, at the Labrador side and in the central Labrador Basin.The Northeast Atlantic Deep Water (2500–3200 m), originating from the Iceland–Scotland Overflow Water, reached its historically freshest state in the 2000–2001 period and has been steadily becoming saltier since then. It is argued that LSW_1987–1994 significantly contributed to the freshening, density decrease and volume loss experienced by this water mass between the late 1960s and the mid 1990s via the increased entrainment of freshening LSW, the hydrostatic adjustment to expanding LSW, or both.     

Rumanová H5 chondrite,Slovaki

Abstract— An H5 chondrite was found near the village of Rumanová, Slovakia. dominant minerals of the meteorite are enstatite, olivine, kamacite, taenite and troilite. The minor minerals are oligoclase, augite, pigeonite, accessory chromite, whitlockite and chlorapatite. The composition of olivine (Fa_19.0) and low-Ca orthopyroxene (Fs_17.0), and the density and chemical composition of the meteorite correspond to those of an H chondrite. Normal zoning of Ni in metal grains and parallel planar fractures in olivine suggest weak shock metamorphism of stage S3. Due to moderate oxidation of metal, iron hydroxides were formed corresponding to weathering stage W2.     

Evaluation of the thermal conductivity of sandstone solid skeleton using the concept of equivalent microstructure

Acta Geotechnica - We evaluate thermal conductivity of the skeleton of porous sandstone from the measurements of the effective thermal conductivities of dry and saturated specimens provided by...     

Evolution of dwarf early-type galaxies – I. Spatially resolved stellar populations and internal kinematics of Virgo cluster dE/dS0 galaxies

Understanding the origin and evolution of dwarf early-type galaxies remains an important open issue in modern astrophysics. Internal kinematics of a galaxy contains signatures of violent phenomena which may have occurred, e.g. mergers or tidal interactions, while stellar population keeps a fossil record of the star formation history; therefore studying connection between them becomes crucial for understanding galaxy evolution. Here, in the first paper of the series, we present the data on spatially resolved stellar populations and internal kinematics for a large sample of dwarf elliptical (dE) and lenticular (dS0) galaxies in the Virgo cluster. We obtained radial velocities, velocity dispersions, stellar ages and metallicities out to 1–2 half-light radii by reanalysing already published long-slit and integral-field spectroscopic data sets using the nbursts full spectral fitting technique. Surprisingly, bright representatives of the dE/dS0 class (   M_B =−18.0  to −16.0 mag) look very similar to intermediate-mass and giant lenticulars and ellipticals: (1) their nuclear regions often harbour young metal-rich stellar populations always associated with the drops in the velocity dispersion profiles; (2) metallicity gradients in the main discs/spheroids vary significantly from nearly flat profiles to −0.9 dex   r ⁻¹_e  , i.e. somewhat three times steeper than for typical bulges; (3) kinematically decoupled cores were discovered in four galaxies, including two with very little, if any, large-scale rotation. These results suggest similarities in the evolutionary paths of dwarf and giant early-type galaxies and call for reconsidering the role of major mergers in the dE/dS0 evolution.     

The Virtual Solar Observatory—A Resource for International Heliophysics Research

The Virtual Solar Observatory (VSO) has been developed to allow researchers, educators, and the general public to access data and images from the major sources of on-line solar data. The VSO substantially reduces the effort required to locate disparate data sets, and removes the need for the user to locate the data and learn multiple interfaces. The VSO provides a single interface to about 60 geographically distributed data sets including space- and ground-based sources. These data sets incorporate several physical variables including magnetic field, intensity, Doppler velocity, etc., and all wavelengths from X-ray to radio. All layers of the sun, from the interior to the corona, are included. In this paper we describe the system and present the interface that the user will encounter. We also discuss future enhancements planned for the system.     

Water losses risk assessment: an example from Carpathian karst

The multipurpose dam and reservoir “Bogovina” in the Crni Timok valley is one of several projects that have been initiated to improve water availability in Serbia. The site and height of the dam were initially proposed without consideration of risk factors such as water leakage or stability of the banks. Later, complex hydrogeological and speleological surveys and tests identified the potential of significant water losses from the reservoir area connected mainly to the karstic aquifer, and the nearby Bogovina cave system. The analyses show that once the reservoir is filled up, groundwater flow currently oriented towards the future reservoir would saturate the upper part of the karstified rocks, reactivate currently unsaturated pathways and form a reverse discharge outside of the reservoir area. In response to these findings, the dam design and technical details have been adapted accordingly: the dam height has been reduced by 9 m, and it is proposed that grouting and consolidation work be conducted both at the foundation of the dam and extensively on the embankments. It was concluded that although the proposed remedial measures cannot guarantee reservoir tightness, they can reduce the risk of large-scale leaking.     

North Atlantic warming: patterns of long-term trend and multidecadal variability

Climate fluctuations in the North Atlantic Ocean have wide-spread implications for Europe, Africa, and the Americas. This study assesses the relative contribution of the long-term trend and variability of North Atlantic warming using EOF analysis of deep-ocean and near-surface observations. Our analysis demonstrates that the recent warming over the North Atlantic is linked to both long-term (including anthropogenic and natural) climate change and multidecadal variability (MDV, ~50–80 years). Our results suggest a general warming trend of 0.031 ± 0.006°C/decade in the upper 2,000 m North Atlantic over the last 80 years of the twentieth century, although during this time there are periods in which short-term trends were strongly amplified by MDV. For example, MDV accounts for ~60% of North Atlantic warming since 1970. The single-sign basin-scale pattern of MDV with prolonged periods of warming (cooling) in the upper ocean layer and opposite tendency in the lower layer is evident from observations. This pattern is associated with a slowdown (enhancement) of the North Atlantic thermohaline overturning circulation during negative (positive) MDV phases. In contrast, the long-term trend exhibits warming in tropical and mid-latitude North Atlantic and a pattern of cooling in regions associated with major northward heat transports, consistent with a slowdown of the North Atlantic circulation as evident from observations and confirmed by selected modeling results. This localized cooling has been masked in recent decades by warming during the positive phase of MDV. Finally, since the North Atlantic Ocean plays a crucial role in establishing and regulating the global thermohaline circulation, the multidecadal fluctuations discussed here should be considered when assessing long-term climate change and variability, both in the North Atlantic and at global scales.