LU Vel (GJ 375): A M3.5Ve Flare and Double-Lined Spectroscopic Binary

High resolution echelle spectroscopic observations taken with the FEROS spectrograph at the 2.2 m telescope ESO confirm the binary nature of the flare M3.5V star LU Vel (GJ 375, RE J0958-462) previously reported by Christian and Mathioudakis (2002). Emission of similar intensity from both components is detected in the Balmer, Na i D₁&D₂, He i D₃, Ca ii H&K, and Ca ii IRT lines. We have determined precise radial velocities by cross correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of the system. The binary consists of two near-equal M3.5V components with an orbital period shorter than 2 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics.     

Equilibrium constants of triethanolamine in major seawater salts

Acid–base equilibrium constants of triethanolamine (TEA) have been determined by potentiometric titrations with a glass electrode, at 25 °C. Ionic strength was kept constant with only one electrolyte (using one of these salts: NaCl, KCl, MgCl₂ or CaCl₂), with binary mixtures of MgCl₂ and CaCl₂, and finally, in a solution with a composition approximately similar to that of natural seawater without sulfate. Equilibrium constants have been expressed in function of ionic strength by means of Pitzer equations and interaction parameters proposed in this theory have been obtained. It has been found that acid–base behaviour of TEA depends greatly on the salt used: basicity of TEA is decreased by CaCl₂, while it is increased by the other electrolytes used in this work.     

Geodetic intersection on the ellipsoid

Through each of two known points on the ellipsoid a geodesic is passing in a known azimuth. We solve the problem of intersection of the two geodesics. The solution for the latitude is obtained as a closed formula for the sphere plus a small correction, of the order of the eccentricity of the ellipsoid, which is determined by numerical integration. The solution is iterative. Once the latitude is obtained, the longitude is determined without iteration.     

9000 years of changes in peat organic matter composition in Store Mosse (Sweden) traced using FTIR-ATR

Store Mosse (the ‘Great Bog’ in Swedish) is one of the most extensive bog complexes in southern Sweden (~77 km²), where pioneering palaeoenvironmental research has been carried out since the early 20th century. This includes, for example, vegetation changes, carbon and nitrogen dynamics, peat decomposition, atmospheric metal pollution, mineral dust deposition, dendrochronology, and tephrochronology. Even though organic matter (OM) represents the bulk of the peat mass and its compositional change has the potential to provide crucial ecological information on bog responses to environmental factors, peat OM molecular composition has not been addressed in detail. Here, a 568-cm-deep peat sequence was studied at high resolution, by attenuated reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) in the mid-infrared region (4000–400 cm^–1). Principal components analysis was performed on selected absorbances and change-point modelling was applied to the records to determine the timing of changes. Four components accounted for peat composition: (i) depletion/accumulation of labile (i.e. carbohydrates) and recalcitrant (i.e. lignin and other aromatics, aliphatics, organic acids and some N compounds) compounds, due to peat decomposition; (ii) variations in N compounds and carbohydrates; (iii) residual variation of lignin and organic acids; and (iv) residual variation of aliphatic structures. Peat decomposition showed two main patterns: a long-term trend highly correlated to peat age (r = 0.87), and a short-term trend, which showed five main phases of increased decomposition (at ~8.4–8.1, ~7.0–5.6, ~3.5–3.1, ~2.7–2.1 and ~1.6–1.3 ka) – mostly corresponding to drier climate and its effect on bog hydrology. The high peat accumulation event (~5.6–3.9 ka), described in earlier studies, is characterized by the lowest degree of peat decomposition of the whole record. Given that FTIR-ATR is a quick, non-destructive, cost-effective technique, our results indicate that it can be applied in a systematic way (including multicore studies) to peat research and provide relevant information on the evolution of peatlands.     

On the topographic bias in geoid determination by the external gravity field

The topographic bias is defined as the error/bias committed by continuing the external gravity field inside the topographic masses by a harmonic function. We study the topographic bias given by a digital terrain model defined by a spherical template, and we show that the topographic bias is given only by the potential of an inner-zone cap, and it equals the bias of the Bouguer shell, independent of the size of the cap. Then we study the effect on the real Earth by decomposing its topography into a template, and we show also in this case that the topographic bias is that of the Bouguer shell, independent of the shape of the terrain. Finally, we show that the topographic potential of the terrain at the geoid can be determined to any precision by a Taylor expansion outside the Earth’s surface. The last statement is demonstrated by a Taylor expansion to fourth order.     

Adsorption of cobalt by using inorganic components of sediment samples from water bodies

The adsorption of cobalt ions was evaluated using sediment samples from water bodies to investigate the adsorption properties of sediment and the behavior of these natural materials in the presence of nuclear and industrial waste.The two sediments(S1 and S2)were treated to eliminate humic and fulvic acids and then they were characterized by several techniques.The minerals found in both the sediments(X-ray diffraction)were quartz and albite;plus,goethite and muscovite in S1,and kaolinite and montmorillonite in S2.Point of zero charge(PZC)of S1 and S2 was 6.00 and 5.22,respectively.The specific area of S1(63.3 m²/g)is higher than S2(1.5 m²/g).Adsorption kinetics data for S1 and S2 were best fitted to the pseudo second-order model.The removal efficiency of S1 for cobalt was 96%with an adsorption capacity(qe)of 0.93 mg/g,and for S2 was 45%with a qeof 0.40 mg/g.The experimental data of the adsorption isotherms were adjusted to Langmuir and Freundlich models for S1 and S2,respectively.The thermodynamic parameters(enthalpy,entropy,and Gibb’s free energy)indicated that the adsorption processes were endothermic,spontaneous,and chemisorption mechanism.The results show that the adsorption capacities of the sediments depend on their composition.These water sediments have important adsorption properties for cobalt,and they can be used in the treatment of nuclear and industrial aqueous wastes.     

Magnetostratigraphy in the vicinity of the cretaceous-tertiary boundary in Limhamn,southern Sweden

Summary A magnetostratigraphic subdivision of the Danian and Upper Maastrichtian at Limhamn, souternmost Sweden, based upon 63 samples from drill cores (only up and down is known), is proposed. The boundary between the Maastrichtian and the Danian — situated in chron 29R — was determined by means of nanofossils. It is marked by a hardground surface indicating a hiatus with an estimated duration of 100 ka. The presence of chron 28R at the top of the Limhamn rock sequence and chron 30R in the Maastrichtian is indicated by single samples with reversed polarity. Net sedimentation rates have been calculated on the basis of the proposed magnetochronozones. the highest net sedimentation rate is found in the Danian part of chron 29R.     

Temperature dependence of calcite dissolution kinetics between 1 and 62°C at pH 2.7 to 8.4 in aqueous solutions

The kinetics of calcite dissolution in aqueous KCl-solutions far from equilibrium, between 1 and 62°C in the pH-range 2.7 to 8.4 have been investigated using a rotating disc apparatus. At neutral and alkaline pH in the mixed kinetic regime the empirical apparent activation energy (EAAE) for the surface chemical reaction rate constant is 54 ± 4 kJ mole^?1 for Carrara marble and 46 ± 4 kJ mole^?1 for Iceland spar. Under similar conditions the EAAE of the transport rate constant increases with decreasing temperature, but has a mean value of 27 ± 2 kJ mole^?1. The corresponding diffusion coefficient has a mean EAAE of 37 ± 3 kJ mole^?1 and this high EAAE is consistent with transport dependence on product diffusion in this H⁺-independent regime.In contrast, in acid solutions, where the rate approaches end-member transport control, the EAAE of the diffusion coefficient is 16 kJ mole^?1, also decreasing with increasing temperature. This is compatible with H⁺-diffusion to the surface being rate-controlling.In inhibitor-free natural systems, calcite dissolution kinetics far from equilibrium can be described in terms of three regimes: an H⁺-dependent regime (pH < 4 at 25°C), a transition regime (4 < pH < 5.5 at 25°C) and an H⁺-independent regime (pH > 5.5 at 25°C). At lower temperatures these boundaries move to higher pH values. The presence of inhibitors in natural systems may enhance surface controlled kinetics.     

Topographic and atmospheric corrections of gravimetric geoid determination with special emphasis on the effects of harmonics of degrees zero and one

 The topographic and atmospheric effects of gravimetric geoid determination by the modified Stokes formula, which combines terrestrial gravity and a global geopotential model, are presented. Special emphasis is given to the zero- and first-degree effects. The normal potential is defined in the traditional way, such that the disturbing potential in the exterior of the masses contains no zero- and first-degree harmonics. In contrast, it is shown that, as a result of the topographic masses, the gravimetric geoid includes such harmonics of the order of several centimetres. In addition, the atmosphere contributes with a zero-degree harmonic of magnitude within 1 cm. Received: 5 November 1999 / Accepted: 22 January 2001